Below are answers to some of the most common questions we have been asked about the SARS CoV-2 virus and the COVID-19 disease it causes. These answers are provided by our infectious disease faculty experts. We add a new answers weekly. To stay informed, please consider bookmarking this page. 

The most popular of these questions are also being addressed in video form here.

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Unfortunately, a vaccine is still another 12 to 18 months away. In the last few weeks, several groups around the world have developed promising vaccine ‘candidates”. However, those candidates will now have to go through a series of trials with increasing numbers of volunteers, both healthy and sick with COVID-19, to test whether they are both safe and effective. An effective vaccine may keep people from getting COVID-19 a second time entirely, or prevent people from getting severe disease. Once a safe, effective vaccine is developed, it can then take several months to scale-up production of a vaccine and get it distributed.

A recent study showed that the virus can live on hard, smooth surfaces like metal and glass for up to three days and on cardboard for up to 24 hours. So, this is why, cleaning surfaces with alcohol based cleaner, washing your hands frequently and not touching your face can help to reduce the transmission of the virus. Social distancing is also effective at limiting your contact with contaminated surfaces touched by others in public spaces. An even more recent study shows that virus can remain intact on fabric for up to two days. If you are working outside the home and having contact with lots of people, it is best to change your clothes upon arrival home, and wash them in warm/hot water. This is standard practice for people working in the healthcare industry and probably a good behavior for members of the public to adopt for a while.

We have no evidence of people getting infected from packages, however, given that virus can survive on cardboard for up to a day, it is best to take some precautions. When a package arrives, you can use gloves to handle it or wash hands immediately after, and also let it sit for a few days before opening. If you are getting deliveries of food, wash your hands after handling those bags or boxes.

Yes. Coronavirus can be expelled in small droplets that are produced when someone coughs, sneezes, talks or breathes. The risk of transmission is highest though for very close contact (less than 3 feet) but we recommend a distance of 6 feet or 2 arms lengths. There is some evidence from recent studies that virus could remain suspended in the air in droplets for up to three hours. This is another good reason to stay home as much as possible.

As of yet, we are unsure of the nature of human immunity to Coronavirus. A recently published study in monkeys has demonstrated that they produce antibodies to the virus, that protected them from a second infection a month later. Over the coming weeks, researches will be studying the antibody levels in the blood of people who have had COVID-19 to understand how strong their immunity is and how long it lasts. If the Coronavirus is like flu, we should expect to have some protection that will last months, until the strains circulating change substantially.

This is the question everyone is asking. The important thing to remember with the guidelines you’re receiving is that they are a direct response to what the virus is doing. To paraphrase Dr. Anthony Fauci’s (head of the National Institutes of Health) recent comments, the virus makes the timeline, not us. We are monitoring the numbers of cases and deaths and constantly updating the guidelines you’re receiving. Today, March 26, the US just passed 1,000 COVID-19 deaths and we know this definitely won’t be over in a few weeks. We need to continue to have these important interventions in place for a while.

Without these interventions, we would be facing more cases and even more deaths. We need to continue to slow transmission. Returning to high contact lifestyles too soon would lead to a rapid increase in new cases and create an even bigger outbreak than what we’re facing right now. It would lead to a new shutdown that will be more extensive and last longer. Letting up too soon will be a waste of all the hard work you’ve already done staying home and upending your lives.

Scientists and doctors need this time to build knowledge on this new virus. We need to increase testing ability, prepare hospitals to provide treatment and care for a lot of patients, and design drugs and vaccines. In the next few weeks, we are not going to go back to the way things were, but we will find a new normal. We will see continuously updated interventions through the summer and a reassessment in the Fall, and it’s really important that we prevent a large resurgence then.

During this time, we all want to snuggle with our pets but we want to make sure that it’s safe for us and safe for them. At this time, the CDC reports that there is no evidence that animals play a significant role in spreading the virus that causes COVID-19. We are aware of a small number of pets, including cats and dogs, that have been infected with the virus that causes COVID-19, mostly after close contact with people who had active cases of COVID-19. This means you should treat pets as you would any other family members: Like the rest of the members of your household, you should keep your pets in the house and not transfer them between households. And if someone becomes sick, isolate them from the human and non-human members of the house.

We also know the virus can survive on surfaces and objects, and transmit between people that way. It is technically possible that the virus could survive ON a pet for a short while. There’s no evidence that the virus has ever transmitted between people this way, but to be safe, frequent handwashing and avoiding touching your face will be protective.

If you have a household member with a suspected or confirmed case, act as if it has been confirmed and as if everyone else in the household is infected. Isolate the sick family member. Give them a room that they don’t have to leave, where they can rest. Leave their food by the door, and whatever else they need. Eliminate or reduce the objects coming out of their room and treat those objects as if they are carrying live virus. If you have two bathrooms in the home, use one specifically for the sick individual. Have them monitor and record their symptoms as long as they can, especially their fever. If things worsen or if another household member develops symptoms, contact a health care provider over the phone or online. Since the entire household will have been exposed, everyone needs to stay inside. Have necessary items delivered or make do with what you have in your home. Call your neighbors and lean on your community. And neighbors help each other. It is safe to drop off bags of groceries in front of your neighbor’s house.

If you’re unwell or if you have any reason to suspect you may have been exposed, even if you feel fine, don't go out. Don't’ go anywhere. Stay home, monitor your symptoms, and isolate yourself. Have a friend, neighbor, or delivery service drop off necessities in front of your door.

If you have had no suspected exposure to the virus and you have no symptoms, you can go shopping yourself. Limit the number of trips you make, so buy enough for a week or two. Be very deliberate and surgical about it: Make a list, go the store, get what you need, come home, and wash your hands. Use the self-checkout if you can. Wash your hands and don't touch your face.

Yes. A number of countries are currently rolling out antibody tests and the phrase ‘immunity passports’ is being used to describe how with a positive antibody test people may be free to go back to work. In the last few days the FDA approved a rapid antibody test that can be used by diagnostic labs to determine in just 2 minutes if someone has antibodies in their blood. As an important note, it can take several weeks to make strong antibodies. Once these tests are broadly available people will need to wait for several weeks after getting sick so that their results are accurate. These tests will initially be carried out on people who tested positive with a COVID-19 diagnostic test to make sure the antibody tests are accurate.

The novel Coronavirus is a small sphere with protein spikes on it that allow it to attach to our cells. Below that is an oily layer that coats the virus. When you use detergents like soap or alcohol you disrupt that oily layer and the virus degrades. We also know that on average people touch their faces 23 times an hour! So washing your hands with soap or an alcohol based product will help prevent transmission through that route of infection. It doesn’t mean that you can’t get the virus by other means like inhaling it in droplets or aerosols. We do know from a study done in Hong Kong in the Fall after the SARS outbreak that when the population was being very vigilant with their hygiene that the regular cases of annual flu were substantially reduced. While these data are not specific for Coronavirus they do show that handwashing can reduce the transmission of respiratory transmitted viruses.

First this is a new virus. That means our bodies have not seen this virus before and we are unlikely to have any antibodies. This virus seems to be spreading through the human population much faster than flu, and part of that has to do with the fact that all of us are susceptible. With the flu, most of us are carrying some level of antibody protection from a previous year’s exposure or from a vaccine. Additionally, the case fatality rate is estimated to be 10 times higher for COVID-19 that the flu. Lastly, this virus is new to medical personnel, too. They are learning how best to both take care of patients and possibly treat it.

Given that the novel Coronavirus is a respiratory transmitted virus, we expect that at some point there will be season patterns of transmission, rising in frequency in the colder months just like flu. Because the virus is just sweeping through populations however and people are highly susceptible it may not behave in this predictable manner initially. Additionally, we will first need to see how the virus spreads through the summer months. That pattern will be dependent on a range of factors including transmission in warmer/humid weather, the degree of immunity in the population and our level of physical distancing.

There are no known or approved effective treatments for COVID-19. Recently, the World Health Organization launched a set of multi country global trials on 4 sets of drugs to compare the severity of disease and survival of people on the drugs vs those not. One drug that has been controversial, chloroquine, has been included in these studies. The scientific community is urging caution as the original study showing potential efficacy of chloroquine + an antibiotic was based on a very few number of patients. Many of those patients were lost out of the study into the ICU, meaning they did indeed end up having severe disease, a fact not captured in the data. The FDA has not approved the use of chloroquine for COVID-19. In the coming weeks, the WHO led global studies should provide some information about treatment options. In the meantime, people taking chloroquine without evidence of efficacy are putting themselves at risk of side effects and limiting the ability for patients who take the drug for other conditions like lupus from accessing it.

As long as you’re feeling healthy and don’t think you’ve been exposed to the virus, going for a walk is an excellent idea. Fresh air and a change of scenery will lift your spirits. However, the rules of physical distancing still apply. Don’t get close to people and maintain your six feet of separation. We’re seeing some cases where people are advised to go out to parks and then the parks become crowded and have to close. So go outside but only if you can maintain responsible distance from others.

In addition to soap and water, alcohol is a recommended cleaning agent to destroy the coronavirus.

Beth told you in a previous video that soap inactivates the coronavirus by destroying the lipid, or fatty, bilayer that holds the virus together. When a virus’ proteins, lipids and RNA fall apart, the components are no longer viable and virus becomes inactive.

That’s how alcohol works, too. When you soak a virus in alcohol – in this case ethanol or isopropanol – and let it air dry, the alcohol breaks down the fatty bilayer that holds the virus together.

Specifically, you’ll find 70% alcohol easily available. Anything between 60-80% alcohol will work just fine. People will sometimes assume that if 70% alcohol is good at destroying viruses, then 90% must be better. This is NOT true. Anything over 80% alcohol will evaporate quickly and may not have enough time to destroy the lipid membrane sufficiently.

Similarly, alcohol that is weaker than 60% will not destroy the virus’s lipid layer, it has too much water in it. This also means you shouldn’t try to use alcohol that is meant for consumption – a standard bottle of vodka is 80 proof, which means it’s only 40% alcohol and will not effectively destroy the virus.

Essential oils also have a limited effective time of action, due to their volatile nature. So while essential oils like tea tree oil are known for having anti-microbial, non-bleaching properties, these anti-microbial properties are significantly weaker than synthetic compounds.

To destroy the coronavirus, soap is most effective at breaking down the fat layer, and 60-80% alcohol cleaners are also highly effective.

You’ve all heard that the process involves collecting a sample using a nasal swab. But what happens after that? A thin swab is inserted into a patient’s nasal passage for a few seconds. It absorbs the secretions from the surrounding tissue. We use that swab to look for the virus’s genetic material. While our genetic material is stored as DNA, this virus RNA. To look for viral RNA in the sample, we first remove everything else from the sample. Proteins and fats are chemically destroyed so you’re left with only RNA. That includes RNA from the host, maybe the coronavirus, and maybe other viruses. The standard CDC and WHO tests use a process called reverse transcriptase polymerase chain reaction, or RT-PCR. The first step is reverse transcription, where the RNA is used to produce DNA. Then you add a fragment of DNA that is complimentary to a target segment of DNA for the virus. If the virus is present, the fragments will bind to the target portion of the viral DNA. The exact target varies between tests, but process is the same.

Then the DNA is amplified through a polymerase chain reaction, or PCR, which cycles through temperatures that trigger chemical reactions that copy the viral DNA. The DNA doubles in quantity with every cycle so if you started with any, you may have billions of copies of it by the end of just 35 cycles. At the end of this amplification stage, you measure how much DNA is in the sample. A negative result means there was no detectable DNA found at the end of the thermocycles. A positive result means the targeted DNA was detected.

But remember, no test is perfect. False negative results can occur if the sample is collected or transported incorrectly. They can also occur if the patient simply isn’t shedding a lot of virus at the time of sample collection. False positives can occur from sample contamination or by targeting non-unique segments of DNA, which results in the replication of a similar virus but not the target virus. Standardized kits are designed to reduce this error.

After a patient recovers and clears the virus, they will no longer have viral RNA in their nasal secretions and an RTPCR test will come back negative. These tests measure active infections only.

Antibody testing tells us how many people were previously infected with a pathogen. Beth gave us a great overview on this in an earlier video and what it might mean for individuals as we look ahead. Antibodies can be detected during infection or afterwards, even if the infection was asymptomatic and the patient never sought testing or treatment while they were infected.

An advantage of these tests is that they can tell us what’s happening at a population level – for example, what proportion of the population has likely been infected and what proportion is susceptible? Using large numbers of individuals helps overcome the errors of overinterpreting any single test result and the information can help us make public health decisions.

First, serological testing can help us understand the case fatality rate. In a previous video, I explained that the case fatality rate is the number of infections that result in death. I explained we couldn’t accurately calculate that at the moment because we don’t know how many infections there have been and we’re mostly counting severe and symptomatic cases, which tends to overestimate case fatality rates. Serological testing would help us understand the total number of previous cases better than we do now, so we can more accurately calculate the proportion that resulted in fatalities. This same information could help us estimate transmission rates across populations. Which ties in to my next point: Second, serological testing could help us measure exactly how effective behavioral interventions have been. By measuring the differences in serological findings across populations, we can assess behavioral interventions were effective and successful, and try to understand why others might have been less effective. We can use that information to update and adapt the next phase of behavioral interventions.

hile there is a lot of talk about assessing individual immunity to allow the recovered members of society take on critical tasks, we’re not quite there yet with testing accuracy.

The sensitivity of a test describes its ability to correctly identify someone who has had the disease and the specificity refers to a tests ability to correctly identify someone who has NOT had the disease. A false negative from a test with low sensitivity would be misleading, but a false positive from a test with low specificity could cost many lives. This could happen due to cross reactivity with other viruses, which is particularly important because we know other coronaviruses frequently circulate through our populations.

Ideally we would like the sensitivity and specificity of the serological tests to be near 99%, which means that tests should return only about 1 false positive and 1 false negative for every 100 true positive and true negative results.

If we know a test has a specificity of 85%, for example, we can estimate a range of immunity for a population across thousands of samples. That can tell us how many cases to prepare for in the coming months and when to ease restrictions. However, we can’t use a test with 85% specificity to clear a single individual for high risk activities without endangering a lot of lives. The currently available tests need improvement in both sensitivity and specificity before we can use them confidently to assess individual infections.

So while serological tests may not yet be accurate enough for us to make decisions about individuals, they can tell us a lot of important information about populations and making population level health policy.

Every time you go out to get household necessities, you’re taking on some risk of exposing yourself to the virus or possibly transmitting it to others, if you’re infected and don’t know it. And we all know you have to spend money to buy stuff. In a time of physical distancing and not touching objects other people have just touched, what’s the best way to pay? So handing over a credit card and then getting it back is not ideal. The virus survives reasonably well on plastic and rapid exchanges, like credit card handoffs, are particularly risky. Cash isn’t much better, the rapid exchange means the more rapid decay rate of the virus on paper isn’t really a factor.

Your best options are swiping your credit card yourself and never handing it off or mobile payment with a smartphone where again, you don’t hand anything over and you don’t take anything back. When possible, I prefer to use the self checkout, which protects a potential cashier from me and protects me from them.

It is possible to spread the coronavirus with your shoes. If you’re walking in a common area, particularly indoors, there’s a chance someone sneezed or coughed and gravity sent their respiratory droplets to the floor. If the flooring material is tile, stone, vinyl, or another nonporous material, the virus may survive on it. If you walk through it, you could pick it up on your shoe. If those public floors are cleaned well, the risk is significantly reduced. Proper cleaning means using correctly diluted bleach and letting it sit on the surface for ten minutes before wiping it off. If that wasn’t done, this is still an easily managed problem. When you get home, take your shoes off just inside the door and leave them there. Don’t risk dragging the virus into your house and onto your own floors, especially if you have kids or pets, who might pick it up while crawling or zooming. Stuck to the bottom of your shoe with nowhere to go, the virus will dry out and no longer be viable.

You’ve probably heard that a few tigers and other big cats at the Bronx Zoo developed COVID-19-like symptoms. One was tested and was found to be positive. The others are also presumed infected with SARS-COV-2. An asymptomatically infected zookeeper likely unknowingly transmitted the infection. We don't know whether that person transmitted the virus to each of the infected big cats or if that zookeper transmitted the virus to just to one animal, and then the cats infected each other. The animals are all expected to recover. If now you’re worried about your pets, remember, tigers are not very closely related to domestic animals, even your housecats. There’s still no evidence that house pets can transmit the virus to humans. Of course, if you have COVID-19 or suspect you may have it, avoid contact with people and your pet. In that case, your pet could possibly aid in virus transmission to other household members as a fomite, the same way a doorknob could.

During an epidemic, you’ll hear epidemiologists talk about the Case Fatality Rate. The Case Fatality Rate is the proportion of total cases that results in fatalities. This is a population level measurement. With this coronavirus pandemic, we know there are asymptomatic cases, which aren’t diagnosed, as well as symptomatic cases that aren’t diagnosed due to a lack of testing. This means that our records are incomplete for both the denominator – which is the total number of cases – and the numerator- which is the total number of COVID deaths. These numbers are currently skewed towards identifying symptomatic cases and, severe cases, which are more likely to have negative outcomes. Model estimates have tried to account for those biases. For this pandemic, it’s not terribly important for everyone to know a precise number for the case fatality rate, it is more important to realize that even a low case fatality rate in a fully susceptible population like ours, will cause a lot of deaths. You can help reduce these numbers by continuing to reduce transmission. Follow your local current guidelines on physical distancing to minimize the total number of cases – stay home, and stay six feet away from people when you need to go out.

How do we share outdoor space responsibly? If you’re walking, running, or biking side by side with someone, follow the usual rules: six feet of distance.

If you’re behind someone who is walking, running, or biking, the guidelines are a little different. A preliminary study by aerodynamicists using simulations of microdroplets in saliva left behind by a walker, runner, and cyclist shows that your best bet is to stay out of the slipstream, also know as their draft. In other words, to minimize your risk of exposure to viral particles from an athlete ahead of you, avoid drafting. Drafting involves placing yourself directly behind someone to reduce wind resistance. If you’ve been intentionally drafting to gain a competitive advantage, you should stop for now. The study says that to avoid the slipstream of someone directly in front of you, you need to keep a distance of about 5 yards between you and someone walking ahead of you, about 10 yards between you and someone running ahead of you, and a staggering 20 yards between you and someone cycling ahead of you.

If you don’t have quite that much space, you can drastically reduce your risk of exposure by staggering your position, or following someone diagonally instead of being directly behind them. So if a runner or cyclist passes you, offset your position so you’re diagonally behind them, not directly behind them, and keep your six feet of distance the whole time. And if you’re going to pass someone, position yourself diagonally behind them with plenty of distance to spare. So as you approach them, you’re not in their draft.

To figure out where we are in the progress of an epidemic while it’s happening, epidemiologists plot the number of new cases per day, which is called the epidemic curve. You’ve been seeing these plots for coronavirus at national levels, for your state, your county, and maybe your town. During the period when the number of new cases per day is increasing, we are in a time before the peak of the epidemic. When the number of new cases per day begins to consistently decrease, we assess that we might be past the peak. It’s not really possible to define the true peak until after the epidemic is over. Even after cases have started to decline, there’s always a chance that they could rise again if control measure are lifted too early. For this particular virus, we know there are lags in reporting and an incubation period, so the cases reported today represent infections that were acquired sometime in the past two weeks. Additionally, if we see the cases start to drop and people become complacent with their physical distancing, there’s a good chance we’ll see a large resurgence in cases, which could surpass the first wave of cases. It’s important for epidemiologists and policymakers to keep an eye on these epidemic curves to assess the interventions put in place and update them as frequently as necessary. So the peak of an epidemic curve is the day with the most cases per day.

As we look ahead to understanding the long term health effects in people following recovery from COVID-19, we can really only go back as far as the earliest human infections – which happened around December of 2019. We don’t know what this infection means for long term recovery with regards to tissue damage, from mild to severe cases. We know that recovery from any serious illness or stay in intensive care can be difficult. Make sure you follow guidelines for physical and emotional recovery and don't expect recovering individuals to bounce right back.

The other important unknown about long term effects following infection have to do with immunity. How long does immunity last and how strong is it? Scientists have detected antibodies in experimental animals that have recovered from the virus. Moving forward to understanding what that means for humans, we’ll have to test for antibodies, which Beth described in a previous AskCIDD video.

As summer approaches, people are asking about the safety of pools, oceans, and lakes. There are two parts to this answer. First, the virus is not transmitted through water, whether it’s chlorinated water, fresh water, or salt water. So water itself is not risky. Second, we know the virus is transmitted between people and aggregations of people are particularly risky. So the safety of pools and beaches depends entirely on crowds. Crowds at the pool, ocean, or lake are NOT safe and will help spread the virus. Beaches where you can’t maintain at least six feet of space are also risky. And locker rooms at the pool or the beach are very risky because the virus may survive for a long time in those locations. If your household has a pool that no one else uses, that would be a safe option. If you can get directly from your house to a beach where you probably won’t see anyone else, that’s also a safe option. But community pools, crowded beaches, and shared locker room spaces are risky and should be avoided. Unfortunately, for most of us, that means we’ll have to get our beach fix and pool vibes from pictures and memories for now.

When someone gets infected, how long does it take for them to become infectious? There are two parts to this.

First: The time from infection to symptoms is called the incubation period. Using large data sets from China, a few studies have estimated this time to be about 5.1 or 5.2 days for people who became symptomatic. Recall that some people never become symptomatic, so as with anything, there is a significant amount of individual variation around these numbers, but for simplicity, let’s move forward with the mean values.

For this novel coronavirus, scientists used data from China to estimate that 44% of secondary cases were infected during the presymptomatic phase of primary infection. This tells us that the Latent period is shorter than incubation period for this virus. This study inferred that infectiousness started around 2.3 days before symptom onset and peaked at 0.7 days before symptom onset.

Second: the time from infection to becoming infectious is called the latent period.

If we combine what we learned about the incubation period and asymptomatic transmission from these studies, that would suggest that the latent period, or the amount of time until an infected person becomes infectious is about 3 days.


Early Transmission Dynamics in Wuhan, China, of Novel Coronavirus–Infected Pneumonia

The Incubation Period of Coronavirus Disease 2019 (COVID-19) From Publicly Reported Confirmed Cases: Estimation and Application

Temporal dynamics in viral shedding and transmissibility of COVID-19

Some people are worried about the risks associated with ordering takeout. The virus is not transmitted through foods, it’s not a food-borne pathogen like the viruses and bacteria that cause what we often refer to as “food poisoning”. This means that uncooked or cold foods, like salad or sushi, do not pose any additional risk of coronavirus exposure. In general, food prepared in a restaurant kitchen that meets health and safety standards, and there remains open, will be safe. Anything that comes out of a kitchen, including the boxes your food is actually in, should not pose a risk of virus exposure or transmission. The onset of the coronavirus pandemic further prompted additional health and safety measures and chefs and kitchen staff have been wearing masks to prevent the spread of the virus from unknowing asymptomatic infections. The items you should take precautions with include any external packaging that your takeout order may come in. Those bags pass through many hands after they leave the kitchen. For example, if you get your takeout boxes in a plastic bag, toss the bag, wash your hands, and then get into your food. You should also be taking precautions during handoffs, which means delivery or pickups. Any time you’re interacting with someone outside of your household, just keep a safe six foot distance. By taking just a few precautions, you can safely order takeout, help your local restaurants, and enjoy your favorite foods.

We should all be wearing masks when we leave our houses, but are gloves also a necessary precaution for day to day activities? Gloves themselves do not kill the virus. If you’re wearing gloves and you touch something that has virus on it, it can transfer to your gloves. If you then touch your face, you’re just using your gloves to transfer the virus from a source to your face. You can make that mistake with or without gloves on. In some cases, wearing gloves give people a false sense of security, or a sense that they can safely touch things with reduced risk. That will increase a person’s exposure, and in that case gloves are not a good choice. It is more effective to wash your hands frequently and not touch your face than it is to wear gloves and become careless. Wearing gloves does not automatically increase caution or awareness, especially when once the wearer becomes accustomed to them. Gloves are only as effective as handwashing if they’re used properly and disposed of or washed properly. So it’s not necessary for everyone to wear gloves for routine activities.

Some areas are starting to ease restrictions on movement and gatherings. Some businesses will start to reopen. That does NOT mean it’s safe for you to return to your life, as it was before this pandemic disruption. Because it definitely is not. The goal of restricting movement and interactions was to “flatten the curve”. Which meant we wanted to have fewer new cases per day so that our health care systems weren’t overwhelmed. The idea was to use that time to improve our ability to manage this virus. We needed to increase our capacity to test, isolate the infectious and trace their contacts, care for the symptomatic, and quarantine the exposed. If we take the first step in that process, which is testing, for the past week, we’ve been testing about 248,000 people per day in the US. Estimates on how many people we need to be able to test per day range from 900,000 to 4 million. These are absolute minimums for preparedness for the first step in a multi-step management and mitigation process. We’re well behind on where we need to be to meet our testing needs. In Pennsylvania, we’re testing fewer than 6,000 people per day and our target should be closer to ten times that - about 60,000 people per day. So while restrictions may be changing in your area, pay careful attention to what the new restrictions permit. In many cases, these don’t allow for significant increases in activities that would lead to close contact or large aggregations. Most recommendations specify maintaining physical distance outside of the household and continuing to work remotely. Finally, many areas that are reopening and allowing for aggregations and close contacts are doing so prematurely. The risk has not passed and our capacity has not improved enough. To avoid putting yourself and your household members at risk, I encourage everyone to maintain physical distancing practices as much as possible.

Pooled sample testing is an efficient and widely used strategy to test for an infectious disease in a large number of samples. Pooling samples means testing facilities combine a small amount of a sample from many samples, combine them, and then run the test to look for the virus across that combined, or pooled, sample. If a pooled sample tests positive, then sub-pools or individual samples are tested to identify the positive individual samples. If a pooled test returns a negative result, then all individual samples in that pool are negative. This is known as ‘Dorfman testing’ and it is the most widely used form of pooled testing. This strategy is particularly effective if prevalence and transmission of the disease are low in the population.

Pooled sample testing allows testing facilities to process large numbers of samples rapidly. The are three big advantages of this approach:

  • First more samples can be processed in a short amount of time
  • Second, this strategy reduces the total number of tests that need to be done
  • Third, pooling samples reduces use of limited reagents, which are difficult to source when demand is high, like it is right now.

A study from Germany showed that pooling anywhere from 4 to 30 samples was an efficient strategy to detect SARS-Coronavirus-2 without sacrificing test sensitivity. This means they didn’t miss any positive samples in these pooled tests. Each testing facility can determine the optimal number of samples they should pool based on the sensitivity of their tests.

Pooling samples to efficiently and effectively screen a high volume of clinical samples for infectious diseases has been done for a long time. A return to basic operations for most counties and states will require a massive amount of testing because we’ll need to test asymptomatic individuals in addition to symptomatic individuals. Saving costs and time per individual test could help strategic efforts to ramp up testing.

Pooling samples could accelerate new coronavirus testing

Pooling of samples for testing for SARS-CoV-2 in asymptomatic people

Pooled testing procedures for screening high volume clinical specimens in heterogeneous populations

The universal masking recommendation says that all Pennsylvanians should wear a mask anytime they need to leave their homes. Masks are good for two things: protecting other people from your respiratory droplets and protecting you from others’ respiratory droplets. If you’re going outdoors and you’re not going to see another person, even from a distance, while you’re out walking your dog, you don’t need a mask. If there’s even a chance you might see another person, bring your mask with you so that if you see someone in the distance, you have plenty of time to put it on before you’re near them.

While counties are shifting from the red phase to the yellow phase, some people are caught in between, They had been commuting across county lines in pre-pandemic times. There’s technically no ‘legal’ guidelines here but there are three important things to consider.

The first is that the county-level phases are determined by local numbers of COVID-19 cases and estimated transmission levels. At this point, many studies have shown independently that transmission very often happens inside the home. In fact, the household is the most common place for transmission of this coronavirus. The attack rate is the proportion of people who became infected out of all the people at risk during a period of time. In some areas, the estimated attack rate in households for adults is as high as 28%. So the most responsible way to think about how these phases apply to you is to use the location of your residence to determine your level of restrictions.

Second, businesses in counties that are in the yellow phase must provide teleworking options to employees who can work remotely. Further, any return to work places will require that all employees wear masks and maintain at least six feet of distance from others – with an allowance for more distance if employees are speaking or really projecting their voices, because that can also project respiratory droplets. Keeping a safe distance may require changing the layout of office furniture or altering foot traffic patterns to reinforce personal space, especially in common areas. Physical spaces will also need improved ventilation and disinfection. And whenever possible, workplaces will hold meetings virtually, instead of in-person. So just because a business is allowed to open in the yellow phase, doesn't mean all employees will be or should be back on site.

Third, remember that PA, like most states, is still well below the testing goal, which means we’re testing far fewer people than necessary to test to get ahead of the outbreak. Testing is just the first step to quickly identifying cases and preventing transmission.

So even if you live in a county in the yellow phase, everyone who can should continue to stay at home and avoid going out as much as possible.

Patients with existing respiratory condition are at risk for developing more severe cases of COVID-19. There are a lot of factors that can contribute to respiratory conditions, including genetic factors, behaviors - like smoking, and environmental characteristics, like air quality. A lifetime of inhaling air that is polluted with particular matter or irritating gasses can exacerbate existing respiratory conditions. And, even in healthy people, inhaling particulate matter, nitrogen dioxide, or ozone can damage or irritate airways. This may contribute to the likelihood of infection upon exposure or the severity of disease upon infection.

However, we can’t quantify the direct impact of air pollution on COVID-19. In many areas with high levels of air pollution and large outbreaks of COVID-19, we also see a number of confounding factors, like high population density, which leads to increased transmission between people and larger outbreaks.

In the wake of large-scale coronavirus related shutdowns in manufacturing and movement, we’ve seen noticeable improvements in air quality. As we develop ways to incorporate these activities into our new COVID-resilient communities, it is reasonable to think that efforts to maintain cleaner air will contribute to health improvements in a number of ways.

Right now, universities around the world are discussing how they might return to resident instruction for the fall term and strategies range from carrying on exactly as before to having all instruction occur remotely.

Some people have erroneously said that the average college student, aged 18-23, is at minimal or no risk of COVID-19 infection. This is definitely NOT true. Severe cases, while more likely in older individuals, are found in younger, healthy people as well. Let’s also be aware that many college students, of any age, may have health conditions that make them more vulnerable to severe COVID-19 infection than their peers; universities need to create a safe environment for them, too. Many people also think that students are the only demographic to worry about in a return to university operations. This is also not true. Universities need students but they also need staff, administration, and faculty to function. And many of those employees are in high risk groups. And finally, the community that surrounds and supports the university makes enormous contributions to the day to day functioning of collegiate lives. So universities must also consider the health and safety of the members of those communities. University operations are vast and complex and require many healthy and safe people in many roles to function.

By nature, a college campus a high density environment that brings together people from different locations and perspectives. While doing this creates a rich intellectual environment, it also creates a risk for viral introduction and increased transmission on campus and in the surrounding community. A return to campus represents an increase population movement and local population density. Remember, a return to campus may represent an increase in risk for some and a decrease for others.

Given all of that it IS possible to find a safe way to return to campuses. Universities can benefit from flexibility, creativity, and innovation while building plans and policies from the ground up to find new ways of teaching to take advantage of low-contact formats. But it is critical that prevention, detection, and care are at the forefront of the public health plan. Many students do fall into a young and healthy demographic, which means they may be more likely to experience asymptomatic infections so testing must be frequent and rapid and it must be executed at a capacity that reflects the university’s size. It’s also important to note that behavioral interventions are still going to be our primary tool against this virus, so universities need full cooperation from everyone in social distancing, voluntary testing, contact tracing, and isolation because public health is ultimately sum of private behaviors.

As restrictions begin to ease, one strategy for increasing your socialization but maintaining safety is to choose to socialize with only one other family group. These quarantine ‘pods’ or ‘bubbles’ can still be relatively safe if both households are practicing social distancing. You should keep the size of the bubble small, fewer than 10 people. You can also reduce your risk in your bubble by socializing outdoors, washing your hands frequently, and wearing a mask as talking can lead to lots of expelled virus from infected individuals. If you are eating together, get people to bring their own cutlery and dishware and cool side dishes. Hot food can be served up safely directly from the grill or oven pans with utensils and people should all use hand sanitizer before they eat.

MIS-C is a condition where different body parts can become inflamed, including the heart, lungs, kidneys, brain, skin, eyes, or gastrointestinal organs. MIS-C is occurring in some children that are testing positive for SARS-CoV-2 or have evidence of antibodies from a past infection. The condition results from an over active immune response that ends up causing damage to the body. Symptoms include; fever, abdominal pain, vomiting, diarrhea, neck pain, rash, bloodshot eyes, feeling extra tired. MIS-C is similar to Kawasaki’s disease, also thought to be triggered by viral infection. There are some key differences. Kawasaki’s tends to affect only children under 5 and MIS-C has been found in older children as well. MIS-C is easier to diagnose with the characteristic symptom of very severe abdominal pain. Treatment includes the use of anti-inflammatory drugs commonly used for rheumatoid arthritis, and like for Kawasaki’s the delivery of intravenous immunoglobulins or IVIG. IVIG is actually a dose of antibodies collected from the blood of thousands of donors. Like Kawasaki’s disease, MISC is incredibly rare. As of mid-May there had only been ~100 cases of the syndrome across the USA. We know that most kids have asymptomatic or mild cases of COVID-19. For Kawasaki’s, we know there is a genetic component, with only certain kids with particular genetics, susceptible to this over active immune response. This is also likely to be true for MIS-C. So while, MIS-C is scary for parents, they should be reassuring that the risk is actually very low.

Remdesivir is an antiviral that was first developed to use against Ebola virus. This last week, the first data from a double-blind, randomized, placebo-controlled study for use of Remdesivir against COVID-19 was published in the New England Journal of Medicine. Over 1,000 people testing positive for COVID-19 with lower respiratory symptoms were given either the drug or a placebo and followed to examine their recovery. In a double-blind study like this, the doctors/researchers are also not aware who was given the actual drug to prevent any bias in evaluating patient recovery. The study showed that those given the drug recovered on average after 11 days vs those given the placebo who recovering after 15 days. Severe disease was seen in 21 percent of patients on the drug and 27 percent of patients taking the placebo. Death rates were also slightly lower for those on Remdesivir, 7 percent vs 11 percent for the placebo. This study therefore shows some improvement in severity, death rate and duration of disease for people taking the drug. It is not however an instant cure. Additional studies may yield further information on dosing strategies and use in different types of patients.

Several people have emailed with concern about striking the right balance between proper handwashing and hypochondria or anxiety as we return to work. First it is important to remember that most transmission is via respiratory droplets but we do know that good handwashing practice prevents other viruses like the flu. You should always wash your hands after you have been to the bathroom of course and before you eat. How frequently you wash your hands beyond that depends on your circumstance. If you work at your desk all day, you could start by wiping down your desk and keyboard when you arrive. Then you could sanitize your hands before you leave your desk to protect others and again as you return to protect yourself from any surfaces you touched. The great thing about wearing a mask, is that it not only reduces your transmission to others from respiratory droplets, but also keeps you from touching your own face. If you work in high traffic, high risk areas, you might choose to use hand sanitizer every hour or so, or between clients, etc.

If you need to let a workman into your house, you should both wear masks and keep your distance. You can point them in the direction of the repair rather than following close behind. You can also increase air turnover in your house by opening up the windows. When they leave, you can wipe down any door handles, surfaces they interacted with. Similarly, if you are having a responsible, social distancing party in your backyard with a few people and someone needs to use the bathroom, you can let them use it. However, make sure there is a clear path to the bathroom. Set out paper towels for them to dry their hands with. Ask them to use paper towels when they touch surfaces, like the tap etc. You can also wipe down surfaces after then have finished.

In a previous week, we explained that pooling samples is an efficient way to test a lot of samples at once and it can be particularly effective when prevalence is low. This strategy allows researchers to rapidly and cheaply test a lot of samples. In the US, pooled testing is often used in testing for a number of sexually transmitted infections and when screening blood donations for diseases.

So are people actually doing this during the current COVID-19 pandemic? Yes and no. Pooling samples helped diagnostic labs in Wuhan, China rapidly scale up the number of tests they could process per day.

For COVID-19 diagnostic testing in the US, all protocols or changes to protocols must be approved by the FDA. Pooling samples is a change to the standard protocol. Some labs and some tests are approved for pooled testing under an emergency use authorization. So the technical answer is yes, in the US testing pooled samples has begun in a few provisional labs but it’s not yet being done widely.

CDC guidelines for allowing COVID-19 patients to be considered recovered and no longer infectious can include two consecutive negative diagnostic tests. There have been some accounts of individuals who were infected and presented with symptoms, cleared their symptoms tested negative twice, and returned to work. They later tested positive for a second time, sometimes with symptoms. Were these people actually re-infected?

The truth is we don’t really know. It is not typical for respiratory viruses or other coronaviruses to confer no immunity. There are a few possibilities. First, these tests may be erroneous. It’s possible that some individuals are getting false negative results, meaning they never really cleared the virus. They may have been shedding virus below detectable levels when they tested negative. This seems unlikely because many people must receive two consecutive negative tests before they can return to work but it’s possible. Second, this may be due to a different kind of testing error. Some patients may be receiving false positives after fully recovering. In this case, the tests may be picking up nonviable fragments of the virus’s genetic material that remain in the patient’s mucosal members after an infection. Those viral fragments aren’t capable of causing new infections. However, they wouldn’t produce a second round of symptoms in a patient. Third, it is possible that people are in fact becoming re-infected rather quickly after recovering from infection. One instance where positive tests have been documented following recovery is on naval ships, where sailors are in very close quarters and may result in high levels of re-exposure. While not impossible, this is counter to much of what we think we understand about respiratory viruses and coronaviruses. It would be surprising and unexpected if infection confers virtually no immunity for some individuals.

A few different studies have shown that humans who recover from COVID-19 show a significant antibody response up to 14 days after recovery, with no indications of a rapid decline in immunity. Non-human primates who recover from experimental infections with SARS-CoV-2 do not get re-infected when they are challenged with the virus a second time. If some people are actually getting re-infected, is there something special about them or their environment? We don’t definitively know what is happening with people who test positive and develop symptoms after recovering from SARS-CoV-2 infection. This continues to be an area where we need more information to fully understand what’s happening. The duration of immunity following infection will be a critical piece of information in our attempts to return to social interactions.

Some universities have announced that they believe their students are at low risk for severe cases of COVID-19. They feel that this will allow them to re-open in the fall without presenting a substantial risk to the students. This is incorrect and worrisome for a few reasons. First, not all college students are at low risk for severe clinical cases of COVID-19. Most universities have students of all ages and medical histories, and some will certainly fall into conventionally high risk groups for COVID-19. Second, we are just beginning to see some of severe sequelae of this disease. Some healthy, young adults who present with mild COVID-19 infections recover from the virus only to experience complications from blood clots, including severe, sometimes fatal strokes. While rare, this is occurring in numbers that are highly atypical for these patients’ age and medical history. Third, a university does not function solely with undergraduate students. Graduate students, staff, and instructors all have very high rates of contact with undergraduates. Many of those university personnel are at high risk of severe COVID-19 infections and universities simply can’t function without them.

In order to open safely, universities should consider a wide range of preventative interventions and health care resources. University’s should consider restructuring educational interactions. Any return to instruction will lead to an increase in contacts so schools need to make testing widely available, encourage compliance with contact tracing, and provide extensive support for isolation and quarantine.

After a suspected or confirmed infection, the CDC has formal guidelines establishing when it is safe for someone who has recovered from infection to leave isolation.

If you had symptoms that you think or you know you had COVID-19, you can be around other people and leave your isolation after it’s been at least ten days since your symptoms appeared and you have 3 days with no fever and an improvement in symptoms. If you can get tested, you can exit your isolation after two consecutive negative tests at least 24 hours apart, no fever, and improved symptoms.

If you tested positive for COVID-19 but you did not have any symptoms, you can be with others 10 days after you tested positive or after two consecutive negative tests at least 24 hours apart.

Just because you and your partner or roommate are both infected with the same virus does not mean you should consider interacting during any time when either of you could be infectious. Check back in the with the CDC periodically for updates to these guidelines.