UPDATE (11 a.m. PT on June 5) — As state and local COVID-19 restrictions begin to ease, it's still not clear we can safely have normal social interactions again. And as thousands have gathered in protests over the killing of George Floyd, officials worry about a possible spike in coronavirus cases.
Public health experts and infectious disease specialists can help us think through our choices about spending time with others — including Dr. Kim Repp, Washington County’s chief epidemiologist, and Dr. John Townes, professor of medicine and medical director of infection prevention and control at OHSU. They joined OPB’s “Think Out Loud” to answer tough questions about safe social interactions during the coronavirus pandemic. (Townes provided answers to additional questions later via email.)
Will we see an increase in COVID-19 cases following mass protests?
Dr. Kim Repp: It wouldn't be surprising due to the lack of social distance between people, when you get any group of thousands of people together, whether it's a concert or a protest. It increases the likelihood of transmission for people that are close together and are excreting respiratory droplets without a mask, with talking or yelling or chanting. It could increase transmission of COVID — I wouldn't be surprised to see any spike in cases across the country, and world.
What’s the risk of spending time with others outside our home?
Dr. John Townes: One has to consider the risk to yourself, the risk to the other person that you're socializing with and then the risk that interaction has for the general public and for anybody else.
We have to talk about the risk of transmission, but also the risk of severe illness.
If you are a person who is at risk for severe illness, such [as] diabetes, hypertension, other conditions like cancer, or immunocompromised conditions ... having social interactions with others is a bit more hazardous.
Is there data on how different forms of social interactions could spread COVID-19, such as a basketball game, or through a hug?
Repp: It depends on masks. It depends if anyone's sick. It depends on wind. It depends on so many different things. So we don't have data on specific sorts of activities, but we do know [that] the more ... aerobic that kind of activity [is], the more droplets come out.
In the formal definition for the Oregon Health Authority ... if you’re within 6 feet and the person is positive, that’s a pretty high risk exposure if it’s longer than 15 minutes.
What we can tell you right now based on the literature: it’s okay to be with people, if you can keep your distance.
If [Dr. Townes] and I are together, and he’s 10 feet away from me and we’re having a conversation, that is a very, very low risk encounter. If we go play a game of basketball, not only would I lose horribly, but there’s a much higher risk of transmission there if one of us is sick.
Can I visit other people if my kids are in day care?
Townes: These are difficult questions with no real right answer. ... In this kind of situation, one has to balance the risks and benefits of the interaction that you're going to have.
We know that the risk is proportional to the number of contacts that a person has, and the probability of transmission for each of those contacts.
So you evaluate the day care center. ... Are they doing all of the things that they need to do to prevent transmission to those kids? Is the staff trained in hygiene? Are they excluding kids who are sick? Are they cleaning up the area well, are they spacing the kids well or are the kids on top of each other and drooling on each other? How much contact is there?
I think one of the big unknowns here is the infectious dose that is required. We don’t know exactly how much a person has to get exposed to get ill. We also know that children seem to be less likely to develop illness than adults, so there’s something there. It’s inherently a problematic kind of situation when you have large numbers of kids in a room.
You have to balance though, with the risk and the need for the child to develop, for the family to progress and for the people who have a job. All of these risks have to be balanced with the benefits.
Would it be safe to fly to participate in a celebration of life for a family member who has died?
Repp: The problem with COVID is that we know you can not have symptoms and you can still transmit the disease. So even if you feel good, look good — you could still be infected. This has been so difficult, that even when a family member is dying of COVID in the hospital, they have to stay separated, [and] we can't let the family inside with the person. So people have made tremendous sacrifices for their own health and safety.
Personally, I don’t think this is going to be gone by the end of summer, I think we’re just getting warmed up. If you consider the medical fragility of the people that you’re going to visit, I think it would be best to think long and hard: What would be the most appropriate risk to take there?
In New Zealand and other parts of the world, families are officially allowed to create “double bubbles,” combining households to create isolated social germ circles. Could we see that in the United States?
Townes: You would probably need to have very rigorous testing to know that either everyone in the group is immune, or no one in the group is infected and has contact with anyone from outside. You have to consider the prevalence of disease in the community as well — the probability that any one of those people in that group could get ill. ... That may not work in a place like New York City during the peak of their outbreak. In a place like New Zealand, where the overall incidents of infection is extremely low, that might work.
Repp: When we love someone, when we care about them, when we're comfortable with them, we subconsciously move closer to them. Trying to make these bubbles where five or 10 people may agree to not come into contact with anyone else — it's nearly impossible to maintain that with two people. I can't imagine how successful it would be with 10.
Can I visit another person’s home if I interact with coworkers in the workplace?
Townes: The risk of transmission is probably related, not only to the distance that you are, but the ventilation system of where you are.
So if you’re outside, the virus particles that come out of a person’s mouth are probably diluted in the air, and the amount of dose someone might get from another person that’s infected would be lower outside than inside.
If you’re indoors with a person, ideally it’s a big room where the ventilation is good.
How should we be thinking about people whose children attend the same child care? Can you hang out with them in your homes because you’re all exposed to each other anyway?
Townes: While there have been some outbreaks in daycare centers, most SARS-CoV-2 transmission occurs within households where people have prolonged close contact with each other, sometimes in homes with inadequate ventilation and/or hygiene. It is entirely possible that the mother or father or another family member of your child's daycare friend has risk factors for illness other than your child's daycare exposure that exceeds those of anyone in your household. When they visit your house they bring those risk factors with them independently from your child's interactions in daycare.
The CDC has information regarding the prevention of transmission in daycare settings.
Would it be safe for people to have a few regular social interactions?
Repp: I think that we can't stay completely socially isolated forever, but what I do know is, if we start to get an increase [in] cases, [and] we double or triple our case count in a matter of weeks, we're going to have to shut this all back down again. So it's kind of got to be a team effort of everybody doing the best that they can, while balancing the risk and still meeting their social needs in a way that won't risk the health of others.
What about a planned family reunion two months from now?
Townes: Personally, I would not be planning an in-person family reunion for any time in the near future that involves a gathering of people who may be at risk of severe illness. If you're like my family, there would be a lot of hugging, laughing and singing involved, all activities that increase the risk of virus transmission. Since only very few people in Oregon have been infected with this new virus so far, and it is doubtful that we will have a vaccine in the next two months, there is a good chance that nearly all people at the reunion will be susceptible to infection.
It would only take one infected gregarious relative (or ill staff at the venue) to cause an outbreak among your family that they would then take with them on their travels home. And because people can be contagious for a day or two before they have any symptoms (and some who are contagious never have symptoms) it’s hard to predict the risk when large numbers of people gather. Even if the risk is low that any one person in the group is infectious, the risk is additive when people gather.
How about backpacking ... if each household transports themselves to the trailhead separately, cooks and tents separately?
Townes: In general, outdoor activities that don't involve direct contact between people are lower risk than gatherings with people indoors, but maintaining physical distance and limiting close contact with others are important measures you can take to limit transmission. If all members of both groups are living and working in areas where the rates of infection are low (which includes much of Oregon) and have no known exposures to known or suspected cases, then the risk of transmission on this type of outing is very low.
The question is whether all members of each group are willing and able to wear a mask to limit the generation of respiratory aerosols when close to members of the other group, and are able to limit physical contact and sharing of personal items. Another factor to consider is whether anyone in either party is at risk of severe illness, such as adults over age 60, those with hypertension, diabetes, chronic lung disease, cancer, impaired immunity or other chronic health conditions.
It may be a good idea to check with park service officials regarding the place where you will be backpacking to make sure overnight visiting/camping is still allowed or if special rules are being enforced.
What should people be thinking about when they think about dating?
Townes: I assume you mean what sort of COVID-19 prevention measures people should be thinking about? 😃
Don’t be a super-spreader. If you have been infected with SARS-CoV-2 (and you may not know it if you have), the number of people you transmit the virus to is dependent upon: 1) The number of close contacts you have with others while you are infectious. 2) The probability of transmission during each of those contacts. 3) The duration of time you are contagious.
You can control the number of contacts you have — ideally, if you are dating, make an effort to have in-person dates with as few different people as possible. Try having virtual dates for a while before getting together in person with your date. Then, once you have established that they are doing the same and are not otherwise at risk of infection, take it to the next level if you feel comfortable doing so.
You can control the probability of transmission during a date to a certain extent. The probability of transmission for each contact depends on many different factors, such as the duration of contact, physical proximity, ventilation, how much and how loud you talk and laugh, sharing of personal items, exposure to body fluids, and use of barriers to limit such exposures. Meeting someone outside wearing a mask for a short time is going to be a lot less risky than sleeping over. It’s nice outside right now. Have dinner outside or a picnic in the park, preferably one that isn’t crowded.
Until there is an effective therapy, there isn’t anything a person can do to limit the duration of time that they are infectious. Virus genetic material (RNA) is detectable by PCR (polymerase chain reaction) in oral and nasal secretions and fecal material for about three weeks after symptom onset on average (sometimes longer, sometimes shorter) but infectiousness is greatest for a day or two before symptom onset and for at least a week afterward.
What about pets? Is it OK for me to pet a cat I see out on a neighborhood walk?
Townes: It is probably OK to pet a cat you see on a neighborhood walk. The risk of infection in cats in Oregon is almost certainly extremely low, but the prevalence of the disease in cats and the precise risk is of SARS-CoV-2 transmission is unknown. Experiments have been done in which cats have been inoculated with the virus, and it has been demonstrated that they can be infected and pass the virus on to other cats. But transmission does not appear to be very efficient.
The extent to which transmission from humans to cats and from cats to humans occurs under non-experimental conditions is still to be determined, but human to cat transmission appears to be possible. Two tigers in a New York zoo became infected after being exposed to a zoo employee who had COVID-19.
The CDC has some helpful information regarding SARS-CoV-2 in pets and other animals.
Can we get a valid antibody test?
Townes: There are many laboratories that are offering tests that detect antibodies to SARS-CoV-2 antigens, but the performance of these tests is highly variable. Most of these antibody tests suffer from lack of specificity: they may show the presence of an antibody, but it may not be an antibody that is directed specifically at SARS-CoV-2.
In general, the predictive value of a test depends on how likely the person has the disease in the first place. When the probability of SARS-CoV-2 infection is very low, as it is in Oregon, even in a best-case scenario with a test that is 98% specific, widespread testing of asymptomatic people without known exposure is likely to generate more false-positive results than true positives. (For a technical explanation of Bayes’ rule and the predictive value of diagnostic tests in general see: Katz, MA, New England Journal of Medicine, November 21, 1974, pp 1115-6). In addition, we do not fully understand yet which types of antibodies correlate with immunity, at what serum levels, and for how long.
As a result, doing antibody tests in low prevalence areas in persons with low risk of infection may lead to false reassurance of immunity, ultimately resulting in behaviors that may put them at greater risk for infection. Some OHSU researchers are working on developing better antibody tests and studying how they could be deployed. The Infectious Disease Society of America has produced some useful information for clinicians regarding antibody testing. More information about antibody testing can be found here.