Answering Your Questions About The Spread Of COVID-19

KCBS Radio is answering your questions about all things coronavirus every weekday at 9:20 am

As we continue to navigate these unprecedented times, KCBS Radio is getting the answers to your questions about the coronavirus pandemic and the issues that have arisen around it. Every morning at 9:20 a.m. Monday-Friday we're doing an "Ask An Expert" segment with a focus on a different aspect of this situation each day.

Today we’re holding a broad conversation about the spread of the disease with Dr. Arthur Reingold, epidemiologist and UC Berkeley professor of public health.

Dr. Reingold, you were here on the very first of these "Ask An Expert" segments we did, and now see what it's turned into. Thanks for coming back with us again. How are you?

I'm always happy to help.

Let's just tackle these. I have a long list today ranging from the specific to broader questions about epidemiology and how we understand all the information that's flowing our way.

First one: my roommate is getting what seems like multiple shipments from Amazon everyday. How should we be handling these when they get to our house? She leaves them untouched at the front door for two days, I tend to wipe them down and open them immediately. What's best?

I think either of those approaches can increase safety. Studies show that this virus doesn't survive on packaging, paper or cardboard for more than a few hours. So I think that if you want to bring it in right away because you're worried about it walking off or need it right away, wiping it down is certainly reasonable. Or you can let it sit there for a day or two. I think either of those approaches can be highly effective.

This one is related but it speaks to the fact that so many households have somebody going out to work and somebody not. How much wiping down of surfaces should roommates be doing when two are working from home and one is still going to work because they're an essential worker? 

I think fundamentally what it means is that the chance of the person who has to be out and about for work could bring the virus home and still be asymptomatic and share the virus. It just means that the things we have told people for some time now need to be followed as closely as possible and clearly, decontaminating surfaces, good hand washing, good respiratory hygiene, these are things people should be pretty familiar with now. But it means in that circumstance you need to be more attentive than you might need to be if you didn't have someone coming in and out of the household all the time.

UC Berkeley is doing a study that includes several cities in the East Bay. The study includes both antibody and virus tests. I think there is a 70% accuracy for the virus test, giving 30% false positive or negative. What are the lower detection limits for these tests and how they are interpreted?

So that's a really complicated set of not just one question but multiple questions. The antibody test is really very much an experimental tool. The hope is that that provides evidence of prior infection and perhaps immunity for some period of time, but many of those tests may not be terribly good. Others require validation.

With regard to the PCR test, the test where you take a swab from the nose or the mouth or the throat, increasingly those tests have better accuracy than in those early estimates. The tests are getting better and better. We do know that there are what we call "false positives" where somebody doesn't really have the virus but has a positive test, but perhaps the bigger concern is that some people who do have the virus have a negative test. That's what we call a "false negative."

I would say that those are important considerations in interpreting test results but I don't think they should be an impediment to using these tests to guide public health action or to use them in research.

This next question I could have written, but I didn't. I keep hearing about sensitivity and specificity and I have trouble keeping the two straight. Do you have a way for me to remember?

Sensitivity basically asks the question, of the people who truly have the disease or the infection, what proportion will have a positive test? And of course we'd like that to be 100% but even for the very best tests it's typically not 100%. And of course you could be truly negative today and then positive tomorrow so even if the test is perfect it doesn't necessarily predict what'll happen to you in a day or two.

Specificity is, of all the people who truly don't have the disease or infection, what proportion will have a negative test? How to keep the two apart, or keep them in your mind - I guess I've been talking about these things so long that for me it's second nature but I don't have a good short hand.

Ok fair enough, we'll all have to study a little harder in our graduate level classes.

There is a great deal of talk now about a second wave. What are the circumstances of a second wave? The triggers? Likely locations?

So the concept of a second wave largely comes from the flu pandemic of 1918, when a novel influenza virus - it's a different virus to be sure - first struck in the spring of 1918 and caused a wave of illness and death. And then it went away for the summer as influenza viruses typically do, and then the following fall and winter there was an enormous second wave, much much bigger than that first wave the prior spring.

So people are concerned that even if there's some seasonal reduction because of warmer temperatures, even if we do a good job of sheltering in place and social distancing and the like, that if we see a dimunition in cases this summer, then we could easily see a much bigger second wave of cases in the fall and the winter. Because first of all, we think the virus will still be circulating. And secondly, most people in the population will still be fully susceptible until we have a vaccine to give people.

How and when did the 1918 "Spanish Flu" pandemic end? Is that virus gone or is it still a threat to humans? What are the implications for our current pandemic?

So the 1918/1919 flu pandemic which caused a tremendous death toll around the world probably ended as a result of killing a lot of people, and most other people becoming infected and surviving. So it was probably a result of herd immunity, and basically the virus no longer being able to circulate in a population where most people were immune.

The descendants of that influenza virus, if you will, are still with us. But that's because the influenza virus is constantly evolving, changing antigenic material and the like. We certainly don't have the exact same virus circulating now, because the pandemic of 1918.

If somebody is an asymptomatic carrier do they recover and develop antibodies? Do they cease being transmitters or could they be like Typhoid Mary and continue infecting others unwittingly?

So we don't have any evidence that people remain chronically infective with the COVID-19 virus in terms of how "Typhoid Mary," if you will, remained infective with typhoid for decades. And that has to do with that organism living in the gallbladder and being shed in the stool. People can be carriers of typhoid for literally