Question: I’ve been out in the world the last few weeks mixing and mingling with folks who know folks who are currently under self-quarantine and/or sick or recovering from COVID-19 or the flu (hard to know since testing has been so limited). I’m supposed to go see my 96-year-old mom next weekend, but I’m so scared of being an asymptomatic carrier. What should I do?

Answer: I’m also really concerned about seeing my elders. Again, COVID-19 hits the elderly the hardest — we see increasing severity, including morbidity, associated with increasingly older ages. Obviously, we need to do our utmost to protect this vulnerable population. Since the coronavirus seems to be transmitted most via respiratory droplets, we shouldn’t expect to see much asymptomatic transmission. But that’s an assumption… this virus is new and there’s still so much we just don’t know. As a recent journal article from China states, “The question of “the degree to which presymptomatic or asymptomatic infections can transmit” is not fully understood. There is an urgent need to screen infected carriers in larger close contacts or in the general population, and assess their risk for transmission.” Yet another reason that we need to have widespread testing! CDC does have guidance here that recommends long-term care facilities and nursing homes, “Restrict all visitation except for certain compassionate care situations, such as end of life situations.” Given what we know coupled with what we don’t know, I think it’s better to be overly cautious than not cautious enough. We generally visit my 94-year-old father-in-law every weekend. We’re not going this weekend.

Question: On Thursday, Dr. Acton, the Director of the Ohio Department of Health, said “”We know now, just the fact of community spread, says that at least 1 percent, at the very least, 1 percent of our population is carrying this virus in Ohio today… We have 11.7 million people. So the math is over 100,000. So that just gives you a sense of how this virus spreads and is spreading quickly.” How did Ohio arrive at that estimate?

Answer: Since Thursday, Ohio has backtracked a bit from this estimate, describing it as a “guesstimate.” But we do have modelers working on these very issues. And the models are only as good as the inputs — the data and the modeler’s assumptions. Since we have such limited data in the US right now regarding scope of community spread (blerg! testing challenges have so hampered our response!) I really wouldn’t put much faith on estimates you hear like this. The main thing to keep in mind is that we still haven’t turned the light on, so we just can’t see the full scope of the outbreak in communities across the US. Public health leaders like Dr. Acton are generally seeking to convey the fact that the scope of infections is bigger than we know (tip of the iceberg, so to speak). All that said, here’s a fascinating set of assumptions that modelers are currently using to estimate infections — start with death assumptions. Assume case-fatality rate of 1 percent and that it takes 15 days for an infected person to die, then it means if you have 1 death in Ohio now, you probably had 100 people infected 15 days ago. Now assume that it takes 5 days for cases to double, then over the course of those 15 days, we’d expect to have 800 cases today. Dr. Edmonds from London School of Hygiene and Tropical Medicine gives a good explanation here.