Dear Readers: Fielding Your Thoughts and Questions on Covid-19


As the novel coronavirus pandemic continues to spread, Undark readers have been sending us numerous and often insightful questions, comments, and observations on the subject. We’ve asked the Pulitzer Prize-Winning science journalist and Undark’s publisher, Deborah Blum, to dedicate some time to responding — both as a reader service, and as another way for Undark to cast some light into the darkness of misinformation, rumor, fear, and conjecture now percolating through the information commons.

Additional installments of this Q&A feature can be found here. If you have questions, comments, or would like to see some other aspect of the Covid-19 crisis explored in a subsequent feature, please write to write us at: (Reader questions and comments below have been edited for clarity and brevity.)

Do those people who have had the virus develop an automatic immunity to reinfection? If yes, how long does that immunity last?

At this point, the likelihood of reinfection with SARS-CoV-2 remains uncertain, although the early evidence offers some reassurance. One recent study with laboratory monkeys — published in preprint, which means it has not yet been peer-reviewed — found that animals that were infected with the virus and then later deliberately re-infected did not fall ill again. However, that study involved only four monkeys, so should not be considered definitive.

Infectious disease experts note that immunity after infection may, as with many viruses, depend on the severity of the illness and the strength of the resulting immune response. Other coronaviruses, which cause mild seasonal colds, are known to re-infect after a period of some years. There may be varying levels of immunity, although scientists point out that even immune variation will offer some protection within a community. “That is the hope,” one coronavirus researcher told NPR. But at this time, he added, “there is no way to know that.”

Could the items I purchase from the store carry active coronavirus on the packaging that might infect me? Should I leave the packages outside for an hour or two while I go inside my house and wash-up?

There’s no obvious reason to leave packages outside. If you are ordering food packages to be delivered through the mail or similar services, the current evidence suggests no particular risk. The U.S. Postal Service has issued a statement on this subject which has links to reassuring advisories from public health agencies, reinforced by guidance from experts like Dr. Anthony Fauci, director of the National Institute of Allergy and Infectious Diseases.

In fact, many such experts recommend food delivery over shopping at a grocery store in the interests of social distancing. However, in either case, you can add an extra layer of protection through judicious use of soap and water, or use of a disinfectant. Additional recommendations for those wanting to be extra safe: Wash food containers (such as plastic containers of cottage cheese) from a grocery store. It always makes sense to wash produce as well, and yes, it’s also good practice to wash your hands before handling food — even absent a global pandemic.

I get conflicting information about the viable length of time the virus can infect people. From 20 minutes on a tabletop, to six hours floating on “air motes?” And for that matter: Is the virus airborne or not? And if no — why the protective face masks?

Protective masks, such as N95 respirators, are essential for health professionals in particular. As with most respiratory viruses, SARS-CoV-2 can infect through airborne viral particles — usually emitted by a cough or sneeze — that float briefly in the air and then settle, for longer periods of time, on nearby surfaces.

Estimates have varied but a recent paper, published by a collaboration of government scientists, suggests that the virus can be detected in aerosol form — meaning in tiny floating droplets — for up to three hours. In general, these droplets tend to spread no more than 6 feet from an infected person, which is why the recommendation is to stay 6 feet away from others in order to protect yourself. Once the viral droplets land on a surface, research supported by the National Institutes of Health suggests that the microbe is detectable for up to four hours on copper, 24 hours on cardboard, and two to three days on plastic and stainless steel.

A recent analysis of cruise ships carrying infected passengers also underlined the hardiness of this particular virus, suggesting it could stay on uncleaned surfaces for more than two weeks. The bottom line: We’re still figuring these numbers out. And, this won’t surprise you — the best way to respond if you are worried about touching a surface is to wash your hands afterward, with soap and water, for a good 20 seconds.

Can someone find out more about the number of people infected that show no symptoms?

As with other aspects of the disease, we’re still figuring this one out, too. Scientists began warning early that “silent spreaders” — people infected with the SARS-CoV-2 but as yet showing no disease symptoms — were a major factor in the pandemic’s rapid spread. A study published in Science in mid-March, analyzing data from undiagnosed infections during the original outbreak in Wuhan, China, found that these ended up being the “infection source for 79 percent of documented cases” of illness.

One of the reasons that this turns out to be such an issue, research suggests, is because people can shed the virus at a fairly high rate — even before they are symptomatic themselves. An analysis of infected people in the Lombardy region of Italy — another viral epicenter — found that viral particles in nasal passages were roughly the same in the week before symptoms appeared as after. That study, so far only published in preprint, can be found here.

But what percentage of the infected population is actually asymptomatic and shedding? As mentioned, that remains uncertain, but an analysis of viral spread on the cruise ship Diamond Princess estimated that about 17.9 percent of infections were asymptomatic, while a comparable study of Japanese nationals evacuated from Wuhan set the number at 33 percent. As testing and diagnoses increase, we might hope to see more precise numbers.

I’m not seeing six or more months of a severely truncated life to be a great sacrifice, because it is toward a very positive end. I am overjoyed, because that means we will experience the minimum number of deaths, the minimum number of severe cases, instead of simply extending the period of infection.

What can we possibly say to that? Thanks for sharing this healthy and helpful perspective.

And on that positive note, we’ll close — but again, if questions or observations occur to you as this pandemic moves forward, don’t hesitate to share. We’ll do our best to include your input or otherwise provide you with realistic answers — and we can promise you they’ll be well researched ones. Please email us at


Deborah Blum is the director of the Knight Science Journalism Fellowship Program at MIT and the publisher of Undark.