Via Nate Silver, some more good news on a “good news” sorta day. For weeks now, reports from China and Korea have been floating around that patients who got coronavirus and then recovered later went on to test positive *again,* raising ominous possibilities about what could be happening to them.

Had the virus inside them “reactivated”? If so, it would mean some “recovered” patients aren’t truly recovered and may be walking around infecting scores of other people.

Or had “recovered” patients cleared the virus from their system and then been reinfected?

The entire planet is banking on the assumption that people who beat the disease once won’t be able to contract it again anytime soon. If we can get reinfected then all of our hopes about herd immunity, antibody treatments, and so on are out the window. Even the efficacy of a vaccine would suddenly be in question. How would we ever be rid of a disease that can’t be durably suppressed by the antibodies it elicits in people?

The latest data from Korea is reassuring. People aren’t being reinfected, it seems. What’s being detected in their systems are the mortal remains of a now conquered virus.

“The tests detected the ribonucleic acid of the dead virus,” said Oh, a Seoul National University hospital doctor, at a press conference Thursday held at the National Medical Center.

He went on to explain that in PCR tests, or polymerase chain reaction tests, used for COVID-19 diagnosis, genetic materials of the virus amplify during testing, whether it is from a live virus or just from fragments of dead virus cells that can take months to clear from recovered patients…

“The respiratory epithelial cell has a half-life of up to three months, and RNA virus in the cell can be detected with PCR testing one to two months after the elimination of the cell,” Oh said.

Encouraging, although we’re still left with the mystery of that study from China about low levels of antibodies in some “recovered” patients. Presumably all recovered patients have *some* degree of immunity from reinfection. But they may not have the *same* degree of immunity.

Doctors here in the U.S. are already using antibody-rich convalescent plasma from recovered patients to treat others. Results: So far, so good.

At UW Health, Hartman said five of the 14 patients, all suffering shortness of breath, were treated before reaching the intensive care unit, and wound up never requiring transfer to the ICU.

“There seems to be a sweet spot where patients are early in that disease process,” Hartman said.

Of the nine who were treated while in the ICU, seven have showed signs of improvement, Hartman said, “and two of them didn’t progress as well as we had hoped.”

Those are anecdotal results, not results from a clinical trial, but small trials in China have also looked promising. In one, plasma was given to five patients on ventilators. Four of the five stabilized within three days. In another, 10 patients with “severe” COVID-19 received plasma; symptoms improved or disappeared entirely within one to three days in all 10. For the moment the demand for antibody plasma outstrips the supply since relatively few people have had the disease and recovered, but maybe synthetic antibody drugs can solve that problem. They won’t be ready by tomorrow, but by fall? Maybe?

Speaking of antibodies, a curious piece of data from Andrew Cuomo today:

Does it make any sense that the FDNY and NYPD, especially, would have *lower* incidence of the virus than the general population of the City? Cops can’t shelter in place at home and their job often requires them to be in direct contact with people. If you believe the data that 24.7 percent of all New Yorkers are infected, how can it be that the police force has been infected at a rate less than half of that? Either the number for the City is too high or the number for the NYPD is too low.

Maybe it’s the number for cops that’s too low? I’ll leave you with this, also from Silver — circumstantial evidence that maybe some small degree of herd immunity in New York City’s general population has already been acquired.