“We can’t go to that warehouse and get the 100 bottles on the shelf,” says Liise-anne Pirofski, the chief of the infectious-disease department at the Montefiore Medical Center, in New York. So doctors, scientists, blood banks, and government agencies have begun mobilizing to collect, distribute, and study plasma from COVID-19 survivors. The advantage of plasma is that you don’t need to develop a vaccine or treatment from scratch. But in these early days of the pandemic, when the number of recovered and confirmed patients is still relatively small, finding them will take time. The irony is that the bigger the pandemic gets, the easier finding donors will be.

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Prowell, who had been following the prospects of convalescent plasma closely because she is also a doctor at Johns Hopkins University, was overwhelmed—in a good way—by the response to her tweet. She got hundreds of replies from people who offered to donate or knew someone who might. “That’s very powerful, but it’s obviously not the right way to do this at scale,” she told me. “We’re going to have millions of cases.” The family is still looking for a donor who fits all the criteria.

The way to do this at scale is a national network that connects donors, patients, and their doctors. Such an effort began in late February, when Arturo Casadevall, an immunologist at Johns Hopkins, published an op-ed in The Wall Street Journal suggesting the use of convalescent plasma for COVID-19. He started connecting interested doctors, virologists, immunologists, and blood-banking experts, who all came together to launch the National COVID-19 Convalescent Plasma Project.

The movement has gained traction. This week, New York announced that it would be the first state to try convalescent-plasma therapy, and the New York Blood Center, a major blood bank, began collecting plasma from people who have recovered from COVID-19.

For now, this plasma is going to hospitals in New York, which are using it on a case-by-case basis. A spokesperson at Mount Sinai told me that the hospital expects to transfuse its first patient this weekend. Mount Sinai’s call for donors got thousands of responses, which an army of medical students is now sifting through.

A single plasma donation from a COVID-19 survivor could go to multiple patients. Donating plasma is similar to donating whole blood, except the red blood cells are separated out by a machine and returned to the donor. “We can do two to three people from one donor,” says Bruce Sachais, the chief medical officer at the New York Blood Center. But the majority of these interested donors will not be suitable for one reason or another: The criteria, set by the FDA, suggest that donors should have had no symptoms for at least 14 days. They should have had a lab test confirming COVID-19, which is hard to get now and was even harder to get when the donors would have first gotten sick, several weeks ago. And, as with normal blood donation, patients and donors have to be matched by blood type. Prowell, for example, is looking for someone who is A-positive or AB-positive for Papa Doc.