We still don’t know how many people have been infected with the novel coronavirus, SARS-CoV-2. Not only have countries struggled to roll out wide-scale testing for the virus, those efforts inevitably will miss people who have recovered from an infection.
The best way to figure out how far and wide the virus has spread in a population is to look at blood. Antibodies, blood proteins that the immune system produces to attack pathogens, are viral fingerprints that remain long after infections are cleared. Sensitive tests can detect them even in people who never felt a single symptom of COVID-19.
The World Health Organization has announced an ambitious global effort, called Solidarity II, of so-called serosurveys, studies that look for antibodies to SARS-CoV-2 in the population.
The United States has launched an unprecedented effort as well. One serosurvey is already underway in six metropolitan areas, including New York City, the hardest hit city in the United States. A second, even larger one, is on its heels, and together they should give a strong nationwide effort to track closely how many Americans have become infected as the pandemic unfolds. Serosurveys may also help efforts to develop vaccines, and, separately attempts to devise therapies to stop the virus from causing harm.
Science talked to Michael Busch, a transfusion specialist based at the University of California, San Francisco (UCSF), who is one of the leaders of these efforts. Busch has studied human blood infections caused by every imaginable virus. He directs the Vitalant Research Institute, a nonprofit that’s linked to 170 blood donation centers in the country and is world renowned for its infectious disease studies.
This interview had been edited for length and clarity.