Unfortunately, experts generally agree that the actual number of Americans carrying the virus by the end of January was nowhere near high enough to support speculation about herd immunity and star-studded superspreader events. Beyond that, the estimates vary widely. Lauren Gardner, an associate professor of engineering at Johns Hopkins University, who created the school’s popular dashboard for tracking coronavirus cases, told me that “there could have been hundreds of cases in the U.S. in January and thousands by the end of February.” Trevor Bedford, a biologist at the Fred Hutchinson Cancer Research Center who has been at the forefront of the genetic study of SARS-CoV-2, says that “more than 10, less than 100 would be my guess.” Caitlin Rivers, a senior scholar at the Johns Hopkins Center for Health Security, told me that she’s “confident it is not zero” and that “it seems like it’s not millions.”
It is scientifically possible for a country months into an infectious-disease outbreak to determine with some certainty how many of its residents were infected in the first few weeks. The challenge is that doing so would require data about the United States and the rest of the world that are currently a mystery. Many Americans’ most pressing questions—did I have the disease without knowing it? When?—will remain unanswerable forever. But with time, we’re likely to gain some limited clarity about what exactly happened at the beginning of this year. And we’re probably not going to like what we find.