Projections of imminent COVID-19 diagnoses can be overwhelming. Asked in an interview why the virus is spreading so far and so fast, Dr. Lee Riley, public health professor and chair of Berkeley's Division of Infectious Disease and Vaccinology, says: "We don't really know why this is happening. But one of the observations being made in China, where they have a lot of experiences now, is that the virus seems to be able to transmit even before someone becomes symptomatic. ... And then even after an infected person recovers from the illness, they continue to shed the virus up to two weeks to even 20 days. So there's more opportunity for an infected person to transmit. That's why I think so many other people get infected -- because there's many more days of infectious period for a person to contract the virus. That may be one of the reasons that it's spreading so quickly." Regarding the numbers of confirmed cases and how testing delays and shortages may be affecting them, he says: "One caveat is that these numbers that we're getting may be somewhat delayed because as you know, the testing is increasing in number, and so there's a real backlog of the tests. We don't really know exactly what's happening now. The numbers that we're seeing are based on the tests that were done several days ago, and they're just coming up because [at] a lot of the testing services, there's a huge backlog right now. ... We don't know which direction this is going to go. We may see a continued increase, a huge bump in the next several days, but that just means the results are just coming in."