Marc Lipsitch writes:

As an infectious disease epidemiologist who has worked on pandemics for two decades, I’ve talked in recent days to journalists and health officials in the United States and from halfway around the world about how to stop the novel coronavirus that causes the disease covid-19. They all have the same questions: How many tests do we need? How should we use tests? For each case we know about, how many more cases are out there? What’s the best way to find undiagnosed cases? Should we do “active case finding,” which involves testing everyone who is mildly ill, then isolating known cases and quarantining and isolating their contacts? Instead — or in addition — should we implement intense social distancing, close schools and take other similar measures?

Everyone asks the same important, interrelated questions. In one respect, the answer is the same for all of them: We must vastly expand our testing capacity. No country has controlled transmission effectively without massive testing capacity. The United States currently has a sliver of the capacity we need, which is a tiny fraction of that available in other countries. South Korea has performed over 320,000 tests — almost one for every 150 people. That is 30 times the testing per capita that we have done in the United States. Exceptional teams are racing to solve testing bottlenecks at local and state levels — Massachusetts is just one example — filling the vacuum left by the complete absence of federal leadership.

Regulatory and technical hurdles accounted for early delays. Now that we’re past those, several shortages are getting in the way. We don’t have enough protective equipment for testers, nor swabs for sampling or reagents to extract genetic material from the virus. We don’t have enough physical test kits, or enough human power to run large-scale testing. The result is that we have no idea how many people are infected with the coronavirus or how fast the virus is spreading. [Continue reading…]