The number of reported cases of COVID-19 caused by the novel coronavirus has now risen globally to 272,000 and to more than 18,000 in the U.S. Worldwide, the number of deaths exceeds 11,000 and deaths in the U.S. amount to 233 people so far. In an effort to stem the tide of the epidemic, the entire state of California is now in lockdown.

After a botched bureaucratic rollout, testing of patients experiencing respiratory illnesses for COVID-19 is expanding in the U.S. We are, nevertheless, still lagging well behind some other countries who are using aggressive testing combined with contact monitoring to flatten the curve of the epidemic. Researchers suspect that for every case identified through contact with the healthcare system, there are as many as five to 10 mild or asymptomatic cases that go undetected by diagnostic tests.

It's time for a widespread rollout of serologic testing to get a better handle on the actual extent of the epidemic. People's immune systems produce antibodies to attack and eliminate pathogens like bacteria and viruses. Each antibody recognizes one antigen, which is basically a target molecule that identifies a specific pathogen. In this case, serologic tests would be designed to detect in patients' blood samples the distinctive antibodies produced in response to exposure to the novel coronavirus. General population screening using serologic tests would yield vital information enabling more judicious forecasts of the epidemic's likely course as well as improved understanding of its virulence.

Importantly, such testing would also enable researchers to better estimate the COVID-19 case-fatality rate or the percentage of infected people who die of the disease. As it is, case-fatality rate estimates range from something not much worse than seasonal flu to catastrophically high rates worse than the 1918 Spanish Flu epidemic. Pinning that rate down would help us more intelligently evaluate the usefulness (or lack thereof) of lockdowns like that in California.

Additionally, the development of such serologic tests is necessary in order to check if potential coronavirus vaccines can stimulate people's immune systems to produce protective antibodies.

It's good news that the Food and Drug Administration (FDA) earlier this week loosened its stifling regulations on developing and deploying both diagnostic and serologic coronavirus tests. The FDA notes that around 80 companies have approached the agency about devising and distributing such tests. For example, the Los Angeles-based diagnostics startup Scanwell has devised an at-home 15-minute antibody test for the coronavirus. Despite looser FDA regulations, the company expects that the agency will approve its test in six to eight weeks. The North Carolina-based point-of-care diagnostics company BioMedomics is also waiting for FDA approval for its 15-minute serologic test for use in hospitals and clinics. It's worth noting that its Chinese sister company has already sold 500,000 of the rapid tests in China and the test is widely available in Europe.

Since most experts believe that reinfection is unlikely, serologic testing would identify people who had recovered from the disease and could now go safely back to work and life beyond quarantine.