RUTHFULLY YOURS

New York Gov. Andrew Cuomo has directed hospitals to begin asking new coronavirus patients for their occupation, usual transportation mode and neighborhood. Although New York has been shut down for seven weeks, several thousand people are still testing positive and hundreds are being hospitalized each day.

Last week Mr. Cuomo disclosed some preliminary findings: Twenty-two percent of those who entered the hospital came from a nursing home or assisted living facility. Ninety-six percent had an underlying health condition. Yet only 17% were employed, and only 4% in New York City had been taking public transportation.

“We were thinking that maybe we were going to find a higher percentage of essential employees who were getting sick because they were going to work—that these may be nurses, doctors, transit workers. That’s not the case,” he said. “They’re not working, they’re not traveling, they’re predominantly downstate, predominantly minority, predominantly older.”

More investigation is needed, but the virus may be spreading mostly within multigenerational households or public housing. Collecting more information about infected individuals’ habits would have been especially useful early in the pandemic before most businesses were shut down. This data could reveal patterns that suggest the most likely venues for transmission.

New York Mayor Bill de Blasio said the city will start collecting employment and demographic information as part of its antibody tests to pin down how the virus has spread. Mr. Cuomo this month released final results from a random antibody test of 15,000 people across the state, which raised some questions that need to be further investigated.

For instance, estimated infections are 10 percentage points higher in the Bronx than Manhattan, which is more dense. Latinos were also more than twice as likely to have antibodies than Asians. Low-income folks are more likely to work in jobs interfacing with customers, but other behavioral differences may account for their antibody disparities.

Surprisingly, millennials who are known to crowd bars and clubs were about as likely to carry antibodies as baby boomers. Even more curious, 12% of health-care workers tested positive for antibodies compared to 20% of the general population. This is good news since it suggests that the virus isn’t mainly being spread via the health-care system. Surveying more people through antibody and diagnostic tests could help experts better identify the major transmission vehicles.

Scientists often use such observational studies to identify risk factors for diseases when they can’t do randomized experiments. Regression analysis can help discern the variables that most influence an outcome while controlling for others. While studies can’t control for all confounding variables, they can still show important patterns.

Incorporating such surveys in random population tests could also let states reopen more safely. People could be asked how often each week they take mass transit, dine out, use a gym or visit a salon. Those who test positive could be compared to those who test negative, controlling for other factors.

No study is perfect, but more data would be useful in deciding which businesses can safely reopen, and if there’s a flare-up, which should be restricted. Note to Mr. Cuomo and other Democratic governors: A more surgical coronavirus response could save as many human lives at a much lower economic cost.