A study in April by the same team showed that 11 percent of Latino participants at another train station tested positive for the virus when P.C.R. was used, compared with 2.6 percent in the city over all.
About 90 percent of people who tested positive in that study were essential workers, and 88 percent made under $55,000 a year, said Jon Jacobo, chair of the health committee for the Latino Task Force. Undocumented community members may also not have access to sick pay or to state and federal benefits, he said.
The task force worked with the researchers to design the study and make it financially possible for those who tested positive to isolate. The organization offered two weeks of groceries to those with positive tests, and a community wellness team delivered other necessities.
Beginning July 1, the city guaranteed two weeks of minimum wage, or $1,285, to anyone who should isolate but could not afford to do so. “The important thing is to always, truly, have a partnership with community,” Mr. Jacobo said.
The project benefited from the researchers’ experience conducting H.I.V. studies in sub-Saharan Africa. “Working in rural areas in Africa is all about talking with the community and asking the question, ‘What works for you?’” said Dr. Diane Havlir, an infectious-disease expert at U.C.S.F. who led the project.
In this case, she said, the community expressed interest in flu vaccination, so the team worked with Walgreens to offer free vaccines at the test site.
Dr. Havlir and other experts acknowledged that BinaxNOW had limitations.
Simple as the test may be, it should be used only by people who are trained to interpret the results, cautioned Jennifer Nuzzo, an epidemiologist the Johns Hopkins Bloomberg School of Public Health.