Boston and Massachusetts General Hospital said Sunday they've begun recruiting 1,000 people in the 02121 and 02125 Zip codes - and in East Boston and Roslindale - for antibody testing that might help show just how widespread the coronavirus is in those communities.

The testing, announced by Mayor Walsh, involves people who have not shown any Covid-19 symptoms being tested to see both if they have an active infection and if they have been exposed in the past:

"Testing for COVID-19 virus is done by means of a swab of the nose and determines if you have the infection. Antibody testing is done by means of blood drawn through a finger prick and detects whether your blood has antibodies that are present when the body is responding to an infection, like COVID-19. Any resident who tests positive for the COVID-19 virus or the COVID-19 antibodies will be provided with clear guidance and information on how to care for themselves and those around them."

Researchers have said large numbers of people infected with the virus never show any symptoms, which has ramifications for determining how to combat it until a vaccine is release, because asymptomatic people can still spread the virus.

Similar testing done by MGH in Chelsea, which has the highest Covid-19 rate in the state, showed that some 30% of residents may have been exposed to the virus.

Accodig to the city:

"Participation in the study is entirely voluntary for residents who have been contacted, is available to them on a first come, first serve basis up to 1,000 residents, and residents will not be charged for testing. Testing for this study is expected to be completed by May 1, and summary data of the the compiled results will be made publicly available, including the numbers and percentage of residents who test positive for the COVID-19 virus and COVID-19 antibodies, both within the neighborhoods included and the total study group tested. In accordance with the Health Insurance Portability and Accountability Act (HIPPA), no personal information from any participants will be shared."

The two Dorchester Zip codes and East Boston currently have some of the highest infection rates in the city, according to figures the Boston Public Health Commission released Thursday: 136.6 cases per 10,000 residents in 02125 and 02121, which also includes part of Roxbury, and 146.6 cases per 10,000 residents in East Boston. Roslindale's rate was 119.9. The neighborhoods with the highest rates were Hyde Park, with 180.3, and Mattapan, with 148.7.

The news comes on the heels of an announcement by the city to begin universal virus testing of everybody who comes into Boston homeless shelters over the next couple of weeks.