OPKO Health (OPK 3.28%), which is on the forefront of testing for COVID-19 and the SARS-CoV-2 coronavirus that causes it, is helping New York City get a handle on how the disease has been spreading through the five boroughs. On Friday, the company's BioReference lab testing subsidiary launched a large-scale SARS-CoV-2 antibody screening service for residents of the city, which was hit particularly hard by the pandemic.

In the opening phases of the project, 140,000 of the municipality's residents will be tested in five locations, one in each of its five boroughs. In the next few weeks, other testing sites are to be opened; OPKO Health did not get any more specific.

A coronavirus colony.

Image source: Getty Images.

Antibodies are proteins produced by the immune system when it fights off invaders such as the coronavirus. Tests such as OPKO Health's detect whether an individual possesses the ones that fight COVID-19. Thus, a positive test indicates the person had been infected, and that their immune system had attacked the virus. There is speculation that that people with such antibodies might have developed a degree of immunity to it.

Also, antibody testing helps epidemiologists and others understand more about the spread of the disease and how frequently infections lead to serious cases. "This type of information will be of great value in helping healthcare professionals to analyze the presence and progression of the disease in order to identify at risk populations for possible early intervention," OPKO Health said in its announcement.

The company stressed that the purpose of its test is not to ascertain whether someone currently has COVID-19. Rather it's used to tell if there has been an infection in the past, because, as the CDC notes, antibodies will not show up in the bloodstream until 1 to 3 weeks after a person has been infected. People currently experiencing COVID-19 symptoms should see a physician or seek a viral COVID-19 test.

On Friday, OPKO Health shares closed 7.7% higher, well outpacing the gains of the major equity indexes and many of its fellow healthcare stocks.