The first type of antibody that appears is called immunoglobulin M or IgM, and its levels rise within a few days of infection. But IGM is a normal fighter. To target and destroy a specific virus, the body refines it into another type of antibody, called immunoglobulin G, or IgG, that can recognize that virus.
As IgG levels rise, IgM levels fall; IgG levels peak approximately 28 days after the onset of infection.
There is a third type of antibody, called IgA, that is present in mucosal tissues – such as the lining of the lungs. IgA is considered important for fighting respiratory infections such as influenza, and is also likely to be central in coronavirus infection.
All three of the tests being developed look for antibody levels; Some seek only IgM and IgG, and still others perform only one type of test.
What can these tests tell us? And what can’t they do?
They start with what we can tell. Because antibodies come so late, these tests are not helpful for diagnosing an early infection. “For that they are useless,” Dr. Virol, a virologist at the Icon School of Medicine at Mount Sinai in New York. Florian Kramer said.
The tests are more effective at detecting the presence of antibody responses in a large number of people, not only to determine who is immune, but also to spread the virus widely across populations.
25 to 50 percent of people who become infected may never develop symptoms, and some may only become mildly ill. Others may know that he was ill, but could not undergo a test. Serology testing will help identify these people and help scientists better estimate the virus-caused Kovid-19 mortality.
Dr. a virologist at Columbia University in New York. Angela Rasmussen said, “We don’t currently have a good number for the number of people infected, much less people who were never infected before.” “So to do this type of serial assessments is really important from an epidemiological point of view.”