Understanding the Body’s Reaction to the SARS CoV-2 Virus
As of June 1, 2020, the test we will now be offering a better screening test to see if you have been exposed to COVID-19 in the past. Boston Heart Lab is now offering a two-stage diagnostic test. If the first qualitative test is positive (with a 99.81% sensitivity and 100% specificity) is positive then a second test is completed to quantitate the antibody response.
There are a few stages to this process:
When your body first gets exposed to the virus it takes time for the virus to replicate and for the body to mount a response. This is when viral RNA/viral antigen (Ag) increases. This is the best time for the nasal swab test. This is when symptoms may start to develop around day 5 (range 3-14 days). I use the word may because we now know there are people who do not develop any symptoms but can spread the disease unknowingly.
About 7-10 days later the body starts mounting an attack on the virus in the form of antibodies (IgM and IgG). The first antibodies formed are like scouts and survey and start to attack the virus, they are called IgM antibodies. When this occurs, you may still have terrible symptoms, but those who are asymptomatic can still be spreading the disease.
Then our immune system goes into a stage where IgM antibodies and the memory antibodies, IgG, are present. Again, at this point, a person is still considered infectious and may possibly very sick with the disease.
As our body starts to recover it stops making IgM antibodies and only makes IgG antibodies as memory antibodies, to protect us from re-exposure to the virus in the future. However, again with this virus, we do not know what level of antibodies are needed to be immune from re-infection or how long immunity will last.