There are a lot of unanswered questions about SARS-CoV-2, and one of them is about the dynamic of the infection. A recent study by Chinese scientists focused on that topic by estimating the number of antibodies (IgM and IgG) and viral RNA in the blood samples of infected people in the time period of 8 weeks.

It was discovered that there were a lot more IgM and IgG compared to S-protein receptor-binding domain (RBD) in the blood samples of people with a low viral RNA load. That concludes the effectiveness of IgM and IgG in the fight with infection and makes them useful in treatments like antibody therapy.

Throat swabs, sputum, stool, and blood samples were collected from 33 patients with confirmed COVID-19. Viral load was measured by reverse transcription PCR. The median time of undetectable viral RNA in throat swab, sputum, and stool 18.5 (13.25-22) days, 22 (18.5-27.5) days, and 17 (11.5-32) days respectively.

The viral load in stool was lower than in throat swab, but was going down slower, sometimes extending the time to 5 weeks. This allows the conclusion that stool analysis might be useful as an extra COVID-19 test to avoid the mistakes by the detector systems.

The other interesting pattern discovered in the study is about the antibodies. The research refutes the idea that IgM antibodies generally appear before IgG, but around 75% of infected patients had the same seroconversion (the time when the antibodies start developing) for IgM and IgG, while 10% of patients had less IgM than IgG during the research period.

It was also found that the IgG load peaked after 30 days from getting the first COVID-19 symptoms. Around 36% had the number of IgG quadruple in the first few weeks of the infection and this group had the viral load getting lower the fastest, which concludes that IgG antibodies can be used in different treatments.

This research makes a good step in learning about the dynamics of COVID-19 and provides us with a few interesting discoveries about potential ways of improving tests and treatments.