Scientists reveal when patient with COVID-19 is most infectious

A study by Chinese scientists found that in 44 percent of cases, the spread of the new coronavirus occurred through infected people who had not yet begun to show symptoms of COVID-19. Moreover, the peak of infection happened for a period of one to two days before the onset of the disease, Olaylar reports via Nature Medicine.

The results showed that the amount of virus genetic material was highest on the first day of symptoms, and then decreased for about 21 days. Authors say this indicates that the most robust production of the virus by an infected person occurs at the very beginning of the infection, even before the immune system turns on to kill the viruses and cause symptoms.

An analysis of 77 cases where both the source of infection and the infected person were reliably known allowed researchers to calculate when people are most infectious. According to scientists, contagiousness occurs 2.3 days before symptoms appear and peaks 0.7 days before the onset of the disease at the source.

Moreover, scientists note that samples from the nose and throat of patients contained a vast number of viruses-about 1000 times more than in patients with SARS, which partly explains why the new coronavirus is so contagious.

There is also encouraging news. Approximately ten days after the onset of the disease, the number of infectious viruses released by the patient falls sharply, which means that by this time, the antibodies that the bodychr("39")s immune system produces against SARS-CoV-2 kill the replicating viruses. Another conclusion is that people with bright manifestations of COVID-19 secrete more infectious illnesses than asymptomatic carriers.

But there are also not very good results for those who are ill. Scientists have determined that virus discharge from the nose and throat occurs only in the early stages of the disease. At the time when bright symptoms begin to appear, and the release of the virus reaches a peak, the infection often already has time to reach the lungs.

According to the authors of the new study, contact tracking and single case detection may not be effective in stopping new outbreaks. As they estimate that more than 30 percent of cases are due to pre-symptomatic or asymptomatic transmission. We need to identify more than 90 percent of the viruschr("39")s distributors and conduct tests to stop the epidemic.