Scientists confirmed: Coronavirus is transmitted even before the onset of the first symptoms

(Patria) – In most cases, coronavirus infections are transmitted by people who are infected but have not yet started showing symptoms, scientific research has shown.

An analysis of patient groups in Singapore and Tianjin, China, revealed that two-thirds of patients were infected during the carrier's incubation period, before the first symptoms appeared.

This finding is a major disappointment for experts researching the new virus, as it means that isolating individuals after they start feeling unwell or showing symptoms is not as effective as expected; in other words, it is not enough to curb the epidemic. Therefore, measures such as 'social distancing' are necessary to the greatest extent possible. In addition to enhanced personal hygiene, self-isolation is still considered the most effective preventive measure.

Belgian and Dutch scientists used data from epidemics in Singapore and Tianjin to determine the disease onset interval – the interval from the time of infection of one person to transmission to another. Such data is significant in assessing the speed of disease development and spread.

The interval in Singapore was 5.2 days, and in China 3.95 days.

Scientists are also trying to calculate the proportion of infections spread by individuals who are in the incubation period and have not yet started showing symptoms. However, it is impossible to obtain precise results due to a lack of valid data on who infected whom. Nevertheless, even rough estimates show that most of the virus transmission occurred during the incubation period, before the first symptoms.

The British Guardian writes that this finding confirms the recent statement by Marie Van Kerkhove, head of the emerging diseases and zoonoses unit at the World Health Organization, that infected individuals spread the virus most in the early stages of the illness, including the stage before the first symptoms. A separate study shows something similar – that the virus level decreases after symptoms appear.

Rowland Kao from the University of Edinburgh compared the coronavirus to SARS:

- One of the factors distinguishing the coronavirus pandemic from the SARS epidemic in 2003 is that SARS is contagious only after clinical signs develop, making it relatively easier to control. For the current pandemic, it is suspected that a large number of transmissions from person to person occur before clinical signs.

He emphasizes that isolation plays an important, if not crucial, role, but it must be supplemented by other measures, the Guardian writes.