One has to inhale an average of 500 corona viruses to become infected with Covid-19.
According to a Viennese researcher, a relatively high number of coronaviruses is necessary to become really infected with Covid-19. The number of inhaled viruses could also determine weak and severe disease progression.
A Covid-19 positive person has been infected with an average of 500 corona viruses, reports Andreas Bergthaler from the Research Center for Molecular Medicine (CeMM) in Vienna. Only this relatively high number of viruses can cause the disease. This is probably why simple measures such as wearing masks and keeping a distance are so successful in containing the spread of the pandemic: They reduce the number of viruses to which one is exposed, he said Monday afternoon during a lecture.
In order to find out how many viruses are transmitted from person to person during an infection, Bergthaler and colleagues have been studying the genetic material of the viruses in carriers (infectors) and the people infected by them (infected persons). These pairs were identified by means of contact tracing.
Virus variants are decisive in infection
If the infected person carries only a few virus variants of the infector and is still sick, it means that it is dangerous to come into contact with even a few viruses. If many virus variants of the Infektktor are to be found with the infected one, many viruses are necessary, in order to release the illness, so the researcher of the CeMM belonging to the Austrian academy of the sciences (ÖAW) with an on-line lecture of the Viennese science, research and technology fund (WWTF), which financed also the study.
The scientists calculated that on average a good 500 viruses were transmitted per infection. All over the world, no data has yet been available on how many viruses are needed to cause Covid-19 disease, according to Bergthaler. Compared to other viral diseases, this number would be quite high.
“With HIV, it is assumed that a single virus is enough to start a new infection,” he said. In the case of influenza A (the only type of influenza virus that can spread worldwide) there are different figures in scientific studies. Some researchers speak of a single influenza virus, some of ten to a hundred viruses that can cause an infection.
Number of viruses also determines the severity of the disease
According to this research result, whether and to what extent someone falls ill with Covid-19 could be a “pure number history”, the Viennese scientist believes. If one gets a few viruses, the course of the disease would be weaker or one might not get sick at all.
It would also explain the benefits of simple physical measures such as mouth-nose masks and spacing, said Bergthaler: even if they do not prevent one from coming into contact with SARS-CoV-2, they could greatly reduce the number of viruses to which someone is exposed. This would massively reduce the spread of the pandemic and the waves of infection.
— Hector Pascua, Source: APA. Picture: stockilyapp.com
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