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Coronavirus, possible transmission without symptoms

2020-02-22T09:39:08.930Z


Experts, as for all respiratory viruses. Close proximity is enough (ANSA)


It has been discussed since the beginning of the new coronavirus epidemic and so far it has often happened that the positions of the institutional and scientific world were at odds on the possibility of the transmission of the SarsCov2 virus even in the absence of symptoms. However, even recent research finally brings order to the story.

All virologists have always been in agreement in supporting the possibility of asymptomatic transmission, but the first data relating to the new coronavirus date back to the end of January, with the description of a case of asymptomatic transmission in Germany in the New England Journal of Medicine. The same magazine has just published a Chinese study that indicates how the amount of coronavirus present in the nose and throat of asymptomatic people can reach levels comparable to those of patients with symptoms, making them potentially infectious. Cases of asymptomatic carriers of the virus were also present on the Diamond Princess ship before the quarantine took off.

"Asymptomatic contagion is technically possible, even if we have no information on how the virus can be released in an asymptomatic phase," said infectious disease expert Massimo Galli, of the University of Milan and head of the hospital Sacco.

"An asymptomatic phase exists for all viruses affecting the respiratory tract and depends on the quantity of viruses present in the organism", remarked Giorgio Palù, professor of Microbiology and Virology of the University of Padua. "The diffusion of viral particles - he added - takes place with the emission of aerosols also speaking with close contiguity, at a distance of one meter".

Palù also says that the period between the infection and the appearance of the fever falls into the risk period for asymptomatic transmission. Prudence is a must also considering that it is possible to be negative to the test that identifies the virus particles in the blood: this may depend on the point where the sample was taken with the swab, for example if from the throat or nose. It is also possible that the infection has passed from the superficial to the deep airways.

In light of these considerations, quarantine is an "absolutely necessary" measure to control the spread of the virus, said immunologist Antonio Lanzavecchia, director of the Research Institute in Biomedicine (Irb) in Bellinzona. "Since we have seen how a single person can bring an outbreak of infection, measures such as quarantine are absolutely necessary." This, according to the expert, can happen because "the contagiousness of a virus is variable" and "from the biological point of view one is not infectious only when one has the symptoms". It must also be considered that the spreading capacity of a virus is also typical of those who are convalescing, as is the case with influenza and other viral diseases.

The final word when it comes to symptom-free transmission is, however, the research conducted in China and just published in the New England Journal of Medicine. The data, noted the doctor Roberto Burioni with his colleague Nicasio Mancini, indicate that the amount of virus reaches its peak immediately after the appearance of the first symptoms, with high levels in the upper respiratory tract.

The other important element that emerges from this research is the ease with which coronavirus multiplies even in people without symptoms, resulting in quantities in the mucous membranes of the nose and throat: it is the confirmation, the two experts note, that "a greater amount of virus can, through mucus or saliva, reach a healthy individual, that is, the possibility of infecting it is higher ". It is a confirmation, they conclude, of how "even those who have no symptoms can transmit the infection".

Source: ansa

All tech articles on 2020-02-22

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