Coronavirus: six in ten infections come from …

A study published in the scientific journal JAMA network open indicates that 59% of new cases of coronavirus infections come from “asymptomatic transmission”, a figure that breaks down into 35 percent of new infections from people who don’t yet have symptoms (presymptomatic) and 24 percent who never have. These findings reaffirm that social distancing and the use of a chin strap remain the best allies to curb the spread of the virus.

The analytical model, recently published in this monthly medical journal of the American Medical Association, shows how transmission by asymptomatic people accounts for more than half of all cases. Although it is proposed that transmission from people infected but without symptoms can result from two different infection states: presymptomatic individuals (who are infectious before they develop symptoms) and people who never show symptoms (asymptomatic or never symptomatic infections).

Experts analyzed the relative amount of contagion from presymptomatic, never symptomatic and symptomatic patients in different scenarios in which the proportion of transmission of people who never develop symptoms (i.e. remain asymptomatic) and the infectious period have varied according to best published estimates. The model’s basic assumption was that peak infectivity occurs in the median of symptom onset, that 30 percent of those infected never develop, and that 75 percent are as contagious as those who do. develop symptoms. Taken together, these basic assumptions imply that infected people who never develop symptoms can account for 24 percent of all transmissions.

Thus, the results show how 59 percent of all transmissions are from asymptomatic transmission, based on the model’s baseline scenario.

“Under a wide range of values ​​for each of these assumptions, it is estimated that at least 50% of new SARS-CoV-2 infections come from exposure to people who are infected but without symptoms,” the scientists explained. of the Centers for Disease Control and Prevention (CDC), which carried out the research.

At the same time, they declared that in addition to identifying and isolating people with symptomatic Covid-19, “to effectively control the spread it will be necessary to reduce the risk of transmission from infected people who are not showing symptoms.”

“Measures like use of masks, hand hygiene, social distancing and strategic screening of people who are not sick will be essential to slow the spread of the disease, until safe and effective vaccines are available and widely used, ”they concluded.