more than half of new infections come from asymptomatic

As the cases of Covid-19 began to spread around the world, scientists observed that, difference from the coronavirus that caused the 2003 epidemic, the spread of SARS-CoV-2 could not be contained by detection based solely on symptoms.

According to scientific publications at the time, asymptomatic and clinically mild infections were rare in SARS-CoV 2003. Furthermore, no cases of transmission were reported before the onset of symptoms. However, the new coronavirus has spread faster than the old one and tests have shown that it is spread to people without symptoms.

What remains to be seen exactly is the proportion of Covid-19 infections associated with these patients. The JAMA Network Open magazine published research highlighting how transmission from people without symptoms accounts for more than half of all cases.

Its authors, scientists at the Centers for Disease Control and Prevention (CDC) in Atlanta, United States, say that identifying and isolating only people with symptomatic Covid-19 will not help control current propagation SARS-CoV-2.

Transmission from people who are infected but have no symptoms can result from two different states of infection: individuals presymptomatic (who are infectious before symptoms appear) and people who never feel symptoms (asymptomatic or never symptomatic infections).

Experts analyzed the relative amount of contagion from presymptomatic, never symptomatic and symptomatic patients in different settings in which the proportion of transmission of people who never develop symptoms (i.e. they remain asymptomatic) and the infectious period have varied according to the best published estimates.

The importance of people without symptoms

The model’s basic assumption was that peak infectivity is in the median of symptom onset, that 30% of those infected never develop symptoms, and that 75% are as contagious as those who do. symptoms. Combined, these basic assumptions imply that infected people who never develop symptoms may account for about 24% of all transmissions.

Thus, the results show how 59% of all transmissions are from asymptomatic transmission, according to the model’s baseline scenario. In contrast, 35% of new cases come from people who infect other people before showing symptoms (presymptomatic individuals); and 24% of people who never develop symptoms.

“Based on a wide range of values ​​for each of these assumptions, it is estimated that at least 50% of new SARS-CoV-2 infections result from exposure to people infected but without symptoms“say CDC researchers.

The authors assure that in addition to the identification and isolation of people with symptomatic Covid-19, to effectively control the spread, it will be necessary to reduce the risk of transmission from infected people who do not show symptoms. .

“Measures like use of chin straps or masks, hand hygiene, social distancingStrategic screening and screening of people who are not sick will continue to be essential in slowing the spread of the disease until safe and effective vaccines are available and widely used, ”they conclude.

(Source: Agence Sinc.es)