Coronavirus: new study shows role of children and super-spreaders

Why do children get less sick from covid-19?

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(CNN) -

Children can efficiently transmit the coronavirus to each other, but young adults are the main source of the spread of COVID-19, according to a study published Wednesday.

The study, based on a gigantic contact tracing effort involving more than 3 million people in India, shows that the majority of COVID-19 patients never infected anyone else.

The researchers found that 70% of the infected people did not infect any of their contacts, while 8% of the patients were responsible for 60% of the new infections observed.

The study also contradicts the widely held belief that children are unlikely to contract the coronavirus.

We discovered something else.

They are getting infected in significant numbers, ”study leader Ramanan Laxminarayan, from the Center for Disease Dynamics, Economics and Policy in New Delhi, and also from Princeton University, told CNN.

"Although the role of children in transmission has been debated, we identified a high prevalence of infection among children who were case contacts close to their own age," the team wrote in their report, published in the journal Science.

And that's despite the fact that schools have been closed in India since March, Laxminarayan noted.

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The study involved universal contact tracing efforts conducted in two large states in South India.

Authorities tracked and tested more than 575,000 people exposed to nearly 85,000 confirmed coronavirus cases from March through August.

"This is the largest contact tracing study in the world, and by far," Laxminarayan said.

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"We were surprised to find that only 8% of the primary infected cases were responsible for 60% of the contacts that were infected," he said.

That is a hugely disproportionate effect.

Overpropagation has been suspected, but not really documented, ”he explained.

Most of the index cases - the first patient in a chain of transmission - were adults ages 20 to 45, the team found.

“The youth to middle-aged group is the one that is coming into contact with people.

They are the people most likely to be away from home.

They are the ones who carry the disease from one place to another, "said Laxminarayan.

The study also showed that the closures worked.

The restrictions lowered the transmission rate, the team found.

Case fatality rates, a measure of death rates, also decreased over time.

"Those who tested positive in May and June were 13% less likely to die than those who tested positive in March and April," Laxminarayan said.

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