Study finds that small number of infected and children spread the virus


posted on 01/10/2020 06:00 / updated 01/10/2020 10:44

(Credit: AFP / Arun SANKAR)

Second most populous country, behind China, India suffers from an explosion of cases of covid-19. There are officially 6.1 million infected with a virus that has high contagion power. For these reasons, India was chosen to be the stage for the largest contact tracking study of an illness ever conducted in the world. Researchers analyzed more than half a million people who were exposed to Sars-CoV-2 and were surprised by some results. One is that only a small percentage of those infected are responsible for the spread of cases. Scientists also noted the role played by children in spreading the coronavirus. The data were published in the latest issue of the journal Science and may help develop strategies to combat the disease in regions with more limited resources.

The scientists used data from 575,071 Indians exposed to the virus, with 84,965 having tested positive for Sars-CoV-2 infection. The information was collected from the beginning of the pandemic until August 1, in two states – Tamil Nadu and Andhra Pradesh. Through accurate screening of people who had contact with the sick, it was found that 71% of those infected did not infect their contacts. On the other hand, only 8% of people with the virus were responsible for 60% of new infections.

“Our article is the first major study to show that covid-19 over-spread depends on a small percentage of the infected population. A small group is the one who passes the virus on. This characteristic should be the rule and not the exception when looking at the spread of covid-19 both in India and, probably, in all affected places ”, emphasizes, in a statement, Ramanan Laxminarayan, senior researcher at the Princeton Environmental Institute (PEI ), in the United States.

Scientists have also identified the situations most at risk of contagion. The most dangerous interaction was in shared transport for six hours or more. “In these environments, there was a 79% risk of infection,” says the article. Living in a shared house comes next, at 60%.
Death cases occurred, on average, six days after the hospitalization of those infected – the average in the United States, another country also very affected by the pandemic, is 13 days, for example. In addition, deaths were concentrated among people aged 50 to 64 years, a slightly younger interval than the population at risk (over 60 years). “We found that the reported cases and deaths have been concentrated in younger groups than we expected, which differs from observations made in some high-income countries,” adds Laxminarayan.

Werciley Júnior, an infectious disease specialist and head of the Hospital Infection Control Commission at Hospital Santa Lúcia, in Brasília, points out that Indian data are in line with what has been observed during the spread of the coronavirus around the world. “These are conclusions that we already suspected, but we did not have a comprehensive analysis to prove them. We even have some countries that monitored infected people and people with whom they had contact, but on a smaller scale, such as Belgium and Sweden ”, he exemplifies.

The infectologist believes that the results obtained are essential to define measures that can contain the new coronavirus in other realities. “When you know how to broadcast within the community, it becomes much easier to create rules. Then, you will have the necessary background to ensure that they will have the expected success ”, he justifies. “Information of this type is valuable because it is very likely to be repeated in other countries, which can use it. They also serve as a basis for other studies that may complement the data already obtained. ”


Another point that drew attention to children and young adults, aged 20 to 44 years, constituted a third of the cases of covid-19 in the sample were especially important for the transmission of the virus in regions with limited resources. “Children are very efficient transmitters in this environment, which has not been firmly established in previous studies”, says Laxminarayan. “This is consistent with what we know about the flu, where children are among the main causes of infections. It shouldn’t be surprising to see this in another respiratory infection. ”

In the sample, they represented one third of the cases of covid-19. They were also more likely to be infected with the coronavirus from contact with people of the same age group. “The likelihood of this transmission is among the highest among children under 14 years of age. This shows that, even without schools functioning, which was the scenario in which we carried out our analysis, transmission from child to child seems to be very important ”, informs the text.

Infectologist Werciley Junior points out that the greatest spread among children reflects an important characteristic of the youngest. “As with other similar illnesses, we see that children contribute a lot to spread the disease. This is also because it is more difficult to isolate them, we are not able to maintain the distance that is made with adults. This factor, alone, already contributes a lot for the transmission rates to be higher among them ”, he explains.


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