Children are active transmitters of Covid-19, reveals a new study, which also shows that just 8 per cent of the patients are the source of 60 per cent of new infections, while 70 per cent of those infected do not transmit the disease to anyone else. This shows that the transmission of Covid-19 in India has been driven mainly by super-spreaders.
The world’s largest contact tracing study was carried out by the Centre for Disease Dynamics and Policy (CDDEP) in Tamil Nadu and Andhra Pradesh on 5,75,071 individuals exposed to 84,965 confirmed Covid-19 cases. The study, led by Ramanan Laxminarayan, Director of CDDEP, has been published in the journal Science.
The study showed that both cases and deaths due to the disease have been more heavily concentrated in the 40-69 year age group. The researchers found a high prevalence of infection among children. The study showed a high prevalence of infection among children who were contacts of cases around their own age.
In the 5 to 17 years age group, for every 100 index patients, 15.4 of their contacts tested positive. This was the highest percentage among several age groups analysed in the study. This was followed by the 18 and 39 age group years. They infected 12.3 per cent of their contacts each, followed by those in the 40 to 49 age group.
“School closures and other pharma interventions have reduced contacts among children and that social interaction among children may be conducive to transmission,” the report said.
According to the scientists, the findings offer a peek into the pandemic’s trajectory. The study noted that contacts with the same age were associated with the greatest infection risk — a pattern, which the researchers said, was strongest among children between 0-14 years of age, and among adults older than 65 years. They said the proportion of deaths to the number of infected people, known as the case-fatality ratio (CFR), spanned 0.05 per cent at ages 5-17 years to 16.6 per cent at ages exceeding 85.
Follow-up testing of exposed contacts revealed that 70 per cent of infected individuals did not infect any of their contacts.
The researchers said this finding presents the largest empirical demonstration of superspreading, which is when an unusually large number of individuals are infected by few other people. They said the findings “may indicate the identification of less-severe infections through active case-finding.”
Andhra Pradesh and Tamil Nadu are among the top Indian States with the largest healthcare workforce and public health expenditures per capita and are known for their effective primary healthcare delivery models, the study noted. It said 63 per cent of those who died had at least one co-morbidity, and 36 per cent had two or more underlying health conditions that made them more susceptible to the disease. About 45 per cent of those who died were diabetic.
Unlike observations in high-income countries, they said the deaths in India are concentrated at ages 50-64 years. In the two Indian States in particular, they said only 17.9 per cent of Covid-19 deaths occurring on or before 1 August, 2020 were among people older than 75, compared with 58.1 per cent of deaths due to the disease in the US.