New Delhi : In Tamil Nadu and Andhra Pradesh which are among the leading states in terms of Covid-19 caseloads, new research has revealed that the cases and deaths are concentrated in younger cohorts than expected from observations in higher-income countries, a finding that "may indicate the identification of less-severe infections through active case-finding".
Researchers led by Ramanan Laxminarayan, Director of the Washington-based Centre for Disease Dynamics, Economics and Policy, found that while the role of children in Covid-19 transmission has been debated, "we identify high prevalence of infection among children who were contacts of cases around their own age".
The risk of transmission was highest among pairs of contacts of the same age.
Of all same-age pairs, the likelihood of transmission was among the highest between pairs of children under the age of 14.
"Same-age contacts were associated with the greatest infection risk, a pattern strongest among children ages 0-14 years and among adults older than 65 years. The case-fatality ratios spanned 0.05 per cent at ages 5-17 years to 16.6 per cent at ages exceeding 85," the researchers wrote in the study published in the journal Science.
Tamil Nadu recorded 5,659 positive cases of Covid-19 on Wednesday, bringing the state tally to 5,97,602. Among these, Chennai reported 1,295 positive cases, bringing the city's total to 1,67,376.
Andhra Pradesh registered 6,133 new coronavirus infections, taking its total tally to 6.9 lakh cases, even as 7,075 more recoveries on Wednesday brought down the active cases to 58,445.
According to the researchers, both states began rigorous disease surveillance and contact tracing early in response to the pandemic.
To reach the conclusion, Laxminarayan and colleagues analysed surveillance and contract tracing data from these two states' programmes.
Epidemiological data and laboratory test results were available from 575,071 tested contacts of 84,965 confirmed cases.
The authors noted that estimates of time-to-death in both states is rapid as compared to what has been observed internationally (for example 13 days to death from the date of hospital admission in the US, compared to succumbing to death within six days in the two Indian states, for about half of the cases ascertained in this study).
The most prevalent conditions among those who died were diabetes, sustained hypertension, coronary artery disease, and renal disease, with at least one comorbid condition noted among 62.5 per cent of fatalities, in comparison to 22 per cent of fatalities in the US (as of May 30).
In the two Indian states, only 17.9 per cent of Covid-19 deaths occurring on or before August 1 were among people older than 75, compared with 58.1 per cent of Covid-19 deaths in the US.
The results, from a study based on surveillance and contact tracing data, offer a window into the pandemic's trajectory in a low- and middle-income country, where most Covid-19 cases have occurred, and from which insights to guide control measures are urgently needed.
The authors noted several implications and limitations of their study.
"Similar studies are necessary to inform the successful adoption of epidemic control measures in low-resource settings globally," they wrote.