Researchers from the Government of Tamil Nadu and Andhra Pradesh, have performed one of the largest Covid-19 epidemiology studies to date, and have found that, among other patterns, both cases and deaths from the disease have been more concentrated in India in the 40-69 age group than is seen in high-income countries.
The research, reported on Wednesday in the journal Science, examined the trends of disease transmission in 5,75,071 individuals exposed to 84,965 confirmed Covid-19 cases in the two states based on data obtained from hundreds of thousands of contact tracers. According to the researchers, the results give an insight into the course of the pandemic in a low- and middle-income country where most cases of COVID-9 were reported.
Based on the results, the researchers suggested that both cases and deaths were concentrated in younger cohorts in the two Indian states than predicted from observations in higher-income countries. The study showed that same-age interactions were associated with the greatest risk of infection, a trend that researchers said was highest among children between the ages of 0-14 and adults, 65 and older.
The proportion of deaths to the number of infected individuals, referred to as the case-fatality ratio (CFR), ranged from 0.05 percent at ages 5-17 to 16.6 percent at ages greater than 85 years, they said. The researchers also noted that in the two states, Covid-19 patients have a median hospital stay of five days until death compared to 13 days till death.
Follow-up monitoring of exposed contacts showed that 70% of infected individuals did not infect any of their contacts, although 60 % of new infections observed accounted for 8% of coronavirus-positive patients. This result provides the largest observational presentation of super spreading, the researchers said. They said the findings may suggest the identification by an ongoing case-finding of less-severe infections.
The study noted that Andhra Pradesh and Tamil Nadu are among the Indian states with the highest per capita healthcare workforce and public health expenses, and are known for their successful models of primary healthcare delivery. It reported that 63% of those who died had at least one co-morbidity and that 36% had two or more underlying health conditions which made them more susceptible to the disease. The scientists said that about 45 percent of those who died were diabetics. They said that, unlike findings in high-income countries, the deaths in India are concentrated between ages 50-64 years.
Results on the spread and mortality of diseases can inform the Covid-19 combat strategy. The study also discusses the potential of India’s research to help inform the international solution to Covid-19.