A paper published in the journal Science on Wednesday has used data from two Indian States, Tamil Nadu and Andhra Pradesh, to provide key insights into the epidemiology and transmission dynamics of COVID-19 in resource-limited populations.
It used surveillance and contact tracing data, which are critical components of an effective public health response to COVID-19, from these two States, to generate observations that might also work in other similar low- and middle-income settings.
The authors of the paper, titled ‘Epidemiology and Transmission dynamics of COVID-19 in two Indian states’, include the Health Secretaries of Tamil Nadu and Andhra Pradesh, J. Radhakrishnan and K.S. Jawahar Reddy, Ramanan Laxminarayan of Center for Disease Dynamics, Delhi, and researchers from Princeton Environmental Institute and Center for Computational Biology, University of California, Berkeley.
Much of the information about COVID-19 so far has been from China, Europe and the United States (U.S.). “Although most COVID-19 cases have occurred in low-resource countries, little is known about the epidemiology of the disease in such contexts. Data from the Indian states of Tamil Nadu and Andhra Pradesh provide a detailed view into SARS-CoV-2 transmission pathways and mortality in a high-incidence setting,” the paper stated.
Both States recorded their first laboratory-confirmed case on March 5 and are among those with the largest healthcare workforces and public health expenditures per capita. They are known for their effective primary healthcare delivery models and initiated rigorous disease surveillance and contact tracing early in response to the pandemic, the researchers stated.
“Our analysis suggests substantial variation in individuals’ likelihood of transmitting: no secondary infections were linked to 71% of cases whose contacts were traced and tested,” the paper added. It also identified high prevalence of infection among children who were contacts of cases around their own age. School closures and other non-pharmaceutical interventions during the study period may have contributed to the reductions in contact among children.
The analyses of fatal outcomes revealed an overall case-fatality ratio of 2.1%. They averred that a lower relative incidence of COVID-19 among older adults in Tamil Nadu and Andhra Pradesh has contributed to stark differences in the overall case fatality ratio and age distribution of decedents, in comparison to observations in the United States and other high-income countries.
Prospective testing of a large sample of exposed individuals through integrated active surveillance and public health interventions provided an opportunity to characterise secondary attack rates, identify risk factors for transmission, and account for deaths outside of healthcare settings, the paper added.
