COVID-19 in India: large study shows surprisingly low death rates among elderly: ScienceMag.

A large study of India’s COVID-19 cases, with nearly 85,000 index cases, shows some surprising differences from the experiences of other countries. As you may have heard, India has reached over six million cases; we expect the total confirmed case count to exceed that of the US in the next month, although the known death count is much less and the number of cases per capita is also less than that in the US.

This is the first large study from a country with a low socioeconomic status, giving important information about the disease in poor people with few resources.

The study was published as a preprint in Science magazine on September 30, 2020. Here is the abstract:

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. Reported cases and deaths have been concentrated in younger cohorts than expected from observations in higher-income countries, even after accounting for demographic differences across settings. Among 575,071 individuals exposed to 84,965 confirmed cases, infection probabilities ranged from 4.7-10.7% for low-risk and high-risk contact types. Same-age contacts were associated with the greatest infection risk. Case-fatality ratios spanned 0.05% at ages 5-17 years to 16.6% at ages ≥85 years. Primary data are urgently needed from low-resource countries to guide control measures.

https://science.sciencemag.org/content/early/2020/09/29/science.abd7672

Here are the prime findings from this study:

• An extensive contact-tracing effort (over 3 million exposed contacts with over half a million tested) found that most infectious contacts were with people of roughly the same age, especially for the youngest and oldest groups.
• Case-fatality rates were lower than expected for elderly individuals– mortality rates levelled off after age 65. This may reflect a healthier group of people among the very old in India.
• The highest risk of infection was among household contacts (about 10%), but the few cases who were examined with prolonged exposure during travel showed extremely high risk of contact infection (about 80%).
• 71% of cases did not pass on the infection to anyone, but a small proportion of cases passed it on to many people (super-spreaders.)
• Time from hospital admission to death averaged five days, whereas in the US it averaged two weeks. This may reflect weak hospital care.
• Even the youngest children passed on the infection to others at similar, significant rates– showing that children do pass it on.

These findings reflect better contact-tracing in that country, showing what can be done with effort. They also show that children are effective spreaders of COVID-19, contrary to assertions that some have made.