Since the beginning of the Covid-19 pandemic, there have a been a large number of seroprevalence surveys – or “serosurveys” for short – to ...
Since the beginning of the Covid-19 pandemic, there have a been a large number of seroprevalence surveys – or “serosurveys” for short – to estimate how many people have been infected with the disease. These involve sampling populations at national, state, district, city, or even ward level, to estimate “seroprevalence”, that is, to find how many have antibodies to SARS-CoV-2, the virus responsible for Covid-19. With a third national serosurvey now completed, what are some of the lessons from past serosurveys?
Serosurveys have provided insights into the pandemic that aren’t readily visible in data on cases or recorded deaths. Remember that “cases” are recorded infections, confirmed using some test such as RT-PCR, and we expect these to be the tip of the iceberg of total infections; serosurveys on the other hand should indicate the true fraction of the population who have been infected.
The surveys have taught us that urban spread – particularly in city slums – can be very rapid indeed, and that new surges are possible even when a large part of a population has had the disease (as in Mumbai and Delhi). They have highlighted highly variable disease surveillance across the country, with weaker surveillance in some states, in rural areas, and...
