FM November2020 Digital P

In mid-May, when India’s centrally
imposed lockdown restrictions began
to ease up, the Indian Council of Medical
Research (ICMR) launched a nationwide
cross-sectional serosurvey in over 26,000
individuals in 70 districts. The survey
included only the containment zones of the
10 cities reporting the highest number of
cases as of April 25.
The long-awaited results of the initial
study — published in the Indian Journal of
Medical Research on September 10, 2020
— arrived at the conclusion that the national
seroprevalence rate was only 0.73% among
the general population, excluding the
hotspots of 10 cities.
The second national serosurvey, whose
findings were published at the end of
September, revealed that seropositivity
levels had reached 7%. Despite the 10-
fold jump in the rates, it highlighted
the continued vulnerability of a massive
seronegative population base.
The objective of the second study,
which was carried out among the 29,082
people across 70 districts in 21 states
between August 17 and September 22, was
to estimate the prevalence of SARS-CoV-2
infection among individuals aged 10 years
and above, ICMR said.
Around 6.6% of individuals aged 10
and above and 7.1 percent of the adult
population aged 18 and above showed
HIGH INFECTION NUMBERS,
BUT LOW IN PREVALENCE
evidence of past exposure to the virus.
At 8.2%, the infection prevalence was
found nearly double in urban non-slums
compared to rural areas (4.4 percent).
The infection rate was the highest at 15.6
percent in urban slums.
The country-wide prevalence of the
THE SURVEYS FOUND THE
INFECTION PREVALENCE IS
NEARLY DOUBLE IN URBAN
NON-SLUMS COMPARED TO
RURAL AREAS. THE RATE OF
INFECTION IS THE HIGHEST IN
URBAN SLUMS
virus was similar to that seen in the United
States at the time, which was around 9.3%.
Brazil and Spain had a prevalence of 2.8%
and 4.6%, the ICMR said.
City surveys
In May, the country’s apex body governing
biomedical research advised states to
conduct periodic serosurveys to measure
coronavirus exposure in the population
using the IgG ELISA test.
Municipal corporations of major cities
in India, including Delhi, Mumbai and
Ahmedabad, released the results of the
COVID-19 seroprevalence surveys that they
had conducted in association with research
institutes.
The data from these surveys provide us
some insight into the infection prevalence in
urban Indian populations.
National Centre for Disease Control
(NCDC), under the health ministry, in
collaboration with the Delhi government
carried out a community-based crosssectional
serosurvey in all the 11 districts of
Delhi between June 27 and July 10.
After analysing 21,387 sera samples,
the study found that average infection
prevalence across Delhi from mid-June to
the third week of the month was 22.86
percent. This indicated that about 4.6
million individuals out of over 20 million
population in Delhi were infected, even
though the official tally ranged from 43,000
to 82,000 during that period.
Though smaller in size, the Mumbai
serosurvey was undertaken by a joint
venture between Tata Institute of
Fundamental Research (TIFR), Mumbai;
Translational Health Science and Technology
Institute (THSTI), Faridabad, Haryana;
University of Chicago, United States; Duke
SURVEY JIGSAW
While the average national
seropositivity is very low,
urban centres report very
high prevalence of
SARS-CoV-2 infection
India
7%
Mumbai
50%
New Delhi
29%
60 percent of the population is infected.
The “revelation” that the great majority
of the 1.3 billion-strong Indian population
is still susceptible to the infection came as
nothing less than a shock to those waiting
for redemption from the pandemic by way
of ‘herd immunity’.
They found the data at odds with the
steady surge of daily case counts seen through early October
which saw the country emerge as the world hotspot for
COVID-19.
“The entire country is looking forward to achieving herd
immunity,” said Dr Behram Pardiwala, Director, Internal
Medicine and Academics, Wockhardt Hospitals, South
Mumbai, echoing a widely held sentiment. “Once, herd
immunity is reached, the pandemic will surely end.”
28 / FUTURE MEDICINE / November 2020