The survey found 26-32 infections per reported case in August, compared with 81-131 infections per reported case in the first round in May.
It is estimated that one in 15 people aged 10 years and older were exposed to the new coronavirus infection in August, indicating that a large part of the population is still susceptible to the virus, according to the second national serosurvey.
Releasing the findings on Tuesday, ICMR Director General Balram Bhargava said 6.6 percent of the 29,082 people (ages 10 and older) surveyed from August 17 to September 22 showed evidence of past exposure to the Covid-19. The prevalence was higher for adults (older than 18 years) with 7.1%.
This is a significant increase from the prevalence of 0.73 percent found in the first serosurvey, conducted between May 11 and June 4, among adults in 70 districts. The second survey was conducted in the same districts, but children (older than 10 years) were included.
Significantly, the second survey shows that children are also vulnerable to infection. “The seroprevalence was not different by age group or gender. All age groups older than 10 years were found to have been exposed to the infection. Previously, we had the impression that it does not affect those under 18 years of age. But we have discovered that there is no difference, ”said Bhargava.
“The data shows that a large proportion of the population is still susceptible. Prevention fatigue must be avoided and we must stick to the 5T strategy: test, track, trace, treat, and use technology. Non-pharmacological interventions such as physical distancing and the use of face masks remain essential. In light of the upcoming festivities, the winter season, and the mass gatherings, states must implement containment strategies in the most effective manner, ”Bhargava said.
The survey, which was conducted in a context of easing of restrictions and resumption of economic activity, reveals that the risk gradient is greater in urban marginal neighborhoods. The prevalence in urban slums stood at 15.6%, compared with 8.6% in non-slum urban areas and 4.4% in rural areas.
“… The risk gradient is greater in urban slums. Therefore, people-centered and risk-centered interventions need to be carried out more in urban slums; and older people and people with comorbidities must be protected, ”said Bhargava.
With increased testing over the past two months, the survey found 26 to 32 infections per reported case in August, compared with 81-131 infections per reported case in the first round in May.
“The new coronavirus infection has a much broader dimension. There are asymptomatic infected people, which is a well-known dimension. But what is striking is that in the latest results we estimate that with a confirmed case we found 81-131 cases. Now that number is 26-32. When we increase the tests, it is shown that we are tracking the virus with greater intensity. But remember, we can never, in an epidemiological sense, identify all asymptomatic individuals. That is why a serosurvey is an additional tool for contract tracking, ”said NITI Aayog member Dr. V K Paul.
Dr. Paul said data must be analyzed from two perspectives to implement future containment strategies. “The second extensive round was carried out in a systematic way … we have to look at the results from both sides. First, the (containment) measures adopted have kept the prevalence at lower levels, despite the unblocking and resumption of economic activity; second, it reveals that more than 90% of the population is susceptible to the virus. And the risk continues, ”he said.
“In winter, respiratory viruses spread faster. In the next five months, maintaining social distance and wearing a mask becomes even more important. The data is an indicator that we have to celebrate parties in small groups, “he said.
Responding to a question, Bhargava said that there are two ways of looking at the data. “Currently, we can say that our seroprevalence is comparable to serosurveys around the world; if you look at Switzerland (8 percent), the United Kingdom (7 percent), Belgium (5 percent), the United States (9.3 percent), ”he said.
“The serosurvey gives us data on exposure to the virus; whether the individual has developed a disease or not, that data is not there. Second, these are the statistically collected data from different districts, and we extrapolate the data and try to get a percentage … the first tool is testing, the second tool is looking at the serosurvey, and the third tool is looking at waters residuals to find the prevalence. They are epidemiological tools that guide us, ”he said.
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