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2nd wave coming: Serosurveys had raised red flags — but little else

In January, when almost every state was reporting a decline in case numbers, Kerala was witnessing a surge -- contributing almost half of all cases in the country. By mid- February, the confirmed cases in the state had crossed 10 lakh, second only to Maharashtra.

Written by Amitabh Sinha , Kaunain Sheriff M | Gaya, New Delhi |
April 19, 2021 4:30:34 am
2nd wave coming: Serosurveys had raised red flags — but little elseA testing camp at Sabarmati railway station for those returning from Kumbh mela Sunday. (Express photo by Nirmal Harindran)

IT doesn’t need a galaxy of experts to list what’s needed: boosting Covid vaccination, augmenting oxygen and beds, expanding genome sequencing, ramping up testing and tracing, bringing down the infection level — all of this double quick.

But as the second wave climbs higher each day, both in cases and deaths and the Centre and states scramble to respond, there’s a growing — and grudging — acceptance that one obvious fact eluded many. That, in a population of a billion plus, a pandemic doesn’t vanish as it seemed to do barely a couple of months ago. That a second wave was going to come.

“We were quite lucky to have this wonderful window of opportunity between November and January when the curve was falling across India,” said Virander Singh Chauhan, former director of the International Centre for Genetic Engineering Biotechnology.

Migrant workers coming from Mumbai at Charbagh Railway Station in Lucknow on Monday, April 12, 2021. (Express file photo by Vishal Srivastav)

“Unfortunately, it served to instill a false sense of security. Everyone thought the virus had magically disappeared when anyone with a basic idea of infectious diseases knew it was lurking very much within us and could strike anytime…There are several things we should have done during this time but, I have to say it, we messed it up big time,” Chauhan said.

To be sure, a falling Covid curve, a low fatality ratio, a large young and asymptomatic population and the economic and social imperatives of opening up, meant that the second wave was inevitable. But the four-month lull, experts agree, could have been used to not only anticipate this wave but design policy interventions. Instead, guards were lowered, critical signs ignored.

Beginning with serosurveys – that vital indicator of disease prevalence. These involve blood tests to check whether a person has been infected with a disease in the recent past. They help track the geography of the disease, its age-wise or gender-wise break-up and levels to which testing needs to be ramped up.

Delhi Covid A health worker collects a sample for testing from a person at Delhi’s Anand Vihar. (Express photo by Amit Mehra)

The Indian Express spoke to several officials and experts at the Centre and the states and found that in state after state, serosurveys underlined that the second Covid wave was coming (see chart) and yet little was done with the data or as follow-up.

Indeed, in January, when almost every state was reporting a decline in case numbers, Kerala was witnessing a surge — contributing almost half of all cases in the country. By mid- February, the confirmed cases in the state had crossed 10 lakh, second only to Maharashtra.

This “outlier” trend in Kerala was not very well understood until the state did a serosurvey in January-February in all its 14 districts. It revealed that only about 10% of the state’s population had been infected. In other words, a majority was still susceptible.

Importantly, the survey offered clues to the state’s high case count. For, Kerala had identified and tested at least one of every four infected individuals. In the country as whole, this number, estimated from a prior serosurvey, was just one in about 30.

Another insight the state gleaned from the serosurvey was that the risk of infection among those 70 years or above was significantly less, indicating that reverse quarantine – where the vulnerable are isolated – was effective.

Such granular detail was not captured in many states. At the national level, the Indian Council of Medical Research has conducted three serosurveys, the last one in December. Serosurveys have been done in at least 10 states and many cities, including Delhi, Mumbai, Pune, Ahmedabad, and Chennai, but few have done it at regular intervals.

The WHO listed a total of 37 serosurveys in India until March 10. It includes the three national serosurveys, 14 regional and city level exercises, and 20 others at a more local level by medical and health institutions.

However, many states currently witnessing a major surge in cases including Chhattisgarh, Bihar and Punjab, do not appear in this list compiled by the WHO.

But serosurveys are not a one-off exercise. As the nature and behaviour of the virus changes constantly, scientists say, there is a need for regular monitoring and surveillance through serosurveys in different population groups. This has hardly happened.

More concerning has been how the data was interpreted. The December serosurvey, whose results were announced in early February, for example, showed that barely 20 per cent of India’s population had been infected by then. That was a red flag: it meant a fresh wave was possible even though one couldn’t predict when.

However, some small very localised clusters in Delhi, Mumbai and Pune showing more than 50 per cent seropositivity received far greater prominence, and were used to explain why the numbers were falling.

“It was a classic case of cognitive bias,” said an official who did not want to be named. “We wanted to believe that the Covid is on its way out and so we interpret data to reinforce that belief. We were even talking about herd immunity for an entire city based on a serosurvey in a few neighbourhoods of a small sample.”

That’s why the current wave of infections calls for more regular, and geographically spread-out serosurveys. “The second wave is very different from the first and we do not fully understand why or in what manner. There is anecdotal evidence of this being less deadly, or affecting a different age-group but in the absence of scientific data, the policy responses are likely to bring less than optimum results,” said a scientist tracking these surveys.

There is another reason why serosurveys have become very important. There is a growing number of cases that can potentially be classified as re-infections. The most robust way of confirming reinfections is through gene analysis but that takes time and money. Cases of reinfections can be flagged very easily through these serosurveys. A good estimate for reinfection rate would have implications for a variety of responses, including the deployment of vaccines.

Niti Aayog member Dr V K Paul, head of India’s Covid19 task force, admits there is a need for more robust data. “We know from local serosurveys that in densely populated areas, the virus has gone deeper. However, the overall picture shows that… (people) can still get infected. Therefore, we should not have large gatherings. Only then, will the situation be under control…In our country, there is still a very large population that continues to be vulnerable,” he said.

Giridhara R Babu, a member of Karnataka’s COVID-19 Technical Advisory Committee, said the panel, on the basis of a serosurvey, had in November itself flagged that a second wave would hit the state late February.

“In Karnataka, there was no confusion; they knew a second wave is coming,” said Babu. However, he underlined that the serosurvey is only one of the tools. “Using serosurveys to prepare for the second wave is just one part of the story. You need to have the intent to prepare for the second wave….Now there is enough evidence that the third wave will also come,” Babu said.

(Part 2: First strain of concern in October but why genome studies delayed)

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