- One in every 15 exposed to virus by August, shows sero survey
- Urban slum, non-slum areas had higher Covid prevalence than rural areas
- 2nd sero survey was conducted by top medical body in same 700 villages
Around 7.1 per cent of India's adult population (aged 18 and above) showed evidence of exposure to the coronavirus by the end of August, the results of the second national sero-survey, conducted by top medical body ICMR between August 17 and September 22, have revealed.
This is a massive increase from the 0.73 per cent logged in the first survey, which was conducted across the same 700 villages and urban wards as the second, between May 11 and June 4.
Worryingly, the findings of the second sero-survey showed there is still a considerable section of the population that has not yet been exposed to the virus and remains at risk of infection.
Specifically, the sero-survey showed that only one in 15 people (aged 10 and above) had likely been exposed to the virus by the end of August, with the risk of infection two times higher in slums as compared to non-slum areas of urban centres, and four times higher than rural areas.
According to the data sero-prevalence among people in urban slums was 15.6 per cent. It was 8.2 per cent for those in non-slum areas of urban centres and only 4.4 per cent in rural areas.
The first survey found sero-positivity was highest in villages (rural areas) with 69.4 per cent compared to 15.9 per cent in urban slums and 14.6 per cent in non-slums. However, that survey said only about a fourth (25.9 per cent) of surveyed clusters were from urban areas.
Overall, for every confirmed COVID-19 case in August there were 26 to 32 infections that went undetected - a result, the government said, of improved contact tracing and tracking. The same figure was 81-130 in May.
The second sero-survey was conducted across the same 700 villages and (urban) wards from 70 districts in 21 states visited for the first (which was conducted between May 11 and June 4).
Blood samples from 29,082 people - compared to 28,000 in the last survey - were tested. The tests look for IgG antibodies, which indicates exposure to the novel coronavirus.
Mumbai showed the highest sero-prevalence with 57.8 per cent of samples (from slums) testing positive. The rate dropped to 17.4 per cent for samples from non-slum areas.
Delhi recorded a 29.1 per cent sero-prevalence in the second round of sampling that was conducted between August 1 and 7. This was higher than the 23.1 per cent recorded in the first round conducted between June 27 and July 10.
Surprisingly, Puducherry was next with a sero-prevalence of 22.7 per cent in the seond round (September 10 - 16); the Union Territory has recorded around 27,000 confirmed cases so far, of which 515 are deaths and 5,014 are active cases.
Puducherry's sero-prevalence was only 4.9 per cent in the first round of survey - August 11 - 16.
Chennai recorded a sero-prevalence of 21.5 per cent and Ahmedabad 17.6 per cent, with Indore in Madhya Pradesh registering 7.8 per cent.
Each of these figures correspond to two different sero-surveys that were conducted independently of each other.
The results, presented by the Union Health Ministry on Tuesday afternoon, also highlighted a lower infection-to-case ratio in August compare to May - a reflection, the ministry said, of a substantial increase in testing and detection across the country.
The sero-survey also highlighted the necessity of assiduously practicing "non-pharmacological interventions" - social distancing, proper cough etiquette and the use of face masks and hand sanitisers - to ensure limited spread of the virus.
Elderly people, individuals with co-morbidities, children and pregnant women remain susceptible to infection and still need to be protected, the government stressed.
The government also warned people that with the holiday season around the corner and the number of festivals that will be celebrated, mass gatherings needed to be strictly avoided. State governments, the centre said, must come up with "inventive containment strategies" for this.
India has over 61 lakh confirmed Covid cases so far. Over 70,000 new cases were detected in the past 24 hours, government data showed this morning, and 776 people died.