More than 50% people in Delhi have been exposed to covid-19, suggests the sero survey

The fifth serological survey in Delhi to detect Covid-19 antibodies has shown that 56.13% of the 28,000 people sampled tested positive. Here is all you need to know about the findings that suggest more than half of the Capital’s population on average may have been exposed to the virus:

• The data showed that except for the north district, the other 10 districts had a seroprevalence of more than 50%. Of these, six had a seroprevalence of over 55%. South-east district had the highest at 62%.
• The numbers now appear to fall in a territory that experts believe is similar to the herd immunity threshold – a point in seroprevalence (estimated to be 60-80% of the population in case of Sars-Cov-2) when there are too few people left for the virus to spread to, slowing an outbreak down.

• Delhi health minister Satyendar Jain has cautioned that this should not be seen as having hit herd immunity.
• Experts have underlined herd immunity is uncertain in the case of natural infections since such immunity could wane and people still spread the disease while they are infected (contrary to what happens when someone is vaccinated).
• The latest round of the survey was conducted between January 15 and January 23 and included 100 samples from each of the city’s 272 wards.
• It was the largest in the Capital and the country so far.
• The high seroprevalence is in sync with the state of the outbreak in the Capital.
• Over the past 10-12 days, Delhi has been reporting less than 200 Covid-19 cases every day and the positivity rate, which at one point had touched 15%, is now stable at lower than 1% for the past one month.
• The full report of the latest survey will be released later this week after further examination of the findings.
• This time, too, the number of women having antibodies was more than that of men. There means that all these people had Covid at some point and now have fully recovered.
• Experts say the latest survey was bigger in scale and also better technology was used.

• CLIA technology was used for the latest survey, which is more sensitive than the ELISA technology.
• All the samples were tested to ensure uniformity. The survey was conducted in association with Maulana Azad Medical College. The samples were collected from people of all socio-economic strata and from across all kinds of population and age groups.
• Delhi’s first serological survey was done in June-July and it had shown that 23.4% of people surveyed had developed antibodies against the virus.
• Similar surveys in August showed that 29.1% of people had antibodies, 25.1% in September, and 25.5% in October.
• A positive result implies that the person has developed antibodies against the virus. This means that the person was infected at some point and developed immunity against it.