WHO to meet Indian team on high sero-positive rate

The World Health Organization (WHO) will hold a meeting with an Indian delegation later this week to analyse the unusually high rate of exposure to the novel coronavirus found in the sero-surveillance studies conducted in Delhi and Mumbai.
“What we are finding generally is that most of the sero prevalence results find that less than 10% of the population is positive, sero-positive, indicating that they had an infection… But the two studies that you point out in India are indeed very, very interesting and we need to look at a few things,” said Maria van Kerkhove, WHO’s technical lead for covid-19 emergency programme.

The WHO will look at whether the studies focus on a specific population, or a wider population, and the assays used. “We will fold these into our general understanding and we look forward to hearing from the actual researchers who were carrying out these studies, later this week,” she said.

A sero-surveillance conducted by the Union health ministry in New Delhi found that 23.48% of the national capital’s population had a history of being infected with SARS-CoV-2, the novel virus that causes covid-19. Another study conducted on 6,936 people from three municipal wards in Mumbai found that 57% of participants in slums had been exposed to and developed antibodies against SARS-CoV-2 virus. In residential societies of the city, the study found a 16% exposure rate.

The high exposure rate led to concerns that the number of people who were exposed to the virus could be multifold, compared to the people who were tested positive through RT-PCR tests.

A RT-PCR test detects if a patient has contracted covid-19, while sero-surveillance is conducted through antibody tests on blood, which look at whether a person has a history of infection to the virus and developed immunity to it. Sero-surveillance usually shows a higher rate of exposure to the disease compared to the number of patients diagnosed with the disease. In India’s case, the difference has been stark.

At 1.8 million, the total number of patients who tested positive in RT-PCR test in India is less than 1,000 per million population. In Delhi, the number of patients who tested positive is less than 0.7% of the city’s population against the 23.48% recorded in the survey.

The WHO on Monday also expressed concerns over the rising positivity rate, which is the proportion of people testing positive compared to the total number of tests, and the spread of the disease in rural India, which has poor health infrastructure.

“The worrying aspect is that the positivity rate continues to increase and is now at about 12.5%. So, it does demonstrate that the disease is circulating intensely. As I said, India is a large country…, but the disease is moving around from urban to rural and back to urban,” said Michael Ryan, WHO’s executive director for its health emergencies programme. – Livemint