PUDUCHERRY: Seroprevalence studies at JIPMER have found a 26 times higher proportion of COVID infection in Puducherry than earlier detected by the Real-time PCR till July.
Seroprevalence surveys use serology tests to identify people in a population or community that have antibodies against an infectious disease.
The seroprevalence study has found 4.9 per cent positivity as compared to 0.19 per cent positivity detected through RT-PCR tests, according to a release from JIPMER Director Dr Rakesh Aggarwal.
The study indicates that one in 20 people in Puducherry district showed evidence of coronavirus infection by the end of July 2020.
Survey to detect the extent of virus
In an attempt to find the extent of the spread of novel Coronavirus infection (SARS-CoV-2) in the population of Puducherry, JIPMER conducted a community-based survey to study the presence of antibodies in the blood (serum).
Of the total of 869 adults tested, 43 had antibodies against novel Coronavirus (4.9 percent). The positivity rate for antibodies was higher in the city (urban) population than in the rural population (5.7 per cent in an urban population in comparison to 3.1 per cent in rural) and among women than in men (6.3 per cent in women in comparison to 3.6percent in men).
The results of this study reflect the occurrence of exposure in people residing in Puducherry by 24th July 2020.
On the other hand, the total number of confirmed cases in the district by that date (July 24) was 2,271, with a cumulative incidence of 0.19 per cent for the population of Union territory (=2271/12,00,000). Thus, the proportion of persons with the presence of antibodies in the blood was nearly 26-fold (4.9/0.19) higher than that of the cases diagnosed by Real-time PCR test as on 24th July, explained the Director.
Experts from the Departments of Preventive and Social Medicine and Microbiology of JIPMER were involved in the selection of patients and collection of blood samples, the conducting of the tests as well as analysis of the results.
Survey details
For this study, blood was collected from randomly-selected adults aged 18 years and above from 30 different clusters, with a ratio of 21 from urban and 9 from rural areas to reflect the population distribution of the Union Territory of Puducherry.
The samples were collected during the period of 11-16th of August 2020.
Tools used in survey
The presence of antibodies was studied using an immunoassay (Elecsys® Anti-SARS-CoV-2; Roche) with a reported sensitivity of 99.5 per cent and specificity of 99.8 per cent at more than 14 days after exposure to the virus.
JIPMER proposes to undertake a repeat survey in the second or third week of September 2020 to assess the extent of exposure by the last week of August 2020 and further serial surveys at appropriate time points as the pandemic continues.
What does this result mean?
The seroprevalence survey results indicate a large proportion of the population is still susceptible and can get COVID, says Dr Prabhdeep Kaur, Scientist E and Deputy Director ICMR- National Institute of Epidemiology, who is heading a central team to Puducherry to assist the government.
“We detect only a fraction who are symptomatic and seek care”, she says.
Puducherry is still in the early phase of the epidemic and a lot of preparation is required as the virus is here to stay for a long time.
Preparation
ICMR has given several recommendations including decentralization of testing facility to health and wellness centres for surveillance, setting up dedicated COVID clinics, including using pulse oximeter for regular checking of patients to reduce fatalities, enhancing testing, an increase of oxygen beds, additional manpower among others.
However, some doctors opine that the survey is reflective of the July situation and that it is September already. Much water has flown under the bridge and is not comparable to today’s scenario.
Today's prevalence cannot be said from the survey that was done in August.
Today's prevalence of infection can be known by doing the survey two weeks later, said Dr Sonali Sarkar, Head, Department of Social and Preventive medicine, JIPMER.