State health department to conduct sero-survey to detect community transmissionUpdated: Jun 19, 2020 23:27 IST
To detect the prevalence of SARS-CoV-2 virus in the city, the state health department has started conducting sero-survey by testing blood serum of a group of people from a community.
Gurugram, with 4136 cases, so far had witnessed the highest number of cases in Haryana. The sero-survey, officials said, will help them detect the community transmission of the disease, if any.
At least 450 people in the city will be covered under the survey. Along with Gurugram, four other affected districts — Faridabad, Ambala, Panchkula and Sonepat — will also be covered in the survey. Earlier, the Indian Council of Medical Research (ICMR) had conducted the sero-suvey in 75 districts across the country and found that less than one percent of the population — 0.73% — in the non-containment zone had contracted the virus.
“The sero-survey is being done in the state to estimate the proportion of population exposed to Covid-19 infection, including asymptomatic individuals. It is a process to check undetected community transmission. The survey will be conducted in the high-risk or vulnerable population zones, where people have been infected in the past and have now recovered and also those who tested negative for coronavirus,” said Rajeev Arora, additional chief secretary, health department.
Community transmission of a disease happens when the source of infection can no longer be traced, leading to difficulty in containing it. Gurugram has currently breached the 4,000 mark in Covid-19 cases, and going by future projections, the number can reach up to 9,000 by the end of June. According to Arora, depending upon the seroprevalence of infection, the state can plan appropriate healthcare interventions.
“The sero-survey includes IgG Enzyme Linked Immunosorbent Assay (ELISA) test. For the survey, five millilitre blood samples will be collected. The sample will be put in a machine, which will separate blood and plasma. The plasma is then used to detect antibodies developed against coronavirus in the body. The IgG test is not useful for detecting acute infection but indicates episodes of Covid-19 infections in the past.”
Studies show that the IgG antibodies start appearing after two weeks of the onset of infection. Even if the patient has recovered, antibodies last for several months. The IgG ELISA test is approved by the ICMR, for it has high sensitivity and specificity.
The state has provided required kits to five districts. Since it is a survey, only limited number of kits have been provided. Ambala and Panchkula have got two kits each, while Faridabad, Gurugram and Sonipat has got five kits each. Each kit can test at least 90 samples, which can be tested together in a single run of two and a half hours.
“At least 50% of the kit will be used on already confirmed positive patients, having history of confirmation in the last two weeks. The remaining will be used on those who were confirmed negative,” said Arora, adding that district -level team will collect 30 samples per day, maintaining rural-urban ratio.
For the survey,samples will be collected from people having co-morbidity issues, from containment zones, health care workers, security and police personnel, rural population after reverse migration, labourers, farmers, staff in government agencies, among others, as per ICMR guidelines. The Haryana government has added few other sections of community — like pre-operative patients and pregnant women residing in containment zones who are likely to deliver in a week, and all elderly vulnerable population living in containment zones.