New Delhi: The government is going to initiate a serosurvey to monitor the prevalence of coronavirus infection at the district level. According to a report by PTI, the Union Health Ministry said on Monday that two government research bodies are in the process of initiating a population-based serosurvey to monitor the trend in the prevalence of the infection at the district level.

What is a serosurvey?

In a serosurvey the blood serum of a group of individuals is tested to see if there is a presence of antibodies against infection.  This type of survey has been utilised for other diseases such as measles, rubella, polio, etc and is especially used to check the effectiveness of vaccination programmes. According to a document regarding the serosurvey in the Health Ministry website, in the case of the novel coronavirus, this survey will help to evaluate the way the virus is spreading.

How will it be done?

The document that elucidates the protocol for the survey sates that The Indian Council of Medical Research (ICMR) and the National Centre for Disease Control will collaborate with key stakeholders for the survey at 10 health facilities (6 public and 4 private).

For the survey, the demographic has been divided into low-risk populations such as Outpatient attendees and pregnant women and high-risk populations such as health care workers.

The document states that throat/nasal swabs will be collected for RT-PCR tests and samples would be tested in a one-time pool of 25. The result of this pool test will be used only for surveillance purposes and not for a diagnosis.

It is also specified that In addition to throat/nasal swabs, blood samples will also be collected for detecting IgG antibodies for ELISA testing. According to the protocols for serosurvey, ‘In subsequent rounds, IgG ELISA based testing of serum samples will replace RTPCR based testing for surveillance purposes.”

Data from the survey

Data on demographic characteristics will be collected on a specifically designed standard data collection form. The data which is collected will be analyzed locally for action using standard indicator formats. Indicators for person, place, time, and trend analysis will be made. Data collation and dissemination will take place as decided jointly by ICMR and the department of health and family welfare. The document added that "This surveillance will be in addition to the routine testing as per current testing guidelines."

The survey will include 200 samples a week and 800 samples per month. At least 100 samples per week and 400 per month of healthcare workers from selected districts would be tested.

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