A significant percentage of novel coronavirus infection (COVID-19) cases in India could be that of people without any history of contact with a known case or international travel, an analysis carried out by the Indian Council of Medical Research (ICMR) suggests.
The assumption is based on the results of an ongoing COVID-19 sentinel surveillance programme ICMR has been undertaking in parallel to the regular COVID-19 diagnostic testing, ever since the first coronavirus infection got reported in India.
WHO defines sentinel surveillance as a system where pre-determined reporting units, with a high probability of seeing cases of the disease in question, good laboratory facilities and experienced well-qualified staff, identify and notify on certain diseases. It is used when high-quality data are needed about a particular disease that cannot be obtained through a passive system. India has a Virus Research and Diagnostic Laboratory Network (VRDLN) for this purpose.
The sentinel surveillance project of ICMR saw 104 samples - from among 5911 samples of severe acute respiratory illness (SARI) patients admitted at 41 sentinel sites that are part of VRDLN - testing positive for COVID-19. The samples were collected from February 15, 2020 onwards across 52 districts in 20 states and union territories and 40 positive cases (39.2 percent of COVID-19 cases) did not report any history of contact with a known case or international travel.
The findings, published in the Indian Journal of Medical Research, reveals that COVID-19 positivity among SARI patients increased from 0 per cent before March 14, to 2.6 per cent by April 2, 2020. "In 15 Indian states, more than one per cent of SARI patients were COVID-19 positive. About a third of COVID-19 positive SARI cases did not have any history of contact with laboratory-confirmed case or international travel, and such cases were reported from 36 Indian districts in 15 States. These districts need to be prioritised to target COVID-19 containment activities," the report said.
COVID-19 cases among SARI patients were detected from 52 districts in 20 States. Majority of the SARI patients were tested from Gujarat (792), Tamil Nadu (577), Maharashtra (553) and Kerala (502) with COVID-19 positivity of 1.6, 0.9, 3.8 and 0.2 per cent, respectively (Table III). COVID-19 positive SARI patients were detected from eight districts in Maharashtra, six in West Bengal and five each in Tamil Nadu and Delhi, the report said.
Researchers at ICMR concluded that COVID-19 containment activities need to be targeted in districts reporting COVID-19 cases among SARI patients. They also called for intensifying sentinel surveillance for COVID-19 among SARI patients may be an efficient tool to effectively use resources towards containment and mitigation efforts.
The VRDLN system was developed in India after the country witnessed acute outbreaks or threats of infiltration of new or exotic viruses such as Nipah virus, SARS-CoV , Avian Influenza H5N1, chikungunya, Ebola, Zika, Yellow fever virus and MERS-CoV (Middle East Respiratory Syndrome-coronavirus) in the recent years.