New Delhi: A new study from the Indian Council of Medical Research (ICMR) suggests that community transmission of COVID-19 has begun in several parts of India. The study found that out of 5,911 people across the country suffering from severe acute respiratory infections (SARI) since February, 104 were positive for COVID-19. Forty of these cases had neither a history of international travel, nor any contact with others who had COVID-19. In another 59 cases, public-health officials don’t yet know how the patients contracted the viral illness. Together, these data suggest that COVID-19 has spread beyond travellers and their close contacts in parts of India, making contact-tracing infeasible here.
The study, published in the Indian Journal of Medical Research, is the first time that ICMR has released comprehensive data on its testing among SARI patients, which began on February 15. Testing for COVID-19 in people who have no travel history is a valuable tool for nations to gauge the extent of community transmission. And the data, which comes from 41 laboratories across the country, shows a steady rise in COVID-19 positive cases in the last few weeks. While there were 0 positive cases in the week starting February 15, this percentage rose to 1.9% two weeks later. Then, between March 29 and April 2, 2.6% of all tested SARI patients turned out to be positive for the SARS-COV-2 virus.
The jump in the week ended April 2 may have to do with the fact that India began testing all SARI patients on March 20, instead of just a small random sample of cases coming to each of the sentinel labs.
Despite this rising trend of COVID-19 positivity, ICMR has been denying community transmission for a while. “Tests on SARI patients show no community transmission,” the agency told NDTV two weeks ago. However, it is critical to note that as on today, the World Health Organisation (WHO) hasn’t classified any country, including the badly-hit Italy, as undergoing community transmission. This may be because the WHO defines community transmission as a situation in which a large number of cases have no travel history. But the WHO doesn’t explain what “large” means. So, ICMR may continue to insist that India is seeing only local transmission, depending on whether it considers 40 to be a large enough number or not.
The new study also highlighted how widespread COVID-19 cases are in India today. About a third of all positive SARI patients were from 36 districts of 15 states. Some of the worst affected districts included eight in Maharashtra, six in West Bengal and five each in Tamil Nadu and Delhi. In 15 states, more than 1% of SARI patients were COVID-19 positive. The authors recommend that these districts be prioritised for COVID-19 containment activities.
Nearly 84% of SARI patients with COVID-19 in the study were men. Meanwhile, 82% of the patients (from all genders) were older than 40 years.
The study also suggests that older people are more likely to contract COVID-19, a phenomenon seen in other parts of the world too. While 25% of the SARI patients were aged between 20 and 29 years, just nine of them had COVID-19. In contrast, among those aged 50-69 years (constituting 23% of the total patients), 57 tested positive.
Limitations of the study
The study has several limitations, however. For example, it isn’t known what proportion of all hospitalised SARI patients were tested by each of the 41 sentinel laboratories.
“This proportion is expected to be lower during initial weeks of surveillance. However, with the expansion of the testing criteria to include all SARI patients, it is assumed that majority of SARI patients hospitalised in these facilities would have been tested for COVID-19,” the authors say.
Further, most of the sentinel hospitals which tested for COVID-1 are state-run and located in urban areas. This means that the study would not be able to pick up on community transmission in rural areas, if it is happening. Also, the fact that private labs and hospitals may not be sending their SARI samples to government-tun testing sites is a blind-spot.
Finally, the authors say the study could have missed some COVID-19 positive SARI patients, because the test used, called the reverse-transcriptase real-time polymerase chain reaction (RT-PCR), which looks for viral nucleic acids in patient samples, can return false negatives. Testing for SARS-COV-2 antibodies, in addition to nucleic acids, could have thrown up more positive cases, the authors said.
India’s COVID-19 testing strategy
On Thursday, the ICMR revised its testing strategy, incorporating the recommendations made by the study. The testing so far was targeted at symptomatic people who had international travel history, symptomatic contacts of laboratory-confirmed COVID-19 patients, symptomatic healthcare workers, and all SARI cases. Now, India will include people suffering from influenza-like illnesses in all the hotspots identified in the country. All asymptomatic direct and high-risk contacts of a confirmed COVID-19 patient will also be tested once, between day 5 and day 14 of coming in contact, according to the new strategy.