India is not only dealing with a heavy case burden of close to one lakh new cases COVID-19 daily, but a few people are also testing positive again for the mutant strains of SARS-CoV-2. To ensure that it is actually a case of reinfection and not traces of the existing infection, the Indian Council of Medical Research has developed an easy-to-use epidemiological definition for COVID-19 reinfection.
According to the ICMR, if a person tests positive after testing negative and recovering from a previous bout of COVID-19 within a period of 102 days, the epidemiological definition will suggest that this is a case of reinfection. The samples will also be sent for genomic sequencing. If the sequencing points out that the person has been infected by a mutant strain of SARS-CoV-2, the laboratory definition of re-infection will be fulfilled.
At the weekly COVID-19 press briefing, Dr. Balrama Bhargava, Director General, ICMR, even stated that reinfections are currently not a cause for worry. "We have come up with a definition that has been approved and accepted. Even though the prevalence of reinfection is less than 1% so far, it is better to have a definition for it," Bhargava stated.
While the American and European Centres for Disease Control and Prevention mandate genomic sequencing to confirm a case of reinfection, the American CDC keeps a window of 90 days. The basis of choosing 90 days are studies showing prolonged viral shedding up to 82 days but there have been no prospective studies suggesting the same. Genomic sequencing is undertaken as the virus has been mutating and there has been an emergence of several mutant strains across the world.
Publishing their study in the Cambridge journal Epidemiology & Infection, the ICMR said its objective to develop an epidemiological definition for reinfection through a literature review of viral kinetics. As genetic mapping can be resource intensive, the ICMR decided to come up with an epidemiological definition. Defining and studying reinfection, although its prevalence is low, is important to establish surveillance systems, the study called 'SAR-CoV-2 reinfection: development of an epidemiological definition from India', says.
Around 4.5% of the totally infected people in country are reported to have been reinfected by SARS-CoV-2, according to this study. The researchers came to the 102 number after going through several published studies that spoke about viral shedding and reinfection across the world.
The study came to this definition after telephonically interviewing 38 participants who could be contacted from the 58 participants who fulfilled their case definition. Health workers are at a higher risk of developing reinfection as the study shows since 31.6% of their participants were health workers.
The patients were largely asymptomatic the first time around. However, they showed symptoms in the second episode. Even though there was no statistically significant difference in the people showing severe symptoms or milder symptoms, 12 out of 18 people who were asymptomatic in the first episode showed symptoms when reinfected. From the 20 who showed symptoms both the times, six reported more severe symptoms, six reported milder symptoms while eight reported no difference in their symptoms. It is to be noted that although several showed symptoms, the cycle threshold value (Ct) used for measuring severity of the disease, were lower when reinfected.