The threat of re-infection due to COVID-19 virus, though not common, is real and can also be more severe than the first one, shows a study published by Indian researchers. The pre-print paper has been written by researchers associated with Kasturba Hospital for Infectious Disease, Mumbai, and International Centre for Genetic Engineering and Biotechnology and CSIR-Institute of Genomics and Integrative Biology (CSIR-IGIB), New Delhi.
The study analyses the cases of four Mumbai-based health care workers (HCWs) to conclude that in all four, the combination of the clinical findings, RT-PCR and whole-genome sequencing (WGS) analysis confirmed re-infection. "We identified four HCWs who had tested positive for SARS-CoV-2 RT-PCR in May or June 2020 and again tested positive by RT-PCR when they developed symptoms suggestive of COVID-19 in July," says the report.
It adds that Kasturba Hospital was the diagnostic laboratory that tested three of the HCWs whereas the fourth was tested at PD Hinduja Hospital. "... (it) came to our attention when her attending physician requested us to verify her samples. Based on the RT-PCR results and clinical presentation of the HCWs, we suspected re-infection with SARS-CoV-2. Upon confirmation of the RT-PCR findings, whole-genome sequencing was performed on the stored paired samples," the report elaborates.
It added that the genomic variations observed through whole-genome sequencing, coupled with clinical presentation, confirmed COVID-19 re-infections in healthcare workers. The findings emphasise the need to provide additional protection to the HCWs as they are more vulnerable to re-infection. "HCWs can get re-infected with SARS-CoV-2 with increased clinical severity in the second episode. SARS-CoV-2 re-infection risk in convalescent health-care workers should be addressed in health-care policymaking," say the researchers.
The WGS analysis of the virus from the first and second episode also reveals that there are distinct mutations amongst the viruses collected at different time points. "Patient A and B were part of the same clinical team and it is expected that the virus strains may be similar. However, genome analysis reveals the viruses belonged to different subclades with a distinct set of variations detected in the first episode, thereby hinting they might have been infected through different sources," the report adds.
The study also says that their follow-up samples revealed different sets of mutations, indicating the second episode were fresh acute infections and not a carryover of the previous infections. "What can also be hypothesised is the source of infection about these two cases, specifically, is that most probably their infections occurred from the existing circulating virus pool within the same region/time point as opposed to the case of Patient D where the viruses clustered in different subclades and exhibited a larger set of different mutations, clearly emphasising reinfection of new SARS-CoV-2 strains," it revealed.
In case of Patient C, interestingly, despite the short period within the two episodes, the genetic variations were quite different, implying possible re-infection and not virus-shedding from the first infection, the report said. The researchers concluded the frontline HCWs have more than threefold higher risk of SARS-CoV-2 infection than the general community. They also face critical PPE shortage while dealing with the highest caseloads.
"There is an ever-pressing need to protect HCWs from exposure to infection with appropriate PPEs, and convalescence may not necessarily imply immunity," the researchers pointed out.
Jayanthi Shastri, Swapneil Parikh, Sachee Agrawal, Nirjhar Chatterjee, Manish Pathak, Chetan Sharma, Akshay Kanakan, Vivekanand, Janani Srinivasa Vasudevan, Ranjeet Maurya, Saman Fatihi, Lipi Thukral, Anurag Agrawal, Lancelot Pinto, Rajesh Pandey, and Sujatha Sunil contributed to the research paper.
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