From among 868 deaths in the state, 23 were below 30 years old. (PTI Photo)

RANGING FROM a silent infection to a lethal disease, the SARS-CoV-2 virus has shown immense clinical variability. Scientists and immunologists across the world are exploring the question if it is possible that some are genetically resistant to the virus and, hence, do not get critically ill. In India, experts from Mumbai hospitals have submitted a study proposal to Indian Council of Medical Research (ICMR).

Dr Zarir Udwadia, noted pulmonologist at Hinduja hospital, Mumbai, told The Indian Express that they were keen on understanding why some young, but otherwise healthy, patients get critically ill or die of Covid-19. “We have planned a study by doing a genetic analysis of this specific group of people aged below 50 and who do not have any co-morbid health conditions and their families,” Dr Udwadia said.

Dr Mukesh Desai, principal investigator of the proposed study and chief immunologist at Wadia hospital in Mumbai, said a global effort had been underway since one-and-a-half months to understand and identify if there was a genetic defect in these patients without any co-morbid conditions, who at a young age got a severe form of Covid-19.

Dr Jean-Laurent Casanova, professor at Rockefeller University, along with Helen Su at National Institute of Allergy and Infectious Diseases are leading an international project – the Covid Human Genetic Effort – to comb through the genomes of many Covid-19 outliers in search of any rare gene variant that may explain the body’s insufficient response to the infection.

“Why would the spouse of a patient already ill for days and now in intensive care remain not only healthy but seronegative? How could a healthcare worker treating contagious Covid-19 patients with insufficient protection remain healthy and seronegative? If such individuals also test negative for T-cell responses to SARS-CoV-2, it is plausible that some are genetically resistant to the virus,” Dr Casanova, along with other co-authors, writes in the commentary in the peer-reviewed scientific journal Cell.

Dr Casanova said the Covid Human Genetic Effort proposed that previously healthy and young patients with severe Covid-19 carried causal genetic variants. “Why are previously healthy children, adolescents, young, or middle-aged adults being admitted to intensive care for respiratory failure due to Covid-19? Why would a 40-year-old man, who completed a marathon in October 2019, find himself intubated and ventilated for Covid-19 respiratory failure in April 2020,” Prof Casanova asked.

Explaining further, Dr Desai said immunologists had worked on the hypothesis if anyone exposed to the infectious agent and landed with severe problems, then the concept was she must have something wrong with the immune system due to which her body was overreacted or underreacted to the infection.

From among 868 deaths in the state, 23 were below 30 years old. “Applying the same principal to Covid-19, we want to understand why young people who have no risk factors land up with severe Covid pneumonia or new auto-inflammatory multisystem disorders or neurological problems,” Dr Desai said, adding that they wanted to join the international effort and had applied for grant at the ICMR.

“We want to involve as many hospitals as possible and, initially, will study 100 patients and their families,” Dr Desai added.