In four Mumbai healthcare workers confirmed to be reinfected with Covid-19, with a gap ranging from 19 to 65 days between both infections, researchers surprisingly found no antibodies produced after the first infection. A whole genome sequencing has found 39 mutations in the four cases of reinfections.
“This virus has branched itself. Our reference virus is the Wuhan genome. And multiple mutations have come out like new leaves from the same tree,” said Dr Rajesh Pandey, from Institute of Genomics and Integrative Biology, part of the team that did whole genome sequencing.
The findings have been published in a pre-print of Lancet Medical journal.
Reinfection here means a person infected with Covid-19 and recovered tests positive again for a mutated or same strain of the virus. From India, this is the largest group of reinfections studied. Three of the four are male doctors from Nair hospital and the fourth is a nurse in PD Hinduja hospital.
All the four have no other illness, and had no or mild symptoms, like sore throat or cough, for 2-5 days during their first infection. In the second infection, their symptoms intensified with fever, headache, and muscle pain for two days to three weeks. In one case plasma therapy was required. In all four cases, reinfection was due to mutated strain of Sars-CoV-2.
Pandey said they found one important mutation, D614G, in two patients. “Presence of this mutation can potentially lead to greater infectivity in patients and cause severe symptoms,” he said. He added that while it was early to comment, if mutations do happen fast and if D614G mutation is involved, vaccines may not be effective for all individuals.
Dr Jayanthi Shastri, head of microbiology at Nair hospital, said, “The surprise find in this genome sequencing was lack of antibody production in all four after the first round of infection. The virus is evolving but the mutations are still slow.” She added that mild symptoms may also not necessarily lead to production of antibodies against the infection.
Since whole genome sequencing requires RNA from both first and second infection, Shastri said a huge challenge was storage of RNA. “A lot of hospitals are not storing good quality RNA. And that can be a problem if reinfection occurs.” As head of microbiology, she has maintained RNA data of Covid-19 patients in the laboratory to study for future infections, she said.
The study has indicated the need for preventing infection risk and framing policy for healthcare workers even after the first infection.
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