Two asymptomatic healthcare workers reinfected with Covid-19

Two healthcare workers at a Covid-19 unit in north India have been found to be reinfected with coronavirus weeks after the first infection. Remarkably both are asymptomatic.

Scientists who genomically tested samples from the first and second episodes of infection found that genetically distinct Sars-CoV-2 viruses were responsible for the two separate infections.

Both healthcare workers had tested positive as a result of routine surveillance.

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Dr Vinod Scaria of CSIR Institute of Genomics and Integrative Biology tweeted that: “Since the individuals were asymptomatic during both incidents and identified on regular surveillance, it suggests that asymptomatic reinfections could be an underreported entity.”

The paper which was published by Oxford University on Wednesday, reveals the two healthcare workers, a 25-year-old man and 28-year-old woman, both employed on Covid-19 duties at a tertiary hospital in north India, had first tested positive for the disease on May 5 and May 17, respectively.

Testing was done using the RT-PCR method. The researchers wrote: “Though both individuals were asymptomatic, they were hospitalised as per institutional policy on 5th May and 18th May, respectively.”

The male worker tested negative nine days later on May 13 while the woman staffer tested negative 11 days later on May 27.

Scientists say the pair resumed work at the hospital. However, routine surveillance testing found the male worker again positive for the disease on August 21 while the woman staffer tested positive on September 5. Both were again asymptomatic, but the data indicates the woman staffer had a high viral load. The Cycle Threshold (Ct) values were 36 for the man and 16.6 for the woman during the first episode and 28.16 and 16.92 for the second episode, respectively. (A number of 20 or below indicates higher viral load).

They were subsequently deemed as being clear of the disease on the 14th and sixth day, respectively.

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In a recent case of claimed reinfection in Bengaluru, researchers lacked nasopharyngeal or oropharyngeal swabs from the first episode of infection, which experts say make it difficult to prove reinfection.

However, in these two cases, the investigating scientists, from the Government Institute of Medical Sciences in Noida, CSIR Institute of Genomics and Integrative Biology (CSIR-IGIB) in New Delhi and the Academy of Scientific and Innovative Research (AcSIR) in Ghaziabad, had access to nasopharyngeal or oropharyngeal swabs collected from both the male and woman staffer during their first episode.

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“Genomes revealed 9 and 10 unique variant differences between the virus isolates from the two episodes of infection,” the scientists said.

They added that the virus found in the second episodes had a genetic variant (22882T>G) which they say may confer resistance to neutralising antibodies.