London, Sep 11 (IANS): Contrary to expectations, hospital cleaners are at the higher risk of getting the Covid-19 infection, compared to intensive care unit (ICU) clinicians, say researchers.

The study, published in the journal Thorax, revealed that infection risk was highest among cleaners, acute and general medicine clinicians, and those of Black, Asian and Minority Ethnic (BAME) backgrounds.

The researchers suggest that the type of personal protective equipment (PPE) worn may be key to these differences, which are likely to be relevant for any second surge in Covid-19 this winter.

"We presumed intensive care workers would be at highest risk... But workers in ICU are relatively well protected compared with other areas," said study author Alex Richter from the University Hospitals Birmingham NHS Foundation Trust (UHBFT) in the UK.

For the findings, the research team offered to test staff with no Covid-19 symptoms for both current (throat and nose swabs to detect antigen) and previous (blood test to detect antibodies) infection.

"We recruited 545 staff in 20 hours," Richter commented.

They were asked to report any illnesses consistent with Covid-19 that they had had in the previous four months.

Nearly 2.5 per cent staff with no symptoms tested positive for SARS-CoV-2, the virus responsible for Covid-19 infection. Of these, 38 per cent subsequently developed Covid-19 symptoms.

Around one in four for whom serum samples were available said they had previously had symptoms consistent with Covid-19 infection.

The findings showed that cleaners had the highest antibody positivity (seroprevalence)-- 34 per cent followed by clinicians working in acute medicine (33 per cent or general internal medicine 30 per cent.

The lowest seroprevalence was found among staff working in intensive care medicine 15 per cent, emergency medicine 13 per cent, and general surgery 13 per cent.

"This is an observational study, and not all participants provided all the information requested. Nor is it known whether symptomless infection among staff puts hospital patients at risk," the study authors wrote.

"However, our data would support the assessment of widespread healthcare worker testing, including track and trace, on viral transmission during future waves of a pandemic," they concluded.