ALMOST one in five staff members at an Irish hospital were found to have coronavirus antibodies.
The study, which was carried out at Tallaght University Hospital between mid-July and mid-October, surveyed 1,200 people.
This equates to around one-third of all staff working there.
18% of those who took part in the test showed that they had coronavirus antibodies.
Just 12% of those involved in the survey had previously tested positive for Covid-19 - alarmingly suggesting that a significant number of staff there unknowingly contracted coronavirus, and even worse, may have unknowingly spread it.
The study was open to all hospital staff including doctors, nurses, lab assistants, social workers, cleaning staff and electricians.
For staff working in more direct contact with patients, the detection rate was 20% and the rate was 13% for people with less direct patient contact.
Commenting on the study, consultant microbiologist Dr Anna Rose Prior said the results show that a "high proportion of Covid infection in healthcare workers goes undetected."
Statistics coming from the Health Protection Surveillance Centre showed that healthcare workers account for 21.8% of all coronavirus cases in Ireland.
A HSE study on Covid-19 antibodies in Irish people with results up to mid-July found that 1.7% of people had Covid-19 antibodies.