About 10% of NHS staff in Wales are currently off sick or absent.
NHS Wales Chief Executive Andrew Goodall said that number is around two times higher than what they would expect "at this stage."
The number of frontline staff who had been tested for the virus is more than 1,500.
Speaking at the Welsh Government's daily briefing on coronavirus, Dr Goodall stressed the importance of having the right "testing mechanisms" in place so that healthcare staff with Covid-19 could be identified.
On Wednesday, Wales saw its highest amount of coronavirus-related deaths within the space of one day.
Watch the press conference here:
Dr Goodall said they are looking at increasing testing of frontline staff. At the moment, around 200 staff are tested each day.
He also emphasised that the amount of tests carried out in total every day is around 1,000. The hope is to increase that to 1,100 per day by the end of this week.
Speaking on the number of people with coronavirus in our hospitals, Dr Goodall said there were currently 573 people in NHS beds with confirmed cases and a further 393 with suspected cases.
He added that just over half of critical care beds in Wales were unoccupied.
At the briefing, Dr Goodall also said the number of A&E attendances had reduced dramatically, falling by 60% over the past two weeks.
He also announced that he expects new guidelines for on the use of PPE to be released.
Coronavirus: Everything you need to know: