Wales’ chief medical officer has warned “there is a long way to go” in the fight against coronavirus, adding that moving forward would be “extraordinarily difficult”.

Dr Frank Atherton said that while a peak of Covid-19 cases had come much earlier due to lockdown measures, there remained worries about a continued spread in hospitals and care homes.

On Thursday, Public Health Wales announced a further 22 people had died after testing positive for the virus in Wales, taking the total number of deaths to 908, while the number of confirmed cases grew by 183 to a total of 9,812.

Dr Atherton told the virtual meeting of the Welsh Assembly’s health committee that the reproduction rate of the virus – the number of new cases linked to a single individual – was now less than one in Wales, meaning that lockdown measures were working.

But the meeting heard that there was little “headroom” for an increase in infections that were likely if such measures were significantly lifted.

“We’re not out of this yet and we have a long way to go,” Dr Atherton said.

“This virus has many surprises and they pop up on a daily basis.

“Getting out of this predicament is extraordinarily difficult.

“It is one that we don’t do alone, we do in concert with our colleagues across the rest of the UK, and we need to continue learning from others.”

Dr Atherton said the lockdown restrictions had been successful in ensuring the NHS was not overwhelmed but warned that Wales was “not out of the woods yet”.

He told the meeting that the “sting in the tail” was that completely suppressing transmission risked a second or possibly third wave of the virus.

Dr Rob Orford, Wales’ chief scientific adviser for health, told the meeting that infection levels would increase if lockdown restrictions were significantly lifted.

The committee also heard health minister Vaughan Gething question the change in testing policy in England, after it decided to extend tests to care home staff and residents regardless of whether they had Covid-19 symptoms, something the Welsh Government has refused to follow.

He said: “I don’t understand the rationale in terms of how it keeps the public safer and how it saves more lives for the way that the testing policy has been changed in England but I’m not responsible for those policy choices.

“Just testing every care home resident doesn’t automatically make them safer because the test tells you whether you had coronavirus at the point in time when the test was undertaken, not whether you could get it the next day.”

Dr Atherton later defended Wales’ decision not to follow England’s lead, telling the Welsh Government’s daily briefing that the UK Government’s coronavirus scientific advisory group for emergencies (Sage) had not yet examined the benefits of doing so.

Asked if England’s decision was “political”, Dr Atherton said: “We’re still trying to reach across to England to understand the exact rationale for the changes they’ve made in various categories, given they’ve made a number of changes all at the same time.

“Our approach in Wales has consistently been to follow the science, and the science is the science.”

He added: “I rely on Sage, and Sage has not to my knowledge looked at the question of whether testing of asymptomatic individuals gives us benefits in terms of viral transmission.

“It’s a question I’ve asked our chief science officer to feed into the Sage process so that we get a better view on that.”

Dr Atherton said the spread of the virus in care homes as well as hospitals remained a “worry”, and that he had outlined steps which needed to be taken to First Minister Mark Drakeford, including improving surveillance of the spread, improving tracking and tracing, and learning from other countries.

On care homes, he said: “We do need to do far more. We need to be guided by the evidence.”