People who test positive for coronavirus or are showing symptoms will now have to isolate for 10 days instead of seven, it has been announced.
The announcement was made in a joint statement by the UK Chief Medical Officers on Thursday.
They said they came to the decision after discovering new evidence that suggests that the virus has a "low but real possibility of infectiousness between seven and nine days after illness onset."
They stressed the importance of self-isolating when symptoms first appear as well as getting a test in order for contact tracing to take place.
In line with original Welsh Government advice, those who continue to suffer with symptoms, other than cough or loss of or change to sense of smell or taste, you must continue to self-isolate until you feel better.
This is because a cough or change to or loss of smell or taste can last for several weeks once the infection has gone
A joint statement from the UK's chief medical officers, Professor Chris Whitty (England), Dr Frank Atherton (Wales), Dr Gregor Smith (Scotland )and Dr Michael McBride (Northern Ireland) said: “In symptomatic people Covid-19 is most infectious just before, and for the first few days after, symptoms begin. It is very important people with symptoms self-isolate and get a test, which will allow contact tracing.
“Evidence, although still limited, has strengthened and shows that people with Covid who are mildly ill and are recovering have a low but real possibility of infectiousness between 7 and 9 days after illness onset.
“We have considered how best to target interventions to reduce risk to the general population and consider that at this point in the epidemic, with widespread and rapid testing available and considering the relaxation of other measures, it is now the correct balance of risk to extend the self-isolation period from seven to 10 days for those in the community who have symptoms or a positive test result.
“This will help provide additional protection to others in the community. This is particularly important to protect those who have been shielding and in advance of the autumn and winter when we may see increased community transmission.”
The decision was made based on "strengthened" evidence, which they described as "still limited" and was made in line with World Health Organisation guidance.
The chief medical officers for England, Wales, Scotland and Northern Ireland said that it is "now the correct balance of risk" to extend the isolation period for those who test positive or have symptoms to 10 days.
It comes as Prime Minister Boris Johnson said he was very worried about "signs of a second wave of coronavirus" in Europe after tourists returning from Spain were told to self-isolate for 14 days.
The new rules are for people showing signs of the virus, anyone waiting for a coronavirus test result to come back and anyone who tests positive for the virus.
According to the Welsh Government, if you receive a positive test you will be contacted by a contact tracer on behalf of the NHS Wales Test, Trace, Protect service.
During the self-isolation period, a person and everyone in their household must remain at home and not go to any public areas.
No one should go out, not even to buy food or essentials and any exercise should be done in the home.
