People who have tested positive for Covid-19 or have symptoms will now have to self-isolate for 10 days, rather than seven, the UK government has said.

The decision by the chief medical officers is a response to concern at the rising numbers of infections in Europe and is not based on new evidence, it has emerged.

Scientists have known for some time that a small number of individuals will remain infectious for as long as seven to nine days, even though most people will no longer transmit the virus after a few days of illness.

The change brings the UK into line with the World Health Organization’s recommendation for 10 days’ self-isolation, along with a number of other countries including Australia and Switzerland.

In a statement, the four chief medical officers for England, Scotland, Wales and 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-19 who are mildly ill and are recovering have a low but real possibility of infectiousness between seven and nine 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.”