Second-home owners and caravanners have been urged not to come to north Wales to self-isolate from coronavirus.
A GP said health services have been inundated by people with second homes in Gwynedd looking for medical care.
The area has more second homes than any county in Wales. Dr Eilir Hughes has called on the Welsh Government to class travelling to second homes and caravans as "non-essential travel".
The Welsh Government has declined to comment.
Dr Hughes, GP and leader of the Dwyfor Primary Care Cluster, said: "Services expect seasonal spikes during school holidays.
"We try our best to prepare our services for this increased demand but are currently seeing a surge in demand for medical advice and assessment.
"We have seen several patients coming to use their second homes to self-isolate and using primary care services where they are not registered.
"It really does place a great strain on our infrastructure and our services," he told Radio Wales Breakfast.
Dr Hughes is concerned that the NHS in the area does not have the resources to deal with an increase in the population.
New measures introduced by Prime Minister Boris Johnson on Monday urged people to avoid all unnecessary travel.
Now Dr Hughes wants the Welsh Government to issue the advice to people not to travel and to return to their primary homes.
"People are travelling from outside the area, and increasing the viral load in the community.
"We have evidence that a significant amount of people who own holiday homes and static caravans have decided to travel down under the impression they'd be safer here.
"We must also remember that the people travelling into the area are often retired, meaning they are likely to be of an age at a greater risk of Covid-19."
Two people have died in Wales after contracting the virus.
His calls have been echoed by Dwyfor Meirionydd MP Liz Saville Roberts who said she was "extremely concerned" by reports of people coming into the area.
"It is highly likely that the virus is already established in the population of Gwynedd, but the lack of testing means no cases have yet been recorded," she said.
"People who have holiday homes in the area are seeing maps of Gwynedd as being free of Coronavirus and deciding to relocate here."
EASY STEPS: How to keep safe