St Ives in Cornwall, popular with surfers and art lovers, has found itself the unlikely focus of an Aids scare.

Up to 10 cases of HIV have been identified among people aged 20 to 50 in the past month. All were infected through heterosexual sex and the virus may have been acquired at any time over the past eight years, doctors said.

The news has stunned the town. The local population of 10,000 is swollen by tourists in summer, who come to visit the Tate gallery and to eat ice creams on its beaches. There is no significant drink or drug problem and only one club, the Isobar, located in its picturesque cobbled streets. "If it had been Plymouth or Penzance, I wouldn't have been surprised. But St Ives? It's bizarre," one resident, Caroline,said.

The West Cornwall Primary Care Trust declined to confirm the exact number of cases or explain how they had come to light, to protect patient confidentiality. The outbreak is thought to have been triggered by a single HIV carrier who had sex with a number of people.

The virus has since been transmitted on as the group of those infected includes men and women.

Dr David Miles, the director of public health, urged anyone who had unprotected sex outside a long-term relationship to go for an Aids test. It had not been possible to identify and trace the previous sexual partners of all those infected, he said.

Speaking at a press conference called by the health trust yesterday, he said: "It is within the last month that we have become aware of a number of cases.

"All those involved came from the St Ives area. Most people from the town will not be affected, or exposed to risk, because they are in long-term, stable relationships. But there are people who may have engaged in unprotected sex activities.

"If anyone considers that they have been at risk, then we can offer them advice and testing."

Before the outbreak, between 70 and 80 people had been diagnosed with HIV in the St Ives area since 1990. "This is a number of cases over a short time," Dr Miles said. "We can't say how they came to light, but there are general genito-urinary checks made that are common.

"We are not aware of any circumstances like this ever before in Cornwall."

There have been two previous clusters of HIV cases in Britain, spread through heterosexual sex. In Doncaster five women were infected in the 1990s by a nightclub bouncer who contracted the virus through drug use and claimed to have had sex with hundreds of women. A second cluster occurred in 2001 on the Isle of Man.

A spokeswoman for the Health Protection Agency said it was easier to identify clusters of HIV cases in small communities such as St Ives because they were likely to attend the same genito-urinary medicine clinic. "In urban areas, where people may go to any one of several clinics, it is more difficult to make links between them," she said.

The St Ives Liberal Democrat MP, Andrew George, said he feared a backlash against the resort after this outbreak.

He said: "I think it would have been better to say there have been cases in the west of Cornwall so that St Ives does not suffer any ill effects from this news.

"I don't think it will give the town a bad name but this situation does remind people of the risks they are taking if they don't use precautions."

A helpline has been set up by the health trust on 0845 850 9850.