Mystery of British couple's death in Chiang Mai

Questions raised about safety of Thai city following spate of heart attacks officially blamed on virus

The mysterious deaths of up to seven tourists in the northern Thai city of Chiang Mai have baffled the authorities, casting doubts over the safety of the popular holiday destination.

A British couple, a 23-year-old New Zealander, and a Thai tour guide all died within 16 days in adjoining rooms at the three-star Downtown Inn in February. All four are believed to have died in remarkably similar circumstances, while three other cases have been speculatively linked to the phenomenon after displaying similar symptoms. Thai health authorities have blamed "toxic seaweed" for one of the deaths, but amid calls for a fresh investigation, one expert said that food poisoning was unlikely to be the cause.

Thai police have ruled out foul play and said there was no evidence that the deaths were linked. Health authorities said at least two were probably caused by food poisoning. The Governor of Chiang Mai, Panadda Disakul, said they were nothing more than a coincidence, according to news reports.

But David Mabey, professor of communicable diseases at the London School of Hygiene and Tropical Medicine, said that if the cases were a coincidence they would be a "remarkable" one. He described the deaths as "absolutely extraordinary" and said that food poisoning would "certainly not" be one of the first possible causes to spring to mind.

Richard Carter, the father of the dead New Zealand woman, Sarah Carter, said that he believes the deaths are linked and that the investigation into his daughter's death, which continues to focus on food poisoning, is "narrow-minded". Mr Carter has also claimed that the initial examination of the relevant hotel rooms consisted of little more than a "cursory sweep" and has demanded a fresh look at his daughter's case.

Ms Carter had been on a three-week holiday when she and her travel companions, Amanda Eliason, 24, and Emma Langlands, 23, were taken to hospital with symptoms of food poisoning. Ms Carter's condition deteriorated quickly and she died from myocarditis (swelling of the heart) on 6 February within hours of being admitted. Ms Eliason and Ms Langlands recovered.

George and Eileen Everitt, from Boston, Lincolnshire, were found dead in their room 13 days after Ms Carter died. Mrs Everitt, 74, was discovered lying on the bed and Mr Everitt, 78, was sitting on the floor with his head resting on the bed. Thai authorities said the couple had suffered heart attacks, also thought to be the result of myocarditis, just minutes apart. Their room was below Ms Carter's.

"They had no history of heart problems or any other problems," the couple's son, Stephen Everitt, told the New Zealand Herald. "They were active and healthy for their age and it has come as a total shock. And now they want me to believe they had heart attacks at the same time. It doesn't make sense."

A 47-year-old Thai woman named Waraporn Pungmahisiranon was the first to die in her hotel room on 3 February, but this only came to light when alarmed guests reported seeing a body wrapped in a sheet being carried down the hotel's fire escape.

Further possible cases include Canadian Bill Mah, 59, who did not stay at the Downtown Inn, but did use its pool. He died suddenly, complaining of severe chest pains, though the cause of his death remains unknown. Soraya Pandola, 33, an American woman, died on 11 January after being treated in hospital for food poisoning, and a French woman is believed to have died in similar circumstances.

Chiang Mai health authorities say eating "toxic seaweed" from a nearby night bazaar may have triggered Ms Carter's death, and traces of the Coxsackie B virus were found in samples taken from her body. The virus can cause stomach upsets and, in rare cases, heart damage. But Professor Mabey says it would be "unusual for so many people to get myocarditis from [Coxsackie B and other similar viruses] at the same time".

New Zealand's Foreign Minister, Murray McCully, has called for "closer scrutiny" of Ms Carter's death, prompting Thai authorities to ask the World Health Organisation for help with further tests. Britain's Foreign Office said it has no plans to call for further inquiries into the Everitts' deaths.

The Downtown Inn and the market remain open after brief police examinations. Vinai Julsiri, the acting manager of the Downtown Inn, told The Australian that speculation surrounding the deaths had been "really bad for business". He said: "There is nothing wrong or dangerous in our hotel."

Chiang Mai attracts up to two million tourists ever year. In March, Thailand's Bureau of Epidemiology said over 19,000 people were treated for food poisoning in the previous two months. Thailand's Department for Disease Control says "threats to the general public remain low or minimal".

But Mr Carter believes the investigations are not being conducted properly to save face, and to protect Chiang Mai's tourism industry. "With something so extremely dangerous, the investigation should be broadened to look at everything that is used in the hotel."