A couple of teams of disease experts have converged on Saudi Arabia, hoping to find the source of a new virus from the SARS family.

Experts from the World Health Organization and the Center for Infection and Immunity at Columbia University in New York are in Riyadh on the invitation of the Saudi government, a senior health ministry official confirmed Wednesday.

The Columbia team includes virologist Dr. Ian Lipkin, who was described as "the world's most celebrated virus hunter" by Discover magazine in a profile earlier this year. It also includes two experts from EcoHealth, a New York City-based international organization for ecology and health.

A team from the U.S. Centers for Disease Control in Atlanta is also slated to arrive next week, though Dr. Ziad Memish, Saudi Arabia's deputy minister of health, said those plans may change if no new cases of the disease come to light in coming days.

"If we feel that there's a need, of course we'll continue with the mission," Memish said in an interview.

"If we feel that things are being covered, and things continue to be stable, we're not saying we would cancel the team, but maybe we would delay it. We will have to review things every day."

To date there have only been two confirmed cases of infection with the new coronavirus, in a man from Saudi Arabia and another from Qatar. The Saudi man died in June. The man from Qatar was sent by air ambulance to Britain, where he remains in serious condition in a hospital in London.

In both cases the disease triggered both severe respiratory illness and kidney failure.

With two cases from two countries and several months between them, finding the source of the new virus will be a challenge, said Dr. Donald Low, an infectious diseases expert from Toronto's Mount Sinai Hospital.

"I bet it would be pretty difficult. Otherwise the answer may have been obvious by now," said Low, who was one of the key figures in Toronto's fight against SARS in 2003.

The new virus is a member of the family of coronaviruses, a large group which infects animals, birds and humans. Several of the human coronaviruses cause mild respiratory illness — essentially colds.

But at the other end of the disease spectrum was the virus responsible for severe acute respiratory syndrome — SARS — which infected 8,422 people and killed 916 in late 2002 and 2003. That's a case fatality rate of nearly 11 per cent.

Possibility of outbreak during hajj in Mecca

The emergence of the new virus comes at an delicate time, with Muslims from around the world arriving in Saudi Arabia for hajj, the annual Islamic pilgrimage to Mecca.

It's estimated that three million people will take part in this year's hajj and Memish said half a million have already arrived in the country. This year's hajj starts on Oct. 24.

Concern over the possibility of an outbreak during hajj was one of the reasons why three outside groups of disease detectives were asked for assistance. But Memish said the lack of evidence of spread of the illness from the cases to their contacts and health-care workers is easing concerns.

As for the possible sources of the virus, it's thought that animals found in the region may harbour the pathogen. Camels and goats have been named as a couple of possible sources.

Memish was vague when asked if the man who died had contact with animals.

"We have some information, yes, but the information is not complete yet. Once the information is out, we will announce it," he said, adding the teams are looking at both animals and the Saudi man's environment.