While the threat of a bird flu pandemic continues to hang over the world, authorities in the United Kingdom now believe a second strain of avian flu -- previously considered of little human risk -- does indeed pose a real danger to people.

"When you have to hospitalize someone for respiratory illness in the U.K., where hospital beds are hard to allocate, then the person has a serious illness," said Jonathan Nguyen-Van-Tam, a senior lecturer at Public Health Laboratory Services in London.

"In this outbreak, we had four people who tested positive for H7 influenza strain, and three of them were hospitalized," he told United Press International. "One person was a candidate for intensive care before he finally came around.

"I think we need to reconsider the H7 strain on the basis of this outbreak," Nguyen-Van-Tam said in reporting how British authorities dealt with the disease encountered on small farms in Wales in the spring of this year.

He presented the report in a special late-breaker session at the Options for the Control of Influenza VI conference in Toronto, attended by more than 1,400 healthcare professionals.

Worldwide, the H5N1 strain of avian influenza, the so-called bird flu, has infected 313 humans and killed 191 of them. The H5N1 disease, seen sporadically since 1996 in Southeast Asia, Europe and Africa, does infect human beings with a strain that is not easy to combat, but so far, its ability to effectively spread from human to human has not occurred. However, health authorities worldwide are nervously watching for that possibility.

But while experts prepare for that grim possibility, a lesser-known relative of the H5N1 virus may be emerging as an equally formidable threat, based on what health authorities encountered recently on a handful of tiny chicken farms in Wales and northern England.

Authorities were alerted to an outbreak there at a smallholding -- a small farm often considered to be inefficient for profitable farming -- where 30 to 40 hens were kept. The farmer had purchased 10 new hens from a trader at the Chelford Market in England.

When the new hens began dying between May 1 and May 17, health authorities from both countries descended on the farm, testing the sick birds and determining that the birds had H7N2 disease.

Health officials also found illness in the farmer's wife and the farmer, a neighbor/visitor and her partner. Only the neighbor's partner tested positive for H7. The partner was not hospitalized but was treated with oseltamivir, sold as Roche's Tamiflu.

Tracking sales at the live poultry market through primitive sales records, Nguyen-Van-Tam said the health agency was led to another smallholding -- so small that the birds were being raised inside the home.

Ducklings purchased around May 7 began getting ill and dying on May 10. By May 15, the pregnant resident and a male resident were hospitalized with influenza-like illnesses and both later tested positive for H7 disease.

With two such cases on record, authorities tried to find the dealer who sold the sick animals but had problems finding him on his farm on the Llyn Peninsula in Wales. That was because, Nguyen-Van-Tam said, the farmer had been hospitalized for five days with an influenza-like illness. He also tested positive for H7 disease.

Authorities then discovered another outbreak among hens purchased at Chelford May 7 at another smallholding in St. Helens in northwest England. The surviving birds tested positive for H7. However, the resident who had an influenza-like illness and his 3-year-old grandson who developed a fever both tested negative for H7.

Over the course of the investigation, people who had contacts with the birds or with the patients were treated with oseltamivir. Eventually that amounted to 369 individuals, 31 of whom had contacts with the birds.

Nguyen-Van-Tam said 23 people developed some form of influenza-like symptoms during the course of the investigation and cleanup. Fourteen of those individuals had secondary contact, but none showed immediate exposure to H7 virus.

Blood testing to further determine if there was spread of the disease is under way. Nguyen-Van-Tam said the investigation was even more difficult because the outbreaks occurred during the seasonal influenza outbreak, making it difficult to determine with sophisticated testing if the patients were infected by the seasonal bug or by avian flu.

"This was a challenging incident," Nguyen-Van-Tam said, "complicated in terms of time and space. No evidence of person-to-person transmission has been found, but serology tests are awaited."

Nguyen-Van-Tam also reported on efforts to contain an H5N1 outbreak in February on a turkey farm in Suffolk, England.

That outbreak was contained in three days, during which authorities slaughtered 160,000 turkeys and treated 482 people who worked on the large poultry farm or were from public health offices engaged in capturing the turkeys and euthanizing them.

The people exposed to the birds were treated with oseltamivir, but no human cases of H5N1 occurred in that incident.