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10 March 2005

United States, Thailand Keeping Watch for Bird Flu in Humans

Disease surveillance programs look for virus to appear in people

By Charlene Porter
Washington File Staff Writer

Washington – International health officials are worried about the chance that a virulent strain of bird flu circulating among the Asian poultry population might mutate into a form that could widely infect humans, leading to a global epidemic.

The first clues that such an epidemic is about to begin will be discovered through active surveillance programs to analyze viral strains that are infecting people who come down with flu or pneumonia symptoms.

Scientists from the U.S. Centers for Disease Control and Prevention (CDC) are working with Thailand’s Ministry of Public Health (MOPH) to conduct some of the most thorough disease surveillance programs in the entire region.

CDC’s International Emerging Infections Program (IEIP) in Bangkok has been conducting disease surveillance to better understand pneumonia in Thailand.  IEIP Director Dr. Scott Dowell told the Washington File in a March 7 phone interview that bird flu in humans shows symptoms similar to pneumonia.  "So the ability to pick up pneumonia, and describe pneumonia, gives us a leg up on picking up cases of bird flu and understanding how we detect them when they come into humans,” he said.

Bird flu has stricken flocks widely across the region, with eight nations detecting the highly infectious avian influenza virus known as H5N1. The World Health Organization reports 55 laboratory-confirmed cases occurring in humans in Thailand, Vietnam and Cambodia, with 42 deaths -- an unusually high death rate for influenza.

In almost all these cases, health officials have determined that the individuals became sick because of exposure to infected birds. The virus has not become easily transmissible from human to human, according to current findings, but with the virus circulating so widely, experts say it could mutate into another form at any time.

“When that first starts to happen, person-to-person spread, we want to be darn sure that we know about it as early as possible,” said Dowell.

The Thai MOPH has a nationwide surveillance system in place, Dowell said, supported by a health care infrastructure that is well qualified to conduct the testing and diagnosis necessary to ascertain what viral strain has infected a sick person. A nationwide alert is circulating among medical personnel all over the country to keep watch for the symptoms of the disease as they have appeared in humans so far.

In addition, MOPH is sending teams into the community on a regular basis to look for cases of respiratory illness that were not serious enough to send the patient to a hospital.

CDC began its emerging infection program in Thailand in 2001 to contend with precisely this type of situation, Dowell said. The program has helped improve diagnostic capabilities in the Thai health care system to some degree, Dowell said, even as he praised the competence and availability of medical services throughout the country.

“But that’s going to be different in neighboring countries, in the much poorer countries,” the IEIP director said. “It’s going to be more difficult to pick up early cases of bird flu if they occur there.”

IEIP has conducted regional conferences, training laboratory staff from other nations of Southeast Asia in diagnostic testing so there is capability in larger, national laboratories throughout the region. If the H5N1 mutates into a human transmissible form in a rural corner of Southeast Asia, that could be the beginning of a serious public health problem.

“There is definitely always the concern that the first big human-to-human spread will occur in a place where we’re not as ready as in Thailand,” Dowell said.

In the not-so-distant past, this type of outbreak was thought to be impossible. Avian influenza did not occur in humans, according to the old dogma.

A 1997 outbreak in Hong Kong became the first case in which transmission occurred directly from birds to humans. The old wisdom was proven false and since then outbreaks of bird flu in humans have occurred elsewhere in Asia, Europe and North America.