By Charlene Porter
Washington File Staff Writer

Washington – The United States and Canada are working closely to keep watch for the introduction of highly pathogenic avian influenza into North America, according to U.S. Secretary of the Interior Gale Norton.

With the rapid movement of this dangerous bird flu virus across Central Asia, Europe and into Africa over the last few months, U.S. officials have come to accept that the appearance of the H5N1 virus in North America is inevitable.

Even though the precise method of the disease’s spread is not fully understood, flocks of migratory birds are thought to be carriers of the virus, capable of infecting other forms of wildlife and domestic poultry. (See related article.)

The United States has announced a campaign to step up surveillance of migratory birds, which are expected to transport the disease out of East Asia, through the state of Alaska and into the Americas via identified flyways.

“Since Canada is situated between Alaska and [the continental United States],” Norton said in a March 24 White House webchat, “we’ve [the United States] been coordinating closely with wildlife and health officials there and will continue to work with them on this important effort.”

Given the seasonal movements of flocks from Asia through Alaska and into the Americas, Norton said it is possible that the virus could arrive in Alaska during the Northern Hemisphere spring, which began March 20.

Later in 2006, the virus could be transported further south during the autumnal migration.

ENHANCED SURVEILLANCE CAMPAIGN

The enhanced surveillance campaign announced by three top government officials March 20 calls for detection and investigation of sick birds, monitoring of healthy birds, and targeted sampling of fowl to ascertain how many birds might be carrying the H5N1 virus that has caused the deaths of hundreds of millions of birds since the epidemic began in late 2003. (See related article.)

With U.S. agencies on the verge of testing tens of thousands of wild birds, Norton was keen to point out that avian influenza viruses come in many forms and most of them are benign.

“It is quite possible that we could have dozens of H5N1 reports [from forthcoming wild bird tests], with none turning out to be the highly pathogenic variety,” Norton said. “These low pathogenic viruses do not even cause particular problems for birds and are not relevant to human influenza concerns.”

The U.S. secretary of the interior also reminded her audience that H5N1 is an animal disease, and the appearance of the virus in a given locale does not mean that an influenza outbreak among humans is imminent.

The virulent nature of the strain of influenza does make health officials worry about the development of a human flu pandemic.

NEARLY 200 HUMAN INFECTIONS IN PAST TWO YEARS

The virus has infected close to 200 people over the last two years, and killed 105 humans, the most recent deaths reported from China and Cambodia, according to World Health Organization statements of March 24.

Virtually all those infections occurred through direct contact with sick birds, but if the virus mutates to become contagious among humans, widespread illness and death could occur.

The human cases detected so far in eight nations show no evidence that the virus has developed that capability.

Norton also tried to quell the misperception that detection of H5N1 in wild birds poses an immediate threat to human health.

“There are no documented cases of wild birds directly transmitting avian influenza to people,” Norton said.

Responding to a concerned participant in the webchat, Norton said the risk of disease exposure to hunters is thought to be low, but possible.

She urged hunters to practice good hygiene in handling and cleaning wild game.

A transcript of Norton’s webchat is available on the White House Web site.

For additional information on the disease and efforts to combat it, see Bird Flu (Avian Influenza).