Washington – More than 13,000 wild migratory birds have been tested in the United States without detection of the highly pathogenic avian influenza strain that has caused the deaths of more than 200 million birds worldwide.

The U.S. departments of Agriculture (USDA) and the Interior (USDOI) announced the progress of the expanded bird-testing program August 29, achieved through cooperation between federal, state and nongovernmental nature organizations.

In mid-August, the secretaries of the two agencies visited sites in Alaska, where most of the sampling has been conducted because of the northernmost state’s position on the bird migration flyways from Asia to the Western Hemisphere, according to a USDA news release.

“Guided by the national and wild bird surveillance and early detection plan,” said Secretary of the Interior Dirk Kempthorne, “our collaborative efforts have comprehensively sampled and tested high-priority species throughout Alaska.”

The surveillance and detection plan was released in March as part of U.S. efforts to prepare for a potential flu pandemic.  (See related article.)

The threat of a pandemic seemed high in the early months of the year, as the dangerous H5N1 virus started appearing in increasing numbers of countries in Central Asia, Europe, the Middle East and Africa.

The virus has killed more than 140 people in 10 countries since 2003. This strain of flu virus only rarely has infected humans, so no natural immunity will protect those infected.

The H5N1 strain in its current form is not easily transmitted among individuals. If it mutates and acquires the ability, health authorities warn of disease outbreaks of pandemic proportions.

The U.S. wild bird testing campaign has focused on 26 target species that are thought to be especially vulnerable to exposure because of their migratory patterns and habitats.

Of the 13,000 birds sampled, more than 110 birds have tested positive for some form of avian influenza, but this is a predictable finding, according to USDA, given that 144 subtypes of bird flu viruses circulate among wild bird species, often without adverse effect.

As autumn draws near in the Northern Hemisphere, migrating birds will be moving great distances again, and sampling campaigns will be expanded in states in the U.S. southern region.

Migratory birds are just one of the means by which H5N1 or any dangerous microbes might enter a country.

Poor biosafety practices in international travel, and legal and illegal commerce in poultry, wildlife and wildlife products are other pathways for disease to be carried from nation to nation. (See related article.)

CONTAINING A PANDEMIC

Controlling the disease in the animal population and watching for possible crossover into the human population are some of the most intense activities now under way in the global effort to prevent the emergence of pandemic influenza.

But health officials also are planning for the failure of containment and the emergence of a pandemic in the human population by devising plans to cope with widespread disease.

While anti-viral medications and trial vaccines have been successful in treating or preventing the serious respiratory illness that H5N1 has caused in more than 240 people worldwide, there is no certainty that these solutions would be effective or adequately available if a pandemic is sparked by a mutated form of H5N1.

A joint research team involving U.S. military biological scientists and a private U.S. research firm is finding some clues on alternate responses to cope with widespread serious disease.

Blood transfusions from people who had recovered from influenza in the epidemic of 1918 given to others still vulnerable to disease may have reduced the risk of death and improved symptoms of hospitalized patients, according to research to be published in the October edition of the Annals of Internal Medicine.

H5N1 is related to the virus that caused the worst influenza pandemic in recent history, the 1918-1920 Spanish flu that killed between 20 million and 100 million people.

The researchers pored over medical literature from the period and found eight limited studies that seemed to show that transfusion therapy provided some benefit.

The researchers predict that one person recovered from H5N1 illness could provide “a weekly volume of plasma sufficient to treat multiple patients with H5N1 influenza.”

They acknowledge the limitations of the 80-year-old research, on which they based their conclusions, and call for experts to study the possibility of plasma therapy and consider recommendations on a treatment regimen.

See Bird Flu (Avian Influenza) for ongoing coverage.

The blood transfusion research study, “Convalescent Blood Products for Spanish Influenza Pneumonia,” is available on a Web site of the American College of Physicians.