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Homeland Security

Brooks lab helping detect avian flu

by Rudy Purificato
311th Human Systems Wing


11/10/2005 - BROOKS CITY-BASE, Texas (AFPN) -- An epidemiology laboratory here is working to develop more effective and timely methods for detecting the deadly avian flu virus.

The Air Force Institute for Operational Health's epidemiology division is doing the research. The effort will support a worldwide Air Force surveillance program designed to safeguard American servicemembers from a potential outbreak.

The division is at the forefront of an Air Force initiative to create more reliable and faster testing procedures for H5N1, the influenza virus that scientists believe has spread from birds to humans across three continents.

"We're developing (DNA testing) to rapidly screen for avian flu," said molecular biologist Maj. David Eddington, the division's microbiology chief.

This year Air Force scientists began the process of developing new technology to detect avian flu. The new assay -- DNA testing -- uses polymerase chain reaction, or PCR, technology. This is an easy method for generating unlimited copies of any fragment of DNA.

Additionally, the organization is capable of performing molecular sequencing of the viral genome which helps detect mutations, the major said.

Since first appearing in Asian poultry in 1997, the highly pathogenic avian influenza, its scientific name, has mostly killed people who have been in direct contact with domesticated fowl. The deadly respiratory strain has become zoonotic (jumping from non-human host to people), leading to the first reported human death in 1997 in Hong Kong.

Scientists fear that its transmission between humans could trigger a pandemic. Such was the case in 1918, with the Spanish flu; in 1957’s Asian flu; and 1968’s Hong Kong flu. These outbreaks killed millions worldwide.

To cause a pandemic, it would have to mutate. For avian flu to become pandemic, it would have to mix its genes with those from the naturally circulating flu 'A' strain to transform so that it becomes easily transmissible from human to human, said Linda Canas, chief of the institutes’ virology section.

Influenza viruses are known to transform with some frequency. This is why surveillance exists to determine which strain is best for the current vaccine, Major Eddington said.

"With the influenza virus, two different mutations called 'shift' and 'drift' exist," Major Eddington said.

He said the drift mutation process involves a small nucleic acid variation that occurs after the virus invades a cell and during replication of its nucleic acid genome. Shift mutations, however, involve larger genetic segments and can occur in naturally circulating flu 'A' strains.

"The problem (leading to potential pandemics) is someone infected with a normal circulating flu 'A' strain is (also) co-infected with avian flu," Major Eddington said.

He said, the co-mingling of virus strains creates conditions for gene sharing. This occurs after an infected cell produces gene segments from both strains and they mix together during the process called self assembly. During this process, the virus mutates into a new variation in which humans have no immunity.

"The Air Force has stepped up worldwide avian flu surveillance. That includes research sites in South America and Thailand," Ms. Canas said.

Since 1997, the Air Force has been executive agent for the laboratory-based Global Emerging Infections System.

This tri-service system relies on a network of global sentinel (early warning) sites, Ms. Canas noted. "Our surveillance data is shared with the Food & Drug Administration's Vaccine and Related Biological Products Advisory Committee," she said.

This information is compared with other surveillance information and used to develop North American flu vaccines. Typically, flu vaccines are composed of two 'A' strains and one 'B' strain. All flu vaccines and anti-flu prescription drugs, such as the FDA-approved prophylactic Tamiflu, are made overseas.

Air Force scientists know current flu vaccines offer no protection against avian flu, Ms. Canas said.

"We have very little information on the use of Tamiflu,” she said. “The only thing that it seems to help is morbidity (onset of illness). We don't know how it will affect mortality."

(Courtesy of Air Force Materiel Command News Service)



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