Bird Flu Virus Has Mutated in Turkey

Brian Handwerk
for National Geographic News

January 13, 2006

Geneticists monitoring Turkey's bird flu outbreak say the virus has
mutated, but the change poses no added threat.

So far the virus has infected 18 people and killed 3 children in the country.

Samples from two Turkish flu victims show that the virus has mutated, but not in a way that would enable human-to-human transmission.

The deadly H5N1 strain of avian influenza has appeared in poultry flocks throughout Turkey.

A 12-year-old girl and her two teenage brothers were the first bird-flu fatalities confirmed outside Southeast Asia. The siblings lived in a rural area in eastern Turkey near the Iranian border.

Turkish authorities have announced aggressive plans to cull some five million birds in an attempt to curb the spread of the disease.

The World Health Organization estimates that the H5N1 virus has infected fewer than 150 people worldwide to date, killing 78.

Experts caution that a bird flu pandemic could kill millions if the virus genetically mutates into a more contagious form.

Sick Birds

Samples from two teenage flu victims in Turkey are being analyzed at the National Institute of Medical Research (NIMR) in London at the request of the World Health Organization.

Two different strains of the virus have been discovered in the teenagers. One carried a viral mutation in a protein called hemagglutinin. Influenza viruses use hemagglutinin to attach to healthy cells.

The mutation has been previously shown to enable the avian flu virus to adhere to and infect cells, including human cells, more easily.

The same mutation was observed in virus samples from victims of the 2003 Hong Kong and 2005 Vietnam bird flu outbreaks. Experts stress that the known mutation is not in itself a reason for increased concern.

"This same mutation was identified in 2003 in Hong Kong and yet did not take off in a way that led to greater transmissibility either from chicken to human or human to human," Anthony Fauci, head of the U.S. National Institute for Allergy and Infectious Diseases, told the Reuters news service.

"It is unclear whether the mutation occurred in the person or whether it occurred in the chicken," Fauci added.

Genetic tests reveal that the Turkish flu victims almost certainly acquired the virus from sick birds, rather than from other humans.

NIMR researchers also report that the viruses found in Turkish victims are likely responsive to several antiviral drugs, including Tamiflu, which may help slow the spread of any potential pandemic.

New Tool

Earlier this week researchers from the Scripps Research Institute in La Jolla, California, unveiled a new tool that might help track any outbreak of pandemic bird flu in real time.

The technology, called a glycan array, is a grid of sugars similar to those found on the outsides of human cells.

Avian and human viruses recognize and attach themselves to different sugar structures.

Scientists using the array can identify genetic mutations that help avian flu virus strains bind more easily to human cells.

Researchers examined samples of the deadly 1918 "Spanish flu" virus and other pandemic strains, looking at specific amino acid mutations that could dramatically increase the ability of an avian virus to attach to human cells.

"It would appear that two mutations could change the specificity dramatically going from avian to human," said Scripps researcher Ian Wilson.

The array could track the appearance of any such mutations. They would likely occur, as they did during influenza pandemics in 1957 and 1968, when a primarily human virus acquired a few avian virus proteins.

"This array is basically ready for use to evaluate strains as they [adapt] from birds to humans," said James Paulson, director of the Consortium for Functional Glycomics at Scripps.

"It wasn't possible before to compare many different structures in such a way to assess very rapidly when this key mutation has occurred."

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