New study tracks spread of H5N1 variant in Egypt recently identified as major epicenter for virus

Published on February 10, 2014 at 1:08 AM · No Comments

Since its first identification in Asia, highly pathogenic avian influenza-H5N1-has caused significant alarm in the scientific community. While the virus' primary target is birds-tens of millions have already died from it-it is capable of infecting mammals, including humans, causing serious illness and a frightening rate of mortality.

In a new study, Matthew Scotch, a researcher at Arizona State University's Biodesign Institute, tracks the spread of an H5N1 variant in Egypt-a country recently identified as a major epicenter for the virus. In results recently appearing in the journal BMC Genomics, Scotch tracks the spread of H5N1 cases using a technique known as phylogeography.

The authors hope that studies of this kind will significantly enhance efforts by public health officials to identify viral outbreaks, limit their spread, coordinate vaccination efforts, reduce mortality and better inform the public of risks.

"Egypt represents an epicenter for H5N1 and there are new variants that have emerged since it was first discovered there in 2006, "Scotch says. "We used phylogeography and influenza genome sequences to model diffusion and evolution of the virus."

Phylogeography was born out of the fields of biogeography and phylogenetics or molecular evolution. By combining viral sequence data and geographical information over time, as well as evaluating features associated with viral carriers, researchers can better understand how viruses spread across a landscape through animal and human populations.

Phylogeography has already been established as a powerful technique for investigating viral dispersal for human diseases, including dengue fever, rabies, influenza and HIV. Recent application of phylogeographic methods to the study of avian influenza promises to significantly improve fine-grained mapping of viral origin and spread.

Avian flu H5N1 is a form of influenza A-an RNA virus- first identified in Hong Kong in 1997. The initial cases of H5N1 were apparently not transmitted efficiently among birds. In 2002 however, new isolates of H5N1 appeared, causing acute disease in ducks, resulting in neurological dysfunction and death.

Infected birds transmit H5N1 to one another through nasal secretions, saliva, feces and blood. Other animals, including humans, may become infected with the virus through direct contact with avian bodily fluids or through contaminated surfaces.

Human cases of H5N1 often result from contact with infected poultry, particularly in live bird markets and farms, which are believed to be major reservoirs for the virus. Avian H5N1 however, is also carried by migratory species of birds, which further spread H5N1 to other parts of the world.

In 2004, researchers discovered that H5N1 is a more potent pathogen than originally assumed, attacking waterfowl, chickens, crows, pigeons and ducks, as well as mammals, yielding a high mortality rate. Avian flu is now considered a significant global health threat, with the very real prospect of an international pandemic, causing widespread fatality.

Indeed, the mortality rate in humans contracting H5N1 has been estimated to be around 60 percent, making it more lethal for infected individuals than Spanish influenza-a genetically similar strain that killed 50-100 million people worldwide during the pandemic of 1918.

Currently, H5N1 is not highly transmissible to humans from birds and has a very low rate of human-to-human transmission, (though around a half dozen cases have been reported). Should a small number of mutations render H5N1 more easily transmissible among humans, the conditions for a deadly pandemic will have been met.

In addition to mutations, mixed forms of influenza virus-known as reassortant strains-can occur when a single individual is infected with two versions of a given virus and they exchange genes. An H5N1 reassortant could render avian influenza readily transmissible between human hosts.

In the new study, a particular variant of H5N1, labeled, was observed in Egypt. There, avian flu has already killed thousands of birds and caused 173 human cases, of which 63 have been fatal as of December 10th, 2013, according to the World Health Organization. These are the highest case numbers for H5N1 outside of Asia. As in the case of Asian H5N1, experts associate most human infections in Egypt with exposure to diseased poultry, particularly at live bird markets.

In their attempts to identify the origin and spread of the virus in Egypt, researchers made use of a new software platform created by Professor Scotch. Known as ZooPhy, the program enables the phylogeographic analysis of H5N1 spread. (Maps of viral spread made with ZooPhy may be seen in the accompanying video below.)

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