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Bird flu research points to urban fringes

FORUM Staff

Bird flu remains a persistent threat that has killed hundreds of people and millions of poultry throughout the Indo Asia Pacific since a series of deadly outbreaks began in 2003.

A new study led by researchers at the Honolulu-based East-West Center now confirms that transition zones between rural and urban areas act as hot spots for outbreaks of this highly infectious disease.

East-West Center researchers working in Vietnam found that these zones on the outskirts of cities often feature densely populated neighborhoods existing alongside high densities of domesticated chickens, ducks and geese. This creates ideal conditions for the transmission of H5N1, the deadly strain of bird flu, noted the study, which was funded by the U.S. National Science Foundation. Researchers Sumeet Saksena and Jefferson Fox published the study in September 2015 in the open-access journal PLOS ONE. They focused on bird flu outbreaks in Vietnam between 2003 and 2005 that led to 45 million bird deaths and 106 confirmed human cases with 52 deaths, according to the study.

Their research concluded that these outbreaks emerged due to converging environmental and social risk factors brought on by development in these rural-urban transition zones, which the researchers call peri-urban zones.

“Emergence risk should be highest in the most rapidly transforming urban areas — peri-urban zones where mixes of urban-rural, modern-traditional land uses and poultry husbandry coincide most intensely,” the researchers wrote.

Bird flu remains a threat in the Indo Asia Pacific. Since 2003, the virus has killed 449 humans in 14 countries, according to World Health Organization data as of October 2015. That includes 167 people in Indonesia, 64 in Vietnam, 37 in Cambodia, 31 in China, 17 in Thailand, two in Laos and one in Bangladesh.

The researchers said their study implies a need for authorities to go beyond isolating flocks of poultry birds in individual facilities to the so-called landscape level when attempting to contain outbreaks of bird flu. The researchers said that planners need to develop these broader bio-security measures using geographic tracking of risk factors along with pathogen surveillance programs.

Researchers said the study has the potential to inform the design of future research on other emerging infectious diseases in Vietnam and elsewhere.

“We speculate that in Southeast Asia, Japanese encephalitis, the transmission of which is associated with rice cultivation and flood irrigation, may also show a strong association with peri-urbanization,” they wrote. “In some areas of Asia these ecological conditions occur near, or occasionally within, urban centers.”

“Likewise, Hantaan virus, the cause of Korean hemorrhagic fever, is associated with the field mouse Apodemus agrarius and rice harvesting in fields where the rodents are present. Our work has demonstrated that the percentage of land under rice in peri-urban areas and rural areas is similar.”

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