North Korea has Asia's first outbreak of H7 avian flu

April 5, 2005 (CIDRAP News) – The strain of avian influenza responsible for the deaths of 219,000 poultry in North Korea is not the same as the lethal H5N1 strain many experts fear could cause a worldwide pandemic.

Tests conducted by the United Nations Food and Agriculture Organization (FAO) have confirmed that the virus in North Korea is an H7 strain, although further subtyping has not been completed, according to an Associated Press (AP) story today.

An FAO official said the discovery marks the first time an H7 outbreak has been identified in Asia, where H5N1 has caused poultry outbreaks in nine Asian countries and 50 human deaths in 3 countries since 2003.

The FAO's Hans Wagner traveled to North Korea when news of the outbreak surfaced in late March. "We have a new situation because H7 has so far not occurred in Asia," Wagner told Reuters television in Beijing today, following his trip.

"We want to know: How did it come to such a large farm with relatively good biosecuirty measures?" the AP quoted Wagner as saying. Three factory-style farms within 3 miles of Pyongyang, the North Korean capital, have been affected, news services said.

Wagner described North Korean officials as "very cooperative" and said they had approved testing of bird samples by labs in China, Britain, and Australia, according to the AP.

News of the outbreak has generated concern about its possible effects on North Korea's poultry industry. The impoverished, secretive Communist state was thought to have about 25.5 million poultry in 2004, following a massive push to re-establish a local food supply. North Korea has seen widespread famine as a result of many factors, including natural disasters and bad harvests in the mid-1990s. The country has depended on foreign aid to feed its people.

By North Korea's official reckoning, famine has killed 200,000 people; international estimates range from 1.5 million to 3 million deaths, according to a 2000 estimate by the nonprofit group Medecins Sans Frontieres (MSF).

No human illness cases have been reported in connection with the North Korean outbreak, but H7 viruses have been known to spread from poultry to people before. A recent World Health Organization (WHO) report lists 93 human cases, including one death, as the result of H7 infections. All but four of these were linked with a major avian flu outbreak in the Netherlands in 2003.

Although H7 viruses have made people ill, the cases have not been as severe as those in the current H5N1 outbreak in Southeast Asia. In most cases the symptoms, if any, were limited to conjunctivitis, according to the WHO. However, in the Dutch outbreak in 2003, a 57-year-old veterinarian died.

Follow-up research on the Dutch outbreak suggested there were high rates of transmission of the virus from chickens to people and secondary transmission from person to person. At least 50% of people exposed to infected poultry in the outbreak were later found to have H7 antibodies, according to a 2004 report by the Dutch National Institute for Public Health and the Environment (RIVM).

Further, 59% of people who hadn't had contact with infected poultry but had household contact with an infected poultry worker had H7 antibodies, according to the RIVM. In all, researchers estimated that 1,000 to 2,000 people were infected with H7N7 in that outbreak, far more than the 89 cases officially reported.

"This suggests that the population at risk for avian influenza was not limited to those with direct contact to infected poultry, and that person-to-person transmission may have occurred on a large scale," the researchers concluded.

Four H7 subtypes—H7N1, H7N4, H7N3, and H7N7—have been identified in highly pathogenic avian influenza poultry outbreaks, according to the WHO. It's not yet clear which H7 subtype has sickened birds in North Korea. Further subtyping of the virus is pending, news services reported today.

See also:

WHO report "Avian Influenza: Assessing the Pandemic Threat"
http://whqlibdoc.who.int/hq/2005/WHO_CDS_2005.29.pdf

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