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Suspect H5N1 Clusters In Mekong Delta Vietnam
December 30, 2006
A 36-year-old woman and her three children aged three to 13 were admitted to Nam Can Hospital in Ca Mau province this past week with fevers, coughing, decreased white blood cells and damaged lungs, said Ho Van Van, a doctor at the hospital.
The family had four chickens and five ducks, and ate one of the chickens, which had fallen sick and died, on Dec. 23, he said.
Nguyen Huu Minh, deputy head of the animal health department of Soc Trang reported two people in My Tu district had difficulty breathing after eating chicken.
The above comments described two clusters of suspect H5N1 cases in the Mekong Delta. The cluster in Ca Mau is a familial cluster. These cases in Vietnam, coupled with the outbreaks in South Korea, are similar to reported outbreaks of H5N1 in December, 2003. Vietnam was the first country to report patients with bird flu symptoms, and South Vietnam was the first country to report an H5N1 outbreak.
Although the two outbreaks in December, 2003 were close in time, genetically the H5N1 was readily distinguishable. The isolates from Vietnam were Clade 1 (see phylogenetic tree of vaccine targets), while Korea was Clade 2. Included in the differences were two amantadine resistance changes in the M2 of the Clade 1 isolates. Clade 1 isolates were subsequently found in neighboring countries (Thailand, Laos, and Cambodia). In 2003/2004 Clade 2 isolates were reported in Japan, multiple provinces in China, and Indonesia. More recently, the Fujian strain (Clade 2 sub-clade 3) migrated into the region and has been detected in Vietnam, Thailand, Laos, and Malaysia. It is also widespread in China and found in all reported human cases in China in 2005/2006.
H5N1 subsequently spread outside of the region after the Qinghai strain (Clade 2 sub-clade 2) was detected at Qinghai Lake in May, 2005. It was carried by long range migratory birds to countries to the west of China, including Europe, the Middle East, and Africa. Those birds are now migrating south, and the recent outbreaks of H5N1 in South Korea have been the Qinghai strain, which has genetic similarities with the 2003 isolates from South Korea / Japan.
Thus, the role of migratory birds in the spread of H5N1 is not a new development, and the increased reports of H5N1 in poultry in Korea, and suspect patients in Vietnam. as well as human and bird cases in Egypt, is not a coincidence.