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Human H5N1 Bird Flu Infections in China in 2004 and 2005
July 15, 2005
First sampled in Qinghai, this is the most powerful strain found so far. This can be transmitted from poultry to human and from human to human. However, this strain of virus is unable to transmit from human to poultry. The diagnosis of this virus is extremely complicated. Incubation period is short and causes of deaths are mainly mis-diagnosis.
The above is the translation of the description of the H5N1 strain causing fatalities in Qinghai. A brief summary of the translations follows. The original story has more detail.
The report describes 10 strains of H5N1 isolated in China in 2004 and 2005. These represent 9 variants of H5N1 and they are placed into three categories. One is only known to infect birds, one that can also infect humans (R series), and one group that is still being characterized (X series).
17B was isolated in Hunan in July, 2004. It is carried asymptomatically in domestic birds. In November, 2004 another isolate 19A was isolated the Shantou. This isolate is probably similar to the 2005 Shantou isolates described in the Nature paper. A third isolate 19A is resistant to the vaccine. These three isolates do not infect humans.
R12 is a strain initially isolated in Xinjiang in 2004. It is like some of the isolates in northern Vietnam and only produces mild disease in humans. The virus was subsequently found in Guangdong and Zhanjiang. The 2005 variant of the virus is RW4.
The virus that causes lethal infections in humans is RK7. It produces complex symptoms and has a short incubation period. It is frequently fatal.
Three other isolates have not been characterized. X1 is a 2004 human isolate. X2 is from Qinghai. X3 is from Qinghai, Hunan, and Ningxia. These uncharacterized H5N1 may be found in association with other H5N1's.
The above descriptions would indicate that there are unreported human H5N1 infections in China, but few produce lethal infections other than the Qinghai isolates. The Qinghai isolates are of concern. The boxun reports describe two clusters suggesting the virus can be transmitted and is lethal. These latest reports do not give numbers infected or dead, they just describe a cluster of two and a cluster of four. Symptoms are both gastrointestinal and respiratory and all six patients die.
The reports have not been verified, but boxun reports on the birds at Qinghai Lake have now been confirmed with reports by WHO and Hong Kong. There have been no reported human cases in China, but the 2005 isolates in southeastern China have not been reported, but sequences have now been published, strongly suggesting that the infections have not been reported.
The widespread infections by H5N1 in China are supported by the boxun report, except the report describes mild human cases in 2004 and 2005 as well as fatal cases in Qinghai in 2005. The detection of multiple strains in individuals is cause for concern regarding more recombination as well as the catastrophic spread of lethal human H5N1 by migratory birds.