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H5N1 Human Transmission in Fujian Province?
December 30, 2005
On 13 December, initial laboratory tests on samples from the patient tested negative for H5N1. But further tests on 23 December – including PCR tests carried out at the Chinese Center for Disease Control in Beijing – showed positive results. The virus was also isolated from the patient.
Agricultural authorities so far have not been able to confirm the presence of the H5 virus subtype in poultry in the vicinity of the patient’s residence or place of work. Investigators have not been able to confirm any direct contact between the patient and poultry prior to the onset of illness.
This is China’s seventh laboratory-confirmed human case. Of these cases, three have been fatal (including this latest case). To date, China has reported human cases in six provinces and regions: Hunan, Anhui, Guangxi, Liaoning, Jiangxi and Fujian.
The above comments from the latest WHO report on H5N1 rause more concerns about human to human transmission. More information about the isolated virus would be useful. Currently, only one isolate from Fujian Province from 2005 is available at GenBank, but the sequence suggests closely related H5N1 isolates are present throughout eastern China, raising concerns over human transmission via various H5N1 strains.
China’s first reported human H5N1 infection was only a few months ago and already cases have been confirmed in six eastern provinces. Tracing polymorphisms of the 2005 isolate (A/Duck/Fujian/1734/05(H5N1) indicates that it shares some polymorphisms with the H5N1 isolates from Hong Kong in 1997 as well as the Hong Kong isolates from the family that visited Fujian Province in 2003. In addition several polymorphisms found in the 2004 and 2005 isolates in southeast Asia are also present in the 2005 Fujian isolate.
The HA cleavage site, RERRRKR, matches a 2003 isolate from a duck (A/duck/China/E319-2/03(H5N1)) that was being smuggled from Fujian Province to Taiwan. The same cleavage site is also found in more recent isolates from Guangdong and Hunan Province.
Other polymorphisms are found in isolates from Hubei as well as tree sparrows in Henan and isolates from Indonesia. The various combinations of polymorphisms suggest these isolates are related but distinct, significantly increasing the number of H5N1 strains that can infect humans.
Publication of the sequences of the H5N1 isolates from humans and poultry would aid in efforts to determine how rapidly H5N1 is evolving toward more efficient human to human transmission.
The failure to identify a poultry source for the most recent case is cause for increased concern.