- The twenty 2005 H5N1 sequences at Los Alamos provide
additional clues on the emergence of the latest versions of H5N1 in Vietnam.
10 of the sequences are of HA and all 10 are missing an arginine (ARG)
residue within the HA cleavage site. The motif is not new. It was present
in sequences from Yunnan, a province in China adjacent to northern Vietnam,
as well as isolates in South Korea, Japan, and other locations in China
such as Guangdong. These data indicate the 2005 versions circulating in
both northern and southern Vietnam in 2005 are recombinants.
- However, there is a 2004 isolate (A/chicken/Viet Nam/HauGiang-617/2004(H5N1)
from Hau Giang in southern Vietnam which is also missing the ARG, and it's
match to the 2005 isolates is even closer than the earlier isolates, indicating
the recombinant appeared in Vuetnam in 2004 and was associated in time
and location with an outbreak of human cases in northern and southern Vietnam
beginning in the middle of July, 2004.
- Between the middle of July and early August, there were
human cases reported in Hau Giang in the south and Ha Tay in the north.
The two cases in the north were young children and both were confirmed
to be H5N1 positive. Only one case in the south was confirmed, because
no samples were collected on the initial cases. However, the confirmed
case in Hau Giang was an older sister of a brother and cousin that died
with bird flu symptoms. This familial cluster was unusual in that the brother
and cousin developed symptoms at about the same time, while the older sister
developed symptoms after her brother died, which is the common bimodal
distribution found in virtually all familial clusters in Vietnam and Thailand.
The bimodla distribution signals human-to-human transmission.
- The sample at GenBank is from a chicken, but was collected
from an outbreak that happened at the same time as the human cases. The
10 sequences at Los Alamos indicate that this HA cleave site recombinant
spread throughout Vietnam and was present in all 10 2005 H5N1 HA sequences.
Thus, the recombinant in 2005 was present in Vietnam in the summer of 2004,
and this recombinant emerged as the dominant genotype throughout Vitnam
- It was associated with human-to-human transmission in
the summer of 2004.
- 2005 Sequences from Northern And Southern Vietnam at
- Recombinomics Commentary
- June 29, 2005
- Twenty sequences from 2005 H5N1 isolates in Vietnam have
been placed on deposit at Los Alamos National Labs (LANL). The isolates
represent the H and N gene from 11 avian isolates in northern and southern
- From the north there are HA sequences from:
- Hanoi A/Chicken/Vietnam/NCVD09/2005
- Hanoi A/Chicken/Vietnam/NCVD10/2005
- Ha Tay A/Duck/Vietnam/NCVD01/2005
- Ha Tay A/Muscovy Duck/Vietnam/NCVD02/2005
- Vinh Phuc (A/Duck/Vietnam/NCVD04/2005
- Lao Cai (AChicken/Vietnam/NCVD12/2005.
- From the south there are:
- An Giang A/Duck/Vietnam/NCVD05/2005
- An Giang A/Duck/Vietnam/NCVD06/2005
- Tien Giang A/Duck/Vietnam/NCVD07/2005
- Tien Giang A/Duck/Vietnam/NCVD08/2005.
- All ten HA sequences are missing an ARG in the HA cleavage
site indicating all are recombinants and the missing ARG does not correlate
with the different bird flu case fatality rates in the north and south,
assuming the human isolates in 2005 are similar to the corresponding avian
- Patricia A. Doyle, PhD
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