HONG KONG, April 26
(Xinhua) -- Chinese scientists have made
a breakthrough in understanding the
human infections with avian influenza
A
H7N9 virus by finding out
that poultry wet market might be
the source of the deadly virus,
according to a research published
online on Thursday by the leading
international medical journal The
Lancet.
The research was
conducted by a collaborative research
team from The University of Hong
Kong and Zhejiang University. They
analyze four infected patients in
southeast China's Zhejiang Province,
and discover for the first time
that the patient's virus is
genetically very closely related (>/=99.4%)
to the chicken virus isolated from
the epidemiologically linked poultry
market.
The Lancet publishes
the research entitled "Human infections
with the emerging avian influenza A
H7N9 virus from wet market poultry:
clinical analysis and characterization of
viral genome" in a timely manner,
according to a statement from The
University of Hong Kong.
The
research analyses four epidemiologically
unlinked Zhejiang patients suffering from
severe acute community acquired pneumonia
not responding to typical and atypical
antimicrobial coverage who are found
to have the H7N9 virus.
The
team shows for the first time
that the patient's virus is
genetically very closely related (>/=99.4%)
to the chicken virus isolated from
the epidemiologically linked poultry market.
Indeed about 20% of the chickens in
the epidemiologically linked markets were
infected with this virus. The
researchers thereby believe that poultry
wet market might be the source
of virus of avian influenza A H7N9
human infection.
Moreover, the
team conducts a characterization of
viral genome. They find that the
patient virus has a PB2 Asp701Asn mutation
which is important for adaptation to
mammalian host. There are also
important mutations on the haemagglutinin,
a virus surface protein, facilitating
the virus attaching to mammalian host
cell. These include the HA Gly186Val
and Gln226Leu.
But no person-to-person
transmission was found in 303 household
or workplace contacts and 82 health-care
workers with unprotected exposure to
the four patients, according to the
research.
Among these four
patients, two of them died with
respiratory failure, multiorgan dysfunction
and markedly elevated serum cytokines
and chemokines when compared with the
survivors. Research found fatal but
not the mild cases exhibit aberrant
proinflammatory response of "cytokine
storms," which resembles that observed
in H5N1 or SARS patients. Another
important finding is that virus
testing appeared to be more sensitive
with lower respiratory tract specimens
such as sputum than throat
swabs.
All in all, further
studies on the virus evolution and
disease pathogenesis will be performed
to improve disease management and
epidemic control, said the
statement.
The research team is
led by Professor Li Lanjuan of
Zhejiang University and Professor Yuen
Kwok-yung, the Co-director of the
State Key Laboratory of Emerging
Infectious Diseases, Department of
Microbiology of The University of Hong
Kong Li Ka Shing Faculty of
Medicine.
The deadly H7N9 virus
has caused a total of 108 human
infections on the Chinese mainland,
including 23 cases that have ended in
death, the National Health and Family
Planning Commission said on
Wednesday.
Latest
development of H7N9 in
China[Special]