A previously unknown and dangerous strain of H5N1 bird flu has
emerged from southern China and has spread from birds to people in
Southeast Asia, marking a 3rd wave of avian flu and rekindling fears
of a global pandemic. Although the H5N1 avian influenza mostly
affects birds and infects people only sporadically, the new strain
[correctly described as a sub-lineage of H5N1 avian influenza virus -
Mod.CP] will once again raise fears that it may mutate or combine
with a human virus to form a mutant or hybrid capable of passing from
person to person, triggering a pandemic where millions of lives may be lost.
"The implications of this study are that current control measures, as
generally practised to control avian influenza, are ineffective,"
said Prof Yi Guan of the University of Hong Kong, leader of a large
team that describes the virus today in the Proceedings of the
National Academy of Sciences. Prof Guan, director of the State Key
Laboratory of Emerging Infectious Diseases, who collaborated with
Prof Robert Webster of St Jude's Children's Research Hospital in
Memphis, a leading centre in the West, concludes that "the pandemic
threat persists."
"We have no information to suggest that this is more highly
pathogenic or that this virus is a more likely candidate for a
pandemic virus than any other H5N1 or other subtype virus," he told
The Daily Telegraph. However, the team points out that a highly
pathogenic H5N1 influenza virus in Eurasian and African poultry
populations is considered the most likely candidate for a new
pandemic influenza and the rise of avian-to-human interspecies
transmission seen in the last 12 months "seems to favour such a hypothesis."
For today's study, the team searched for different viral strains by
monitoring the H5N1 avian influenza virus in market chickens, ducks,
and geese. The researchers found that a strain emerged last year and
became the dominant strain in southern China by early this year,
displacing previous ones. The strain appeared to avoid China's
compulsory chicken vaccination programme, and may even be aided by
the vaccine, which may be ineffective against the new strain.
The new strain was also responsible for recent human H5N1 infections
in China, which have occurred in rural and urban areas, some of which
could not be linked to nearby outbreaks in farms or local markets.
The researchers warn that such urban human infections could lead to a
serious outbreak, challenging current pandemic preparedness plans.
These new viruses have already transmitted to Hong Kong, Laos,
Malaysia and Thailand, resulting in a new transmission and outbreak
wave in Southeast Asia, say the team. "The predominance of this virus
over a large geographical region within a short period directly
challenges current disease control measures," the team concludes.
This strain may have begun the 3rd wave of transmission of H5N1 avian
flu that could spread throughout Eurasia. Without more and broader
flu surveillance in both poultry and humans, say the researchers,
identifying an outbreak of human H5N1 influenza will be difficult.
telegraph.co.uk |
