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Avian influenza, H5N1/97- like viruses - China

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From ProMED-mail

Date 00:42 Jun 23

Subject PRO/AH/EDR> Avian influenza, H5N1/97-like viruses - China (Hong

Kong)

 

AVIAN INFLUENZA, H5N1/97-LIKE VIRUSES - CHINA (HONG KONG)

*****************************************************

Tue 18 Jun 2002

ProMED-mail <promed

Source: Reuters Health eLine, Tue 18 Jun 2002 [edited]

<http://www.reutershealth.com/frame2/eline.html>

 

 

Research Provides Clues to 1997 'Bird Flu' Outbreak

------------------

NEW YORK: Recent outbreaks of [avian influenza] " bird flu " in Hong Kong did

not spread to people as [the outbreak] in 1997 did, but studying these

outbreaks help scientists understand how viruses jump from birds to humans.

 

During the 1997 outbreak, 6 people died after being infected with a strain

of influenza virus that previously had infected only birds. To control the

spread of the virus, more than 1.5 million chickens and other poultry were

slaughtered in the Hong Kong area. Since the 1997 outbreak, Hong Kong has

taken several steps to reduce the risk of another outbreak. Geese and ducks

are now slaughtered at a central facility to keep viruses from spreading to

chicken and other poultry. The 1997 virus is thought to have originated in

geese and other birds that live in water and to have crossed over to

land-living birds.

 

Although the virus that caused the 1997 outbreak has not reappeared in the

region, several viruses believed to be precursors of the species-jumping

virus have been detected, according to a report in the June 25th issue of

the Proceedings of the National Academy of Sciences [ref: Proceedings of

the National Academy of Sciences 2002;99:8950-8955; online 19 Jun 2002

<http://www.pnas.org/cgi/content/abstract/132268999v1>]. In fact, between

Feb and May 2001, several of these viruses moved from geese and ducks to

chicken and other land poultry, leading to an outbreak of disease in Hong

Kong markets.

 

The viruses found in 2001 " were not the same as those found causing disease

in man in 1997, " according to J.S.M. Peiris, one of the researchers

involved in the study. The 1997 virus was unique in that it was an avian,

or bird, virus that directly infected and caused serious illness in people,

Peiris said. Even though there were no documented cases of human infection

with the bird viruses detected recently, Peiris and colleagues found signs

that the viruses had changed in certain ways to make it possible to move

from geese and ducks to chicken and other poultry. These changes could have

also occurred in the early development of the 1997 virus, according to the

researchers. The 2001 viruses were able to infect mice and spread to the

brain, which [avian influenza] viruses normally are not capable of

doing. These unusual qualities of the virus do not prove that they could

infect humans, but they do raise concerns, the authors report.

 

Unlike in 1997, in 2001, and during a more recent case in 2002,

surveillance of poultry markets provided an early warning, so the outbreak

was kept under control. But the researchers note, " Measures in Hong Kong

are not likely to reduce the possibility of such a virus arising in the

wider region of East Asia including southern China that has been recognized

as an influenza epicenter. "

 

[byline: Merritt McKinney]

 

--

ProMED-mail

<promed

 

[The PNAS paper referred to above is entitled: " Emergence of multiple

genotypes of H5N1 avian influenza viruses in Hong Kong SAR, " and is

authored by Y. Guan , J. S. M. Peiris , A. S. Lipatov, T. M. Ellis, K. C.

Dyrting, S. Krauss, L. J. Zhang, R. G. Webster, and K. F. Shortridge. The

abstract of the paper states that: Although A/Hong Kong/156/97

(H5N1/97)-like viruses associated with the " bird flu " incident in Hong Kong

SAR have not been detected since the slaughter of poultry in 1997, its

putative precursors continue to persist in the region. One of these,

Goose/Guangdong/1/96 (H5N1 Gs/Gd)-like viruses, reassorted with other avian

viruses to generate multiple genotypes of H5N1 viruses that crossed to

chickens and other terrestrial poultry from its reservoir in geese. Whereas

none of these recent reassortants had acquired the gene constellation of

H5N1/97, these events provide insight into how such a virus may have been

generated. The recent H5N1 reassortants readily infect and kill chicken and

quail after experimental infection, and some were associated with

significant mortality of chickens within the poultry retail markets in Hong

Kong. Some genotypes are lethal for mice after intra-nasal inoculation and

spread to the brain. On this occasion, the early detection of H5N1 viruses

in the retail, live poultry markets led to preemptive intervention before

the occurrence of human disease, but these newly emerging, highly

pathogenic H5N1 viruses provide cause for pandemic concern.

 

This study confirms the inference that H5N1-type influenza viruses with

novel combinations of other genes are being continuously generated by

reassortment from the pool of influenza viruses present in wild and

domesticated birds in the South China area and that the poultry markets of

the Hong Kong SAR provide a convenient focus for surveillance of new

strains of H5N1 (and other antigenic types) with potential for spread in

non-avian hosts. - Mod.CP]

 

[see also:

Avian influenza, transmission to humans: genetics 20020106.3179 2001

Avian influenza - China (Hong Kong) (02) 20020206.3492

Avian influenza - China (Hong Kong) (11) 20020530.4362

2001

----

Avian influenza, H5N1 - China (Hong Kong) (02) 20010517.0962

Avian influenza, H5N1 - China (Hong Kong) (06) 20010528.1038

Avian influenza - China (Hong Kong) 20010420.0778

Avian influenza - China (Hong Kong) (02) 20010710.1332]

....................cp/mpp

 

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