Posted on 09/13/2005 4:38:27 PM PDT by Mother Abigail
Avian Influenza (H5N1) Viruses Isolated from Humans in Asia in 2004 Exhibit Increased Virulence in Mammals
The spread of highly pathogenic avian influenza H5N1 viruses across Asia in 2003 and 2004 devastated domestic poultry populations and resulted in the largest and most lethal H5N1 virus outbreak in humans to date.
To better understand the potential of H5N1 viruses isolated during this epizootic event to cause disease in mammals, we used the mouse and ferret models to evaluate the relative virulence of selected 2003 and 2004 H5N1 viruses representing multiple genetic and geographical groups and compared them to earlier H5N1 strains isolated from humans.
Four of five human isolates tested were highly lethal for both mice and ferrets and exhibited a substantially greater level of virulence in ferrets than other H5N1 viruses isolated from humans since 1997.
One human isolate and all four avian isolates tested were found to be of low virulence in either animal. The highly virulent viruses replicated to high titers in the mouse and ferret respiratory tracts and spread to multiple organs, including the brain.
Rapid disease progression and high lethality rates in ferrets distinguished the highly virulent 2004 H5N1 viruses from the 1997 H5N1 viruses. A pair of viruses isolated from the same patient differed by eight amino acids, including a Lys/Glu disparity at 627 of PB2, previously identified as an H5N1 virulence factor in mice.
The virus possessing Glu at 627 of PB2 exhibited only a modest decrease in virulence in mice and was highly virulent in ferrets, indicating that for this virus pair, the K627E PB2 difference did not have a prevailing effect on virulence in mice or ferrets. Our results demonstrate the general equivalence of mouse and ferret models for assessment of the virulence of 2003 and 2004 H5N1 viruses.
However, the apparent enhancement of virulence of these viruses in humans in 2004 was better reflected in the ferret.
Wild waterfowl are the natural reservoir of all influenza A viruses, and these viruses are usually nonpathogenic in these birds. However, since late 2002, H5N1 outbreaks in Asia have resulted in mortality among waterfowl in recreational parks, domestic flocks, and wild migratory birds.
The evolutionary stasis between influenza virus and its natural host may have been disrupted, prompting us to ask whether waterfowl are resistant to H5N1 influenza virus disease and whether they can still act as a reservoir for these viruses.
To better understand the biology of H5N1 viruses in ducks and attempt to answer this question, we inoculated juvenile mallards with 23 different H5N1 influenza viruses isolated in Asia between 2003 and 2004. All virus isolates replicated efficiently in inoculated ducks, and 22 were transmitted to susceptible contacts.
Viruses replicated to higher levels in the trachea than in the cloaca of both inoculated and contact birds, suggesting that the digestive tract is not the main site of H5N1 influenza virus replication in ducks and that the fecal-oral route may no longer be the main transmission path.
The virus isolates' pathogenicities varied from completely nonpathogenic to highly lethal and were positively correlated with tracheal virus titers. Nevertheless, the eight virus isolates that were nonpathogenic in ducks replicated and transmitted efficiently to naïve contacts, suggesting that highly pathogenic H5N1 viruses causing minimal signs of disease in ducks can propagate silently and efficiently among domestic and wild ducks in Asia and that they represent a serious threat to human and veterinary public health.
FYI
Thank you for the ping. I look for sustained h2h H5N1 this fall or winter.
JA!!! Where you been....glad you're back!!!
got time for the ping list or is this an in and out????
Welcome back!
Any news on a vaccine?
Done..
bitt, you probably have the most current ping list. Would you please use it?
I'll be around for a couple of hours this evening.
I've read various things that several far east countries SAY they have an H5N1 vaccine, but NOTHING that has been in a peer-reviewed journal or with double-blind studies, or anything that I actually believe.
I don't believe there is any vaccine.
Great to see you back!
Thanks!
I would appreciate being on you ping list, too. I am in the final semester before RN school. Microbiology and A&P II keep me from my FReeping some times, but it would be nice to get notified on this topic. Thanks!
While you're updating your ping list, could you include me, too?
I don't have a health background.
Agriculture is my emphasis.
Done
Alaskan Ducks Tested for Bird Flu
Stefan Lovgren
for National Geographic News
September 13, 2005
......
Migrating birds may have caused the outbreak of avian flu that killed thousands of domestic fowl in Siberia this summer. Scientists have also found birds on Lake Qinghai in China, where many birds come to migrate, to be infected with the strain.
Fearing that the virus may be spreading from Asia to other parts of the world, bird experts in Alaska have in recent weeks been testing migratory birds there for avian influenza.
If avian flu is introduced to North America by migrating birds, "Alaska is the most likely state where it would first arrive, because that's where the … flyways intersect," said Hon Ip, director of the U.S. Geological Survey's (USGS) virology lab in Madison, Wisconsin. His lab is handling some of the tests.
Hon Ip? I wonder if he's related to the ebola doctor, Benjamin Ip?
I'm gonna quit wishing for things to not happen....I'm three for three.
NIAID Initiates Trial of Experimental Avian Flu Vaccine
Test of avian flu vaccine succeeds
Fauci said that though the vaccine that has undergone preliminary tests - including some in Maryland - could be used on an emergency basis if a pandemic developed, it would be several months before that vaccine is tested further and, if licensed, offered to the public.
IIRC, phase two studies are being started.
Thanks for that information. I read in your link that the vaccine is made from virus isolated from one of the Vietnam cases. That virus is not efficient in human-to-human transmission. The vaccine we will need will be the one that will protect us from a further mutated virus, one that is capable of sustained human-to-human transmission. Such a virus will probably be a combination of H5N1 with another influenza virus in a mammal, perhaps a pig, that contracts them both at the same time.
To my knowledge, there is no way to make a vaccine for a virus that has not evolved yet. I could be wrong.
Actually, H5N1 has been around since 1997, when it killed 6 out of 18 humans it infected in Hong Kong, and I've been more or less watching it since.
Over a million birds were killed in an attempt to destroy this virus, and it came back.
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