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Reuters story:
Bird flu causes fatal immune storm - study
Fri Nov 11, 2005 5:46 AM GMT

By Maggie Fox, Health and Science Correspondent

WASHINGTON (Reuters) - Scientists in Hong Kong say they may have helped
explain why the H5N1 bird flu virus kills so many healthy young adults -- it
apparently causes a "storm" of immune system chemicals that overwhelms the
patient.

The H5N1 virus caused proteins known as cytokines to rush to infected lung
tissue -- evidence of a so-called cytokine storm, an immune system
overreaction that can be fatal.

The study, published in the online medical journal Respiratory Research,
might suggest that if H5N1 does cause a pandemic, it could
disproportionately affect the young and healthy as compared with seasonal
flu, which kills many elderly people but few young adults.

It also raises questions about how effective drugs will be in controlling
such a pandemic, experts said.

"We have to see if it is true and if we can do anything about it," cautioned
Dr. Anthony Fauci, head of the U.S. National Institute of Allergy and
Infectious Diseases, who was not involved in the research.

But if the experiment does accurately show what happens in people, it may
mean patients with H5N1 infections will need drugs that depress the immune
response in addition to antivirals, Fauci said.

The H5N1 flu has swept through flocks of poultry but has so far infected
only 124 people in four countries and killed 64 since it re-emerged in 2003.

It does not easily infect people, but when it does, it kills about half of
them.

"The reasons for this unusual severity of human disease have remained
unclear," Michael Chan and Malik Peiris of the University of Hong Kong and
colleagues wrote in their report.

They took samples of H5N1 from a patient who died of the infection in a 1997
outbreak, from two patients infected in Vietnam in 2004, and a sample of a
Hong Kong patient with ordinary H1N1 seasonal flu.

They used the virus to infect lung tissue samples taken from other, non-flu
patients.

CHEMICAL STORM

The H5N1 viruses brought in a storm of cytokines -- the immune system's
inflammatory chemicals -- including IP-10, interferon beta, RANTES and
interleukin-6. The H1N1 virus caused a much smaller effect.

And the later, Vietnamese strains caused a bigger cascade than the 1997 H5N1
strain.

This could be because of continued mutations, the researchers said. "The
H5N1 viruses have continued to reassort, acquiring different internal genes
from other influenza viruses of avian origin," the researchers wrote.

The study, published on the Internet at http://respiratory-research.com/,
may explain the severe respiratory distress suffered by H5N1 patients, who
often say they struggle to breathe.

Michael Osterholm, an infectious disease expert at the University of
Minnesota who has been advising the U.S. government on the risks of a flu
pandemic, said the study supports predictions that any possible H5N1
pandemic would be especially severe.

It means being young and healthy could actually work against people who
become infected.

"Anyone could experience this very severe, life-threatening illness,"
Osterholm said in a telephone interview.

"This is looking more and more like an H1N1 1918."

The worst recorded influenza epidemic was in 1918, when an H1N1 strain swept
the globe in a few months, killing anywhere between 20 million and 100
million people, depending on the estimate. In comparison, a pandemic in 1957
killed 2 million and one caused by an H3N2 virus in 1968 killed 1 million.

"In 1918, even among the very young and the very old, there was a ten-fold
increase in deaths," Osterholm said. "There was a 1,000-fold increase in
young adults."

Fauci said researchers are now testing various drugs that may affect the
immune system to see if they would help patients better survive H5N1.

C Reuters 2005.

http://today.reuters.co.uk/news/NewsArticle.aspx?type=scienceNews&storyID=20
05-11-11T054552Z_01_FLE100082_RTRIDST_0_SCIENCE-BIRDFLU-STORM-DC.XML