DONALD G. McNEIL Jr.
Published: January 8, 2009
Excerpts:
Exactly how the Tamiflu-resistant strain emerged is a mystery, several experts said.
Resistance appeared several years ago in Japan, which uses more Tamiflu than any other country, and experts feared it would spread.
But the Japanese strains were found only in patients already treated with Tamiflu, and they were “weak” — that is, they did not transmit to other people.
“This looks like a spontaneous development of resistance in the most unlikely places — possibly in Norway, which doesn’t use antivirals at all,” Dr. Monto said.
Dr. Henry L. Niman, a biochemist in Pittsburgh who runs recombinomics.com, a Web site that tracks the genetics of flu cases worldwide, has been warning for months that Tamiflu resistance in H1N1 was spreading.
Dr. Niman argues that it started in China, where Tamiflu use is rare, was seen last year in Norway, France and Russia, then moved to South Africa (where winter is June to September), and back to the Northern Hemisphere in November.
The mutation conferring resistance to Tamiflu, known in the shorthand of genetics as H274Y on the N gene, was actually, Dr. Niman said, “just a passenger, totally unrelated to Tamiflu usage, but hitchhiking on another change.”
The other mutation, he said, known as A193T on the H gene, made the virus better at infecting people.
Furthermore, Dr. Niman blamed mismatched flu vaccines for helping the A193T mutation spread. Flu vaccines typically protect against three flu strains, but none have contained protections against the A193T mutation.
Dr. Joseph S. Bresee, chief of flu prevention at the disease control agency, said he thought Dr. Niman was “probably right” about the resistance having innocently piggy-backed on a mutation on the H gene — which creates the spike on the outside of the virus that lets it break into human cells. But Dr. Bresee said he doubted that last year’s flu vaccine was to blame, since the H1 strain in it protected “not perfectly, but relatively well” against H1N1 infection.
Dr. Niman said he was worried about two aspects of the new resistance to Tamiflu. Preliminary data out of Norway, he said, suggested that the new strain was more likely to cause pneumonia.
The flu typically kills about 36,000 Americans a year, the C.D.C. estimates, most of them the elderly or the very young, or people with problems like asthma or heart disease; pneumonia is usually the fatal complication.
And while seasonal flu is relatively mild, the Tamiflu resistance could transfer onto the H5N1 bird flu circulating in Asia and Egypt, which has killed millions of birds and about 250 people since 2003. Although H5N1 has not turned into a strain, as many experts recently feared it would, it still could — and Tamiflu resistance in that case would be a disaster.
http://www.nytimes.com/2009/01/09/health/09flu.htmlAvian Flu Becoming More Resistant To Antiviral Drugs, Says University Of Colorado Study
08 Jan 2009
Excerpts:
While H5N1 is not highly communicable to humans from birds or between humans, experts are concerned future evolution of this subtype or other subtypes, or genetic re-assortment between subtypes, could make an avian influenza strain more contagious with the potential to cause a pandemic.
http://www.medicalnewstoday.com/articles/134781.php
Excess use makes bird flu drug futile
8 Jan 2009
Excerpts:
But in the larger dynamic, perhaps it serves as a cautionary tale," said Daniel Janies, study co-author and an associate professor of biomedical informatics at Ohio State University.
Seasonal Influenza in Asia had developed resistance against the antiviral drug adamantane and this was discovered in 2002 but by 2006 the drug was declared worthless as a treatment for the flu because more than 90% of the strains had developed a resistance to the drugs.
http://timesofindia.indiatimes.com/Health__Science/Excess_use_makes_bird_flu_drug_futile/articleshow/3952398.cms
Excessive Use Of Antiviral Drugs Could Aid Deadly Flu According To Study
08 Jan 2009
Excerpts:
The study also showed that the mutation-mediated cases of drug resistance didn't start in just one strain of avian flu. One resistant strain originated in China and spread through Southeast Asia, while another strain that was originally susceptible to adamantanes spread to Indonesia and then independently developed resistance in that country.
-snip-
http://www.medicalnewstoday.com/articles/134777.php
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