January 09, 2009
Mutating flu kicks drug's butt
The International Herald Tribune has some disturbing news, coming on the heels of reports out of China that Bird Flu is claiming more victims.
Virtually all the flu in the United States this season is resistant to the leading antiviral drug Tamiflu, and scientists and health officials are trying to figure out why.
[...]
Last winter, about 11 percent of the throat swabs from patients with the most common type of flu that were sent to the Centers for Disease Control and Prevention for genetic typing showed a Tamiflu-resistant strain. This season, 99 percent do.
"It's quite shocking," said Dr. Kent Sepkowitz, director of infection control at Memorial Sloan-Kettering Cancer Center in New York. "We've never lost an antimicrobial this fast. It blew me away."
[...]
In response, the CDC issued new guidelines two weeks ago. They urged doctors to test suspected flu cases as quickly as possible to see if they are influenza A or influenza B, and if they are A, whether they are H1 or H3 viruses.
The only Tamiflu-resistant strain is an H1N1. Its resistance mutation could fade out, a CDC scientist said, or a different flu strain could overtake H1N1 in importance, but right now it causes almost all flu cases in the country, except in a few mountain states, where H3N2 is prevalent.
Complicating the problem, antiviral drugs work only if they are taken within the first 48 hours. A patient with severe flu could be given the wrong drug and die of pneumonia before test results come in. So the new guidelines suggest that doctors check with their state health departments to see which strains are most common locally and treat for them.
"We're a fancy hospital, and we can't even do the A versus B test in a timely fashion," Sepkowitz said. "I have no idea what a doctor in an unfancy office without that lab backup can do."
If a Tamiflu-resistant strain is suspected, the disease control agency suggests using a similar drug, Relenza. But Relenza is harder to take — it is a powder that must be inhaled and can cause lung spasms, and it is not recommended for children under 7.
[...]
Alternatively, patients who have trouble inhaling Relenza can take a mixture of Tamiflu and rimantadine, an older generic drug that the agency stopped recommending two years ago because so many flu strains were resistant to it. By chance, the new Tamiflu-resistant H1N1 strain is not.
[...]
Dr. Henry Niman, a biochemist in Pittsburgh who runs recombinomics.com, a Web site that tracks the genetics of flu cases around the world, has been warning for months that Tamiflu resistance in H1N1 was spreading.
He 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, he 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, he 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.
Here's the killer 'graf, as it were, buried at the very end of the story:
[W]hile 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 pandemic strain, as many experts recently feared it would, it still could — and Tamiflu resistance in that case would be a disaster.
A further worry -- as I noted below -- is the reluctance of most Americans to voluntarily quarantine themselves when they feel ill, making the spread of these would-be pandemics disturbingly likely.
Anyone who works in the courthouse is exposed to every conceivable strain of illness known to humanity; attorneys have been known to mysteriously come down with hepatitis after spending time with their incarcerated clients in face-to-face whispered conferences during trials and hearings.
I've never passed up a chance to get my annual flu vaccination since I started practicing law; it's sobering to think that there may be no protection available from the new breed of rapidly mutating superbugs.
Posted by Mike Lief at January 9, 2009 11:15 AM
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