Why is the flu so resistant to Tamiflu?

The CDC recently reported that 49 of the 50 H1N1 flu viruses were resistant to Tamiflu (oseltamivir).

Infectious disease physician Paul Sax shares some theories on why this is happening, and cites a virologist who says “it might be the result of preventive programs in nursing home-type settings during flu outbreaks.”

Tamiflu is normally recommended during flu outbreaks in high-risk populations, like nursing homes or other long-term care facilities. Given the resistance, Dr. Sax recommends a trend towards zanamivir or rimantadine.

How long will it be before the virus becomes resistant to these other drugs? Will we face a future where “we’ll be using nothing but TLC, which is kind of where we were several years ago?”

Comments

Anonymous
Tamiflu stinks anyway. Barely better than placebo. Several plans my way, including medicaid, require prior authorization. By the time that is obtained, any potential benefit is gone.
Anonymous
Why is it that any physician sponsored CME there is Always some authoritative clown admonishing physicians about overuse of antibiotics/antivirals? Yet, to my knowledge, there has never been a direct dna link between resistant strains and their use in humans or a human source. There has of course been a direct link with vanco resistant staph and Danish cattle.
Why is Tamiflu not effective? Chinese farmers have been using it in their duck feed for years. Gee what a surprise! Can you guys talk plasmids, e. coli and gut flora? Their farmers’ options are having a flock contaminated with a single bird with bird flu and the subsequent destruction of their business, or giving low doses, long duration in their feeds.
Hmmm.. Vermont farmers have been giving Cipro to their dairy cattle for about 18 years. Oh, and western horses get doxycycline in their feed.
Please stop the blathering about using amoxicillin for little johnny’s ear infection ( high dose, short duration) and grandma mary’s Tamiflu until you medical types start talking to the department of agriculture (multinationally by the way)to amend their ways.
Rogue Medic
Anonymous 12:53,
Yes, there are other problems with the development of resistance.
No, there is no requirement that we only address them in order of volume.
Prescribing antibiotics for viral illnesses is voodoo medicine. Encouraging tolerance of this pseudoscience is dangerous.
Congratulations to the CME sponsors, who are opposing this superstitious practice.
Yes, we should also be working to decrease the use of antibiotics in other areas. That does not mean those are the only areas that need attention.
Anonymous
rogue,
you are right there is no requirement about addressing the issue as a function of volume. but lets put it into perspective. 80% of antibiotic/antiviral production is given to animals. there are 2.5 billion ducks in china alone which receive Tamiflu daily. compare that with the author’s issue of about the 100 residents of a nursing home who may receive the same drug (even inappropriately). Stopping all antibiotic/antiviral use in humans will not change the probability of resistant bugs if it is still used in agriculture. on the other hand, stopping all use in agriculture has a much higher probability of stopping resistance regardless what is done in the human population.
thinking that this is a problem for the health care industry to solve is naive and arrogant. for at least 20 years we have been hearing the experts pontificate about overuse of human antibiotic usage, yet not a peep about the actual cause of resistance (as the cited article attests ). if the medical experts want to solve the problem, they can, just not in their sphere of influence.
prescribing antibiotics for viral illness is of course voodoo medicine. however, much of what the medical profession does is voodoo medicine as outcome research is in its infancy. the real question that i propose is not whether the inappropriate use of antibiotics/antivirals in human populations does any good, but rather is there any actual proof that it does any harm. if not, then the experts can stop pontificating and solve bug resistance at its source.
Rogue Medic
Anonymous,
It has been quite a while since I took microbiology. I have forgotten a lot of the details, but I believe the following is accurate.
Drug resistance that affects patients locally is of local origin. It does not just come from farm animals. We should be trying to decrease the amount of antibiotics given to farm animals here and abroad, but that is not a good reason to avoid trying to minimize the overuse of antibiotics in human patients.
I am obviously not familiar with the research on this, but why should we believe that use of antibiotics in humans, affecting bacteria that appear to thrive in humans, does not by pass a lot of the defenses of the human body? While the scale of farm bred resistant bacteria is much larger than in humans, the specificity of the human bred resistant bacteria should be of concern. This, if my reasoning is correct, suggests that the use in humans would have a greater effect on the incidence of resistant bacteria in humans. Or, at least a significant effect.
I would not take the position that one is good, while the other is bad. Both need to be addressed. Would you want to be treated by a physician, who feels it is appropriate to treat viral infections with antibiotics? What other misinformation is there in his/her head?
We do not need evidence of harm to stop using a treatment, we need evidence of benefit to advocate for treatment. Too much of medicine does not have any evidence of benefit. This is bad medicine.
You stated earlier, Yet, to my knowledge, there has never been a direct dna link between resistant strains and their use in humans or a human source.
At some point I will have to look for some research on this. Do you know of any review papers that look at a lack of evidence of resistance developing in a human population? Or some suggestions of key words for a PubMed search? I always have problems with these lack of benefit searches.
Rishi
There was actually a study done showing how Tamiflu accumulates in the environment, namely the water supply, and causes a selective pressure to favor the resistant strains of flu. Another wonderful example of how terrible over-prescribing can potentially be.

Why is the flu so resistant to Tamiflu?

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