Scientists Fear New Resistant Flu Strains

By Daniel Welch Medill News Service

Controversy over the use of Tamiflu is growing as some experts say widespread use of the drug for seasonal flu could lead to resistant viral strains and public health experts worry about a shortage of a drug that has shown promise in fighting avian flu.

The Centers for Disease Control recommended physicians prescribe Tamiflu and a similar drug, Relenza, to treat the flu after announcing recently that two commonly prescribed older flu drugs will not be effective against this year’s predominant strain.

But some scientists advise against using Tamiflu for ordinary flu symptoms for fear that more resistant “super-viruses” will be created.

“We don’t want to force virus resistance,” said Northwestern University virologist Robert Lamb. “Instead of using them for the ordinary flu, we should save the drugs for when we really need them, like in a pandemic, especially when we have a perfectly good vaccine.”

The ineffectiveness of the common flu drugs amantadine and rimantadine could be due in part to the fact that they are available without a prescription in many countries, according to Lamb. Overused medications can sometimes prompt a virus to mutate, reducing the drug’s ability to neutralize the virus.

While Tamiflu and Relenza are effective against the flu because they use a different mechanism to attack the virus, they are much more expensive than the older drugs, which are no longer patented and are available in generic forms.

Nancy Donner, the director of pharmacy at Rush-Copley Medical Center in Aurora, said only “high-risk patients like the elderly, the very young, or people with serious health conditions” should use Tamiflu.

“For otherwise healthy people, taking the drug will help symptoms a little, but not a lot,” Donner said.

In addition, some public health officials are concerned that the more Tamiflu is taken for the ordinary flu this winter, the harder it will be to find if and when a pandemic hits. While flu kills 36,000 Americans a year, the CDC estimates an avian flu pandemic could kill as many as 8,700 people in Illinois alone in a 12-week period.

Countries around the globe have been scrambling to stockpile Tamiflu in preparation for a possible avian flu pandemic because early results showed the drug may have some success in treating the virus.

Terry Hurley, a spokesman for Tamiflu manufacturer Roche Pharmaceuticals, said the company sets aside Tamiflu supplies for seasonal flu and doesn’t anticipate a shortage of the drug.

To further complicate matters, a study published Thursday in Lancet, a British medical journal, suggests there is no evidence Tamiflu was effective in fighting the avian flu virus in the few patients who took the drug.

In a statement, Roche said it “fundamentally disagrees” with the study’s findings.

Flu viruses work by attacking a body cell and taking control of the cell’s machinery, directing the production of copies of itself. Those copies then leave the host cell and enter other cells, beginning the cycle again.

The older class of drugs such as amantadine and rimantadine combat the virus by preventing it from taking over the cell’s machinery.

In the CDC study the virus was resistant to these two drugs in 91 percent of test cases, an increase from last year’s resistance rate of 11 percent. In 2003, less than 2 percent of virus samples were resistant to the drugs.

“It could be a horrible sign of things to come,” Lamb said.

Tamiflu and Relenza can help to reduce the severity of the flu if taken within two days after symptoms begin because they work differently than the older drugs. After the virus takes control of the cell’s machinery, the new drugs prevent the virus from leaving the cell and infecting new cells.

Between 10 and 15 percent of Americans get the flu during a normal season, which usually lasts from November to April. This flu season has been relatively mild in Illinois, but people need to be reminded it’s only half over, said Cindy Gross, epidemiologist for the Kane County Health Department.

The best way to combat the flu, Gross said, is to get a vaccination.

“Some people think that since the holidays have passed and they didn’t get the flu, they’re out of the woods. That’s just not the case,” Gross said, adding that several local governments still have a supply of vaccine.