Rick A. Bright, an immunologist at the U.S. Centers for Disease Control and Prevention said that all samples of seasonal influenza virus this year have developed resistance to adamantanes, the class of drugs which is used for the treatment for flu infection.
Drugs belonging to this class like amantadine and rimantadine are ineffectual for now and for the foreseeable future and shouldn't be used.
The findings were reported in the Journal of the American Medical Association. Amantadine and rimantadine were the pivotal drugs used against influenza A.
Statistics show that about 10-15% of the U.S. population suffers due to flu every year, and about 31,000 people die of it. Vaccination is considered the best strategy to prevent infection.
It was found that 91% of the 120 influenza a virus samples that were tested were resistant to these two drugs.
Presently a total of 209 influenza isolates (including the original 120) from 26 states across the United States were collected and analyzed. Overall resistance was found to be 92 %.
The researchers were very surprised at the speed with which the influenza strains develop the resistance. They feel that this is due to the widespread, over-the-counter and unregulated use of the drugs in other countries.
Tamiflu (oseltamivir) and Relenza (zanamivir) both the antiviral drugs belong to the neuraminidase inhibitor class of antivirals. The virus has not developed resistance against this class of drugs and hence can be used. But researchers fear that people will be using them more and might begin using them inappropriately and, with increased and inappropriate use, this will also become ineffective against the virus.
The researchers feel that there is an increased necessity for more energy and resources to be devoted to develop new antiviral drugs. In the end they conclude by saying that vaccines are the true way to protect oneself against influenza.