Experts Keep Wary Eye on Tamiflu-Resistant Swine Flu

July 9 -- WEDNESDAY, July 8 (HealthDay News) -- Health experts say they can't predict at this point how widely a new strain of swine flu resistant to the drug Tamiflu will spread, or how dangerous it might become.

"This is not unexpected, but it's very unpredictable whether this will end up spreading," said Dr. John J. Treanor, professor of medicine and of microbiology and immunology at the University of Rochester Medical Center in New York.

"There is certainly a potential for the novel H1 viruses to develop resistance to oseltamivir [Tamiflu] and for those resistant viruses to become widespread," he added. "Everyone recognizes that. That is the Achilles' heel of antiviral therapy and it's completely possible that we will see this with the novel H1N1."

"This is expected to a certain extent," agreed Dr. Manjusha Gaglani, associate professor of pediatrics at Texas A&M Health Science Center College of Medicine and a pediatric infectious diseases specialist at Scott & White Hospital.

Strains of the "regular" seasonal flu often become resistant to antiviral drugs but, generally speaking, antiviral resistance is less common with Tamiflu and a related antiviral drug, Relenza, than it is with two other drugs, amantadine and rimantadine, which the U.S. Centers for Disease Control and Prevention has recommended against using for seasonal flu.

Tamiflu is preferred over Relenza in general because it is easier to administer, Gaglani said.

So far, three people have been stricken in recent weeks by a resistant strain of the new H1N1 swine flu virus -- one in the United States, one in Denmark and one in Japan, according to published reports.

In all three cases, the illnesses were mild and all of the patients recovered.

Tamiflu is the main weapon available in the effort to prevent and treat H1N1 infections. As of yet, there is no vaccine for the H1N1 swine flu.

There is one troubling aspect to the resistance developments however: One of the people who fell ill had had no known contact with Tamiflu.