Research showed resistance to Tamiflu in the United States, Europe and Canada, due to the mutation of a strand of the influenza virus, actually weakened the virus and made it less contagious, The New York Times (NYSE:NYT) reported Friday.

Experts have not announced plans to discontinue the use of Tamiflu because reports of the mutated virus are few and the main influenza vaccine is till effective against it.

"Clearly, this is of global concern, but it is not a global problem now," influenza expert Dr. Frederick G. Hayden said.

Hayden said he does not believe the resistance developed from the use of Tamiflu treatment partly because no mutations have been reported in Japan, where it is used frequently.