The U.S. Centers for Disease Control and Prevention is urging doctors to test suspected flu cases quickly to determine if it is the resistant H1N1 strain.

Only 11 percent of H1N1 flu cases last year were shown to be Tamiflu-resistant, compared to 99 percent of the cases this year, the New York Times reported Thursday. A publicist for Roche, the pharmaceutical firm that makes Tamiflu, noted the A(H3N2) and B viruses have shown no resistance.

"It's quite shocking," Dr. Kent A. Sepkowitz, director of infection control at the Memorial Sloan-Kettering Cancer Center, told the newspaper. "We've never lost an antibiotic this fast. It blew me away."