The 16-year-old girl is the third person in the world to be diagnosed with a strain of H1N1 that is resistant to Tamiflu, a common antiviral drug that is the primary treatment for swine flu. But unlike the two other cases in Japan and Denmark, the teen did not take Tamiflu before she developed her symptoms, suggesting that the virus has developed a drug-resistant form that can pass between humans.
The girl was traveling from San Francisco to Hong Kong on June 11 when she set off a temperature-monitoring device in a Hong Kong airport. Officials say that she was feeling unwell before her trip, leading them to believe that she contracted the disease in the United States. The girl has since recovered.
In response to the girl's diagnosis, the Center for Disease Control and Prevention asked health departments across the country to submit more samples for testing, the AP reported.
The swine flu virus has caused well over 30,000 illnesses in the United States, including at least 170 deaths.