Scientists are baffled over the case of two bird flu patients in Vietnam. Both patients died after developing resistance to Tamiflu, the drug that is being stockpiled in case of a flu pandemic.

The girls had received early and aggressive treatments with Tamiflu and had received the recommended doses, according to an Associated Press report. Doctors now think they may need to rethink dosages. Lower amounts may promote resistance by allowing viruses or bacteria to mutate and make a resurgence, according to the press accounts.

Concern about Tamiflu surfaced in October when doctors discovered bird flu in a 14-year-old girl who had been given low doses of the drug as she cared for her brother who had been diagnosed with bird flu.

In coming months the World Health Organization and the National Institutes of Health will launch an experiment with drugmakers on humans. They want to know if doubling the dosage of Tamiflu is more effective.

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