Tamiflu-Resistant Swine Flu Found in Canadian Father
Nov. 12 -- WEDNESDAY, Nov. 11 (HealthDay News) -- Researchers report that a father in a Canadian family developed a strain of the H1N1 swine flu that was resistant to the antiviral Tamiflu, after being given the drug to prevent the disease.
To date, the World Health Organization has reported some 45 cases of H1N1 swine flu that were resistant to Tamiflu, which is why the U.S. Centers for Disease Control and Prevention and others caution against using Tamiflu to prevent the disease in people who are symptomless.
"We have a person who was taking post-exposure prophylaxis with Tamiflu, probably at the time he was already incubating the virus, but before symptoms developed," said lead researcher Dr. Guy Boivin, of the Centre Hospitalier Universitaire de Quebec, in Quebec.
According to the report, when the father's 13-year-old asthmatic son was hospitalized with H1N1 swine flu, other family members were given a reduced dose of Tamiflu to prevent them from getting the disease. These included the 59-year-old father, who suffered from chronic obstructive pulmonary disease (COPD), his 50-year-old wife and two teenage daughters.
Within a day the father developed flu symptoms, but he did not see a doctor for eight days. A test of his virus showed that it was resistant to Tamiflu. None of the other family members developed flu. The father recovered from the flu, according to the report in the Nov. 11 online edition of the New England Journal of Medicine.
The mutated strain of H1N1 swine flu remained susceptible to another antiviral, Relenza, Boivin added.
The family's experience was a good setting for resistance to emerge, Boivin said. When someone has the H1N1 swine flu, Tamiflu is given twice a day for five days. But when the drug is used to prevent the disease, it is given only once a day for 10 days, he explained.
Since the father was most likely already infected with swine flu, the dose of Tamiflu he received was ineffective at stopping the virus and low enough to allow the virus to develop resistance to the drug, Boivin said.
