Paradigm Shift Intervention Monitoring
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Commentary
Camper to Camper
Transmission of
Tamiflu Resistant H1N1
Recombinomics
Commentary 22:21
September 10, 2009
A second previously healthy adolescent girl, who resided in the same cabin as patient A, began oseltamivir chemoprophylaxis at a dose of 75 mg daily on July 7 after exposure to patient C. On July 10, patient B left camp for a home visit during the break between camp sessions. The next day, while at home, she experienced onset of fever (101.9ºF [38.8ºC]), sore throat, and cough. She continued to engage in normal activities while ill, including visiting a shopping mall and movie theater. She returned to camp for the second session on July 12 with fever, headache, cough, malaise, and myalgias. On July 12, a rapid influenza detection test was positive for influenza A.
On August 14, CDC testing of viral RNA detected H275Y and I223V mutations
The above comments are from tomorrow's MMWR and describe two summer campers who were infected with oseltamivir (Tamiflu resistant) pandemic H1N1 while on prophylactic Tamiflu. Since the campers shared the same cabin, and developed symptoms four days apart, it is likely that one camper infected the other. The scenario is also supported by the detection of the same rare marker, I223V, which has not been reported in other human or swine pandemic H1N1 isolates, but is present in two avian H1N 1isoaltes (see list here).
The report of this human to human transmission follows a similar report in Hong Kong, reported yesterday. In that case a younger (32M) brother was treated with Tamiflu, and his older brother (38M) developed symptoms and was positive for Tamiflu resistant pandemic H1N1 even though he had no Tamiflu exposure. Other family members were also infected, and like the younger brother, were Tamiflu sensitive, suggesting the index case was infected with a mixture and the brother was infected by the H274Y positive version, while other family members were infected with wild type H1N1.
These resistant sequences are most easily detected in patients taking prophylactic Tamiflu, because they are being monitored and symptoms while on Tamiflu raises suspicions of resistance. The Hong Kong case was discovered because of an aggressive surveillance program, which detected H274Y in an earlier traveler from San Francisco , who also had no Tamiflu exposure increasing concerns of transmission by evolutionarily fit H1N1 with H274Y.
These repeated outbreaks of H274Y on multiple genetic backgrounds of pandemic H1N1 raise concerns that the fixing of H274Y in seasonal flu, which was driven by recombination and genetic hitchhiking, will be repeated in pandemic H1N1 in the near future.
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