EID Journal Home > Volume 17, Number 6–June 2011

Volume 17, Number 6–June 2011

Human Infection with Avian Influenza Virus, Pakistan, 2007

Human infection with avian influenza (H5N1) virus raises concern for the possibility of a pandemic. We report 20 cases, which ranged from asymptomatic to fatal, in Pakistan in 2007.

These cases indicate human-to-human-to-human transmission of this virus, and the number of cases may be higher than realized.

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Several features of the outbreak are unusual or give cause for concern: human-to-human-to-human transmission, possible nosocomial transmission, occurrence of mild and asymptomatic cases, and difficulties of establishing laboratory confirmation of likely and possible cases (which also prevented genotypic matching of specimens from primary and putative secondary cases).

Taken together, these features suggest that current surveillance might undercount the extent of human infection with influenza (H5N1) virus and that human-to-human transmission might possibly be associated with less severe disease.

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