Transmission pathways for pathogenic avian influenza, subtype H5N1 (HPAI/H5N1), are summarized. Key findings are:
To date, the occurrence of human cases of HPAI/H5N1 has been very rare
The full extent of asymptomatic or subclinical infection with HPAI/H5N1 is unknown
Several epidemiological data gaps limit our understanding of risk factors for human infection.
HPAI Research Brief No. 15, 2009. 4 pp.