World Health Organization: Geneva

The epidemiology of influenza A(H7N9) virus among animals, including the main reservoirs of infection among animals and the extent of geographic spread, is not yet established. So far, there is no evidence of sustained human-to-human transmission. However, the two possible family clusters suggest that limited human-to-human transmission may occur where there is close contact between cases and other individuals, as occurs in families and, potentially, healthcare settings. Moreover, the genetic changes seen among these viruses suggesting adaptation to mammals is of concern, and further adaptation may occur.

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