This document is an update to the World Health Organization (WHO) interim guidelines Infection prevention and control of epidemic- and pandemic-prone acute respiratory diseases in health care (2007). These updated guidelines incorporate the emergency guidance given in the WHO publication Infection prevention and control during health care for confirmed, probable, or suspected cases of pandemic (H1N1) 2009 virus infection and influenza-like illness (2009). The revision was informed by both evidence that has emerged since the first edition was published and the practical lessons learnt during the influenza pandemic in 2009.