The World Health Organization announced on Tuesday the end of the swine flu, AH1N1. The world is no longer in the 6th stage of pandemic alert, WHO general director Margaret Chan declared.

The world is now in the post-pandemic period. Based on knowledge about past pandemics, the H1N1 (2009) virus is expected to continue to circulate as a seasonal virus for some years to come.

While the level of concern is now greatly diminished, vigilance on the part of national health authorities remains important. Such vigilance is especially critical in the immediate post-pandemic period, when the behaviour of the H1N1 (2009) virus as a seasonal virus cannot be reliably predicted.

For example, it is likely that the virus will continue to disproportionately affect a younger age group, at least in the immediate post-pandemic period. Groups identified during the pandemic as at higher risk of severe or fatal illness will probably remain at heightened risk, though the number of such cases could diminish. In addition, a small proportion of people infected during the pandemic developed a severe form of primary viral pneumonia that is not commonly seen during seasonal epidemics and is especially difficult to treat. It is not known whether this pattern will continue during the post-pandemic period, further emphasizing the need for vigilance.

WHO is today issuing guidance on recommended activities during the post-pandemic period, including advice on epidemiological and virological monitoring, vaccination, and the clinical management of cases.

National health authorities are reminded that cases and local outbreaks of H1N1 (2009) infection will continue to occur, and in some locations, such outbreaks could have a substantial impact on communities.