The head of the World Health Organisation has declared that the H1N1 virus “has largely run its course” but warned that swine flu has not disappeared.

WHO Director-General Margaret Chan said that following a meeting of the agency’s emergency committee, she can say that “the world is no longer in phase 6 of influenza pandemic alert. We are now moving into the post-pandemic period".

However Dr Chan added that “ this does not mean that the H1N1 virus has gone away” and the WHO expects it to “take on the behaviour of a seasonal influenza virus and continue to circulate for some years to come”. She went on to say that “localised outbreaks of different magnitude may show significant levels of H1N1 transmission” and “this is the situation we are observing right now in New Zealand, and may see elsewhere”.

The WHO chief went on to say that the actions of health authorities in New Zealand, and also in India, “in terms of vigilance, quick detection and treatment, and recommended vaccination, provide a model of how other countries may need to respond in the immediate post-pandemic period”. She claimed that recently-published studies indicate that 20%–40% of populations in some areas have been infected by swine flu “and thus have some level of protective immunity”.

Dr Chan said that “pandemics, like the viruses that cause them, are unpredictable…so is the immediate post-pandemic period” She urged “continued vigilance”, noting that “based on available evidence and experience from past pandemics, it is likely that the virus will continue to cause serious disease in younger age groups”.

The WHO has been criticised in some quarters for over-reacting to the swine flu outbreak but Dr Chan is having none of it. She said “this pandemic has turned out to be much more fortunate than what we feared a little over a year ago [and] we have been aided by pure good luck”.

She noted that the virus did not mutate during the pandemic to a more lethal form, while resistance to Roche’s Tamiflu (oseltamivir) did not develop. Also, “the vaccine proved to be a good match with circulating viruses and showed an excellent safety profile”.

Dr Chan concluded by saying that “thanks to extensive preparedness and support from the international community, even countries with very weak health systems were able to detect cases and report them promptly. Had things gone wrong in any of these areas, we would be in a very different situation today”.

The WHO noted that at least 18,449 people have died worldwide since the outbreak began in April 2009, though the full death toll is likely to be higher once all the data is collated.