The H1N1 pandemic is not yet over although its most intense activity has passed in many parts of the world, the World Health Organization said on Thursday after a review of the flu outbreak by independent experts.
The WHO emergency committee, composed of 15 external advisers, said it remained critical for countries to maintain vigilance concerning the pandemic, including necessary public health measures for disease control and surveillance, WHO Director-General Margaret Chan said in a statement.
"We're still in the pandemic," WHO spokesman Gregory Hartl told Reuters.
Chan said that pandemic flu activity was expected to continue, and the committee would meet again by mid-July to review the status of the outbreak once more data from the winter influenza season in the southern hemisphere was available.
The panel met on Tuesday, but Chan had delayed the announcement until Thursday as the committee, whose members were spread around the world for the meeting by teleconference, put the final touches to the wording of their recommendation.
Chan's decision, based on the committee's recommendation, means that the outbreak, widely known as swine flu, remains at phase 6 on the WHO's pandemic scale, which has been at the top level of 6 since June 2009.
The next meeting will decide to recommend whether to retain that level, declare the pandemic has passed, or move into a transitional "post-peak" phase.
The U.N. agency's guidance on whether a disease constitutes a pandemic determines how its 193 member governments handle an outbreak, including stockpiling vaccines and antivirals.
WHO experts say that the virus remains a threat to some vulnerable people, notably pregnant women, young children and those with respiratory problems, and such groups would continue to need vaccinations.
"It is predicted that H1N1 will continue to be the primary or overwhelming virus among influenza viruses for quite a while," Hartl said on Tuesday. "Pandemic or no pandemic, H1N1 will still exist. If there is no pandemic, it means that H1N1 is behaving like a normal flu virus."
The WHO has been accused of exaggerating the dangers of the H1N1 outbreak, which emerged in April last year.
Symptoms suffered by most people infected with the virus, have been mild. But WHO experts fear it could spread easily among people if it were to mutate into a more dangerous or lethal form.
Laboratory tests have confirmed more than 18,000 deaths from H1N1 infection, according to WHO figures, but the actual global death toll is much higher and will take at least a year after the pandemic ends to establish.
The virus is currently most active in parts of the Caribbean and Southeast Asia, and activity in Africa is low or sporadic.
The emergency committee has been waiting for signs of how the virus is developing in the southern hemisphere winter before making a full pronouncement on its state.
Chan usually follows the recommendations of the committee, all of whose members except its chairman, Australian professor John Mackenzie, are anonymous to protect them from undue influence.