Note: Substantial material was added to this article at 6:15 p.m. US Central Time on the WHO's pandemic response and the role of public health going forward.

Aug 10, 2010 (CIDRAP News) – The head of the World Health Organization (WHO) today declared the H1N1 influenza pandemic over, saying worldwide flu activity has returned to typical seasonal patterns and many people have immunity to the virus.

"The world is no longer in phase 6 of influenza pandemic alert," said WHO Director-General Margaret Chan in a press briefing from Hong Kong. "We are now moving into the post-pandemic period. The H1N1 virus has largely run its course."

But she cautioned that the virus has not gone away and bears continued watching, commenting, "We expect the H1N1 virus to take on the behavior of a seasonal influenza virus and continue to circulate for some years to come."

The WHO's Emergency Committee met earlier today and recommended that the agency move to the post-pandemic phase, Chan said, adding that she fully supports the step.

The declaration comes almost exactly 14 months after the WHO moved to a full phase 6 pandemic alert on Jun 11, 2009, and about a month and a half after US health officials called off their public health emergency declaration on Jun 23. Many had expected the WHO to take the step months ago, but the Emergency Committee said in June and again in July that it was waiting for more information on the Southern Hemisphere's flu season.

Considerable H1N1 activity has been reported recently in India, New Zealand, and a few other places, with 942 new cases confirmed in India last week. But the current global picture is one of fairly typical seasonal flu activity, Chan said.

"Globally, the levels and patterns of H1N1 transmission now being seen differ significantly from what was observed during the pandemic," she said in a prepared statement. "Out-of-season outbreaks are no longer being reported in either the Northern or Southern Hemisphere. Influenza outbreaks, including those primarily caused by the H1N1 virus, show an intensity similar to that seen during seasonal epidemics.

"During the pandemic, the H1N1 virus crowded out other influenza viruses to become the dominant virus. This is no longer the case. Many countries are reporting a mix of influenza viruses, again as is typically seen during seasonal epidemics."

Chan added that recent studies show that 20% to 40% of populations in some areas gained some immunity to the H1N1 virus through infection. Further, "Many countries report good vaccination coverage, especially in high-risk groups, and this coverage further increases community-wide immunity," she said.

The WHO move is not expected to have a big impact on public health measures in the United States, the Centers for Disease Control and Prevention (CDC) said today, noting that the public health emergency declaration ended Jun 23.

In an e-mailed statement, the CDC said the only impact of the WHO step is that the CDC will stop sending weekly reports of flu activity to the WHO and the Pan American Health Organization, in accord with the International Health Regulations.

"There are no changes for the United States in terms of CDC's recommendations for the upcoming influenza season, and the United States is already proceeding with the understanding that the 2009 H1N1 virus is now part of seasonal influenza circulation," the agency said.

The trivalent flu vaccine for the upcoming flu season includes the pandemic H1N1 virus along with H3N2 and influenza B strains, the statement noted.

Chan, answering a reporter's question at the briefing, said, "I feel both [tired and happy], because this has been a long year of hard work, not just by colleagues in WHO, but by public health officials worldwide. We need to continue our vigilance and not be complacent."

Looking forward, she said, "It is likely that the virus will continue to cause serious disease in younger age groups, 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 hopefully the number of such cases will diminish."

She added that a small percentage of people infected during the pandemic, including young and healthy people, developed a form of severe viral pneumonia that is not usually seen during seasonal epidemics. "It is not known whether this pattern will change during the post-pandemic period, further emphasizing the need for vigilance," she said.

Chan reflected that the world was helped by "pure good luck" in this pandemic: "The virus did not mutate during the pandemic to a more lethal form. Widespread resistance to oseltamivir did not develop. The vaccine proved to be a good match with circulating viruses and showed an excellent safety profile."

Defending the WHO's response
Some critics, particularly in Europe, have accused the WHO of exaggerating the pandemic threat, with some arguing that the agency was improperly influenced by profit-hungry pharmaceutical companies. As she has previously, Chan today defended the WHO's record, but also acknowledged that it has learned some lessons from the episode, particularly concerning communication and flexibility.

Insisting that the WHO did not overreact to the virus, Chan said, "The WHO has been very consistent with its messages. Even at the outset and in subsequent messages, we mentioned we are dealing with a pandemic of moderate severity, and most people . . . will recover from the disease and many will recover without treatment."

At the same time, the WHO pointed out the virus's ability to cause severe disease in young adults, including some with no underlying health problems, and in pregnant women, she said, adding that she believes the agency has struck "the right balance."

As for lessons learned, Chan said in response to a question, "Number one, for WHO as well as for many of my member states, communication is a big challenge. Now we need to adapt the way we do communication, and learn how to work with social media and social networks."

Second, she said the WHO's pandemic preparedness guidelines were developed by experts "under threat of the H5N1 avian influenza virus, and that gave them the sense that collectively we should plan for the worst and hope for the best." One of the lessons is that "perhaps we need more flexibility in our future pandemic planning. We need to be able to have a best-case, an intermediate-case, and a worst-case scenario . . . to allow flexibility and adjustment as we track the evolution of the pandemic."

In a related development, the WHO today released the names of members of its Emergency Committee (see link below), as Chan promised it would do after the pandemic ended. The agency previously had withheld the names of all except the committee chair, saying it wanted to protect the panel from inappropriate pressures.

The WHO had been criticized for keeping the names secret and for its general policies on communicating about and managing potential conflicts of interest among its expert advisors. WHO defenders have said it would be very difficult to find top flu experts who have not done any consulting work for the pharmaceutical industry or received industry report for research.

In releasing the names of the committee members, the WHO also listed a declaration of interests. This shows that out of 15 members, four (plus one committee advisor) have done consulting work for vaccine manufacturers or other pharmaceutical companies and/or received industry support for research.

In other WHO comments today, Dr. Keiji Fukuda, special assistant to Chan for pandemic influenza, noted that the number of deaths due to confirmed 2009 H1N1 cases worldwide has reached about 18,500. The agency has said all along that the true number of H1N1-related is much higher, since many people who die of flu-related causes are not tested.

"W expect that over the next 2 years the more usual ways of counting deaths from this pandemic will be applied," he said. "We consider this current number to be minimum number of deaths. Over the next 2 years the numbers will be higher, but we don't know what they are now."

In her statement, Chan praised the recent responses of health officials in New Zealand and India to H1N1 activity as models of how countries should deal with the virus in the post-pandemic period. She cited their alertness, quick detection and treatment of cases, and promotion of vaccination.

She added later, "They maintained the vigilance at a time when many countries, I'm afraid to say, have become quite complacent."

The WHO today released a set of recommendations for disease surveillance, vaccination, and clinical management for the post-pandemic period (see link below).

Public health's ongoing role
In commenting on the WHO's action today, Jim Blumenstock of the US Association of State and Territorial Health Officials (ASTHO) said public health officials shouldn't let down their guard concerning flu.

"Even though we're in the post-pandemic phase, it doesn’t' mean we let our guard down. We still need to maintain a high degree of vigilance. We are literally weeks away from the next flu season, so the public health system still needs to be on alert to rapidly detect any outbreak that could occur and have programs and services in place to address those most vulnerable," said Blumenstock, ASTHO's chief program officer for public health practice.

He added that if current projections hold up, as many as 170 million doses of seasonal flu vaccine will be available this fall and winter, an unprecedented number. The public health system will need to work closely with private-sector physicians and others to promote safe and effective administration of the vaccine, he said.

Blumenstock commented that the value of public-private partnerships for public health has been one of the important lessons of the pandemic. For example, he said pharmacies, in their role as vaccinators and trusted community resources, made a very valuable contribution to the nation's response.

"The public health system should explore ways to capitalize on their resources, their respect and position in the community, to help us do a better job" in providing services, he said.

Another lesson of the pandemic is the benefits of and need for steady funding for public health, Blumenstock said. The nation's response to the pandemic was fueled in large part by emergency funding, he asserted, adding, "What we built a year ago is now being dismantled because the funding is no longer there."

While not advocating for maintaining "an army of national vaccinators as in the past year," Blumenstock said dependable funding is needed for maintaining surveillance, situational awareness, lab detection, and communication, especially with the goal of reaching disenfranchised groups.

See also:

Margaret Chan's statement

WHO press briefing page with access to recording of press conference

WHO recommendations for the post-pandemic period

WHO FAQ document on moving to a post-pandemic phase

List of WHO Emergency Committee members

Jun 3 CIDRAP News story "WHO advisors again hold at current pandemic phase"

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