WHO ponders move to post-peak pandemic phase

Feb 11, 2010 (CIDRAP News) – With pandemic flu activity continuing to ease except in a few hot spots, the World Health Organization (WHO) said today it will convene its emergency group of experts at the end of the month to discuss a move to the post-peak phase of the pandemic.

Keiji Fukuda, MD, special adviser to the WHO director-general on pandemic flu, told reporters at a media briefing that though overall activity is declining in the Northern Hemisphere, it's clear that the pandemic H1N1 virus is still causing disease and deaths in many parts of the world.

For example, he said West African countries have reported very little pandemic flu activity, but the WHO recently received reports of community spread in Senegal. Fourteen cases have been confirmed there, where the disease has been mild with no reports of deaths, Fukuda said.

The pandemic virus is also active in parts of North Africa, Eastern Europe, and East Asia, he said, adding that the virus has so far been linked to 15,000 deaths worldwide.

The WHO will ask its emergency committee to consider if the pandemic activity has moved to the next phase, which Fukuda described as a transition period during which the pandemic continues, but the scientific evidence suggests that the worst is probably over.

The WHO's official explanation of the pandemic phases describes the post-peak period as a time when "levels of pandemic influenza in most countries with adequate surveillance have dropped below peak levels." It's the last phase before the post-pandemic period.

Fukuda said a question that often arises is why the WHO can't just declare that the pandemic is over. "Ending of a pandemic can't be considered on or off abruptly. Patterns are different in different countries, "he said, adding that designating a post-peak period is a way of helping national authorities look ahead and take the next planning steps.

In the meanwhile, the WHO is working on other influenza-related issues, Fukuda said. Next week experts will meet to discuss the flu strains that should be included in the Northern Hemisphere's 2010-11seasonal flu vaccine. The group will announce its recommendation at a public meeting on Feb 18.

Though Fukuda said he didn't want to predict if the group would recommend including the pandemic H1N1 strain, it is the most commonly isolated virus in the world and shows no sign of disappearing. "It's easier to guess that the experts will be looking at this virus as one to include," he said.

In September the WHO group recommended that the Southern Hemisphere's 2010 seasonal flu vaccine include the pandemic H1N1 virus instead of a current seasonal H1N1 strain. The recommendations were:

  • For pandemic H1N1, an A/California/7/2009-like virus (the same strain used in the pandemic vaccines now being made)
  • For H3N2, an A/Perth/16/2009-like virus
  • For type B, a B/Brisbane/60/2008-like virus

The WHO's recommendation for the 2009-10 Northern Hemisphere flu vaccine included a Brisbane-like influenza A H3N2 strain, but the US Centers for Disease Control and Prevention (CDC) has said in its influenza surveillance updates that most of the few H3N2 viruses it has analyzed are from the Perth-like group. (The CDC said in its latest surveillance update that it has characterized eight H3N2 viruses since Sep 1.) The CDC has said it is too early to predict if circulating seasonal strains will be a good match with the seasonal vaccine.

Fukuda said that though the pandemic H1N1 virus is the dominant flu strain globally, seasonal strains have not completely disappeared, with H3N2 present in some countries and more recently a fair amount of influenza B activity in China.

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