WHO Rethinks Swine Flu Pandemic Criteria

WHO Says It Will Consider Signals of Virus Threat to People, Not Just Spread of Virus

Medically Reviewed by Louise Chang, MD on May 22, 2009

May 22, 2009 -- The World Health Organization today said it will reconsider its standards for deciding when to declare the H1N1 swine flu a pandemic.

That decision comes at the urging of the world's health officials, who have been meeting in Geneva, Switzerland, at the headquarters of the World Health Organization (WHO).

The WHO has pandemic alert phases that range from 1 (little risk of a pandemic) to 6 (a pandemic is under way). Those phases are all about how the virus is spreading, not about the severity of the illness that the virus is causing.

The WHO has set the pandemic alert level at phase 5 for swine flu. That's one step shy of a pandemic.

This week in Geneva, health officials asked the WHO to think about more than the spread of the H1N1 swine flu virus in deciding whether to declare a swine flu pandemic.

Today, WHO officials say they would do just that.

"We have taken this under advisement," Keiji Fukuda, MD, assistant director-general for health security and environment at the WHO, said today at a news conference. "We will think this through."

Walking a 'Fine Line'

Fukuda stressed the importance of flexibility in deciding whether to move from the current pandemic alert level of phase 5 to phase 6.

On the one hand, the H1N1 swine flu virus continues to spread. But on the other hand, most cases haven't been severe, and Fukuda says that health officials told the WHO this week that when the WHO raises its pandemic alert levels, people become alarmed.

The WHO is "trying to walk a very fine line between not raising panic not becoming complacent," Fukuda says.

The point of the pandemic alert phase system is to help countries prepare, and many countries have done that for swine flu, Fukuda notes.

But "there is nothing like reality to tell you if something is working or not," Fukuda says. "Rigidly adhering to something which is not proving to be useful would not be helpful to anybody."

The WHO hasn't settled on its new criteria for moving from phase 5 to phase 6.

Fukuda said the basic idea will be to look for "signals" that the virus is becoming more dangerous to people. Those cues might include greater severity of illness or changes in how the virus is behaving.

Latest Swine Flu Numbers

The WHO today reported that it has received reports of 11,168 people in 42 countries with lab-confirmed H1N1 swine flu infection, including 86 people who have died.

The CDC today said that it has received reports of 6,552 people in 48 U.S. states with confirmed or probable swine flu, including nine people who have died.

The CDC estimates that as many as 100,000 people in the U.S. have the swine flu virus. The number of lab-confirmed cases "may represent about one in 20 [cases] of actual illness," Anne Schuchat, MD, interim deputy director for the CDC's science and health program, said in a press conference today.

Schuchat said that nationally, the number of cases "seems to be falling" but is rising or still high in some areas. She cautioned against becoming complacent and urged people to keep washing their hands, cover their coughs or sneezes, and stay home when sick.

"We don't want people to think we're out of the woods yet," said Schuchat, noting that it's not clear yet if the virus will stay in circulation this summer or worsen in the fall.

In other swine flu news, Health and Human Services secretary Kathleen Sebelius today announced that she is directing about $1 billion in existing funds to prepare to make an H1N1 swine flu vaccine.

That money will fund clinical studies that will be done this summer and for commercial-scale production of two potential vaccine ingredients for the pre-pandemic influenza stockpile.

Show Sources


Keiji Fukuda, MD, assistant director-general for health security and environment, World Health Organization.

Anne Schuchat, MD, interim deputy director for science and public health program, CDC.

World Health Organization.


News release, U.S. Department of Health and Human Services.

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