The World Health Organization is inching closer to raising the infectious disease alert level for the novel H1N1 influenza outbreak to its highest level, indicating that a pandemic has arrived, but has delayed doing so in an effort to prepare national health organizations and populations for the impact of such an announcement, a top agency official said Tuesday in a telephone news conference.
The number of confirmed cases in Australia surpassed 1,200 on Monday, and the virus is no longer restricted to schools and other institutions there, suggesting that community-wide spread has begun.
Such a spread in two regions of the world -- it already has been observed in North America -- is the primary criterion for raising the alert level to Phase 6.
"One of the critical issues is that we do not want people to over-panic if they hear that we are in a pandemic situation," said Dr. Keiji Fukuda, assistant director general of WHO.
WHO officials worry that a pandemic declaration will lead people with mild illnesses to overwhelm emergency rooms.
"In earlier outbreaks, we have often seen that people who are in the category of being worried, but who are not particularly sick, have overrun hospitals," Fukuda said.
In the early stages of the current outbreak, he said, governments closed borders and issued travel restrictions. People stopped eating pork, pig herds were killed, and imports of pork were restricted by some countries.
"These are the kinds of potential adverse effects" that the agency is trying to avoid, he said.
Reporters pressed Fukuda about why, given the clear spread in Australia, the agency has not increased the alert level.
"We are really getting very close to that," he said. "We are working very hard to ensure that everyone is prepared for that."
In a separate talk with reporters, WHO Director-General Margaret Chan said she would confer with heads of governments around the world today to verify some of the reports the agency has received.
"Once I get indisputable evidence, I will make the announcement," she said.
In an effort to prevent overreaction to an increase in the alert level, the agency last week decided to divide Phase 6 into three tiers to indicate the severity of the pandemic. Barring changes in the next few days, the agency probably will indicate that the severity is at the lowest level when the alert stage is raised, indicating that the virus is spreading through populations, but that its effects remain relatively mild.
As of Tuesday morning, Fukuda said, there were 26,563 laboratory-confirmed cases of H1N1 flu, or swine flu, in 73 countries, with 140 deaths. In the United States, the most recent figures from the national Centers for Disease Control and Prevention showed 13,217 confirmed cases and 27 deaths.
Officials believe the number of cases, both in this country and worldwide, is actually much higher because many people have mild cases and are not tested.
Fukuda said that researchers have seen few, if any, changes in the virus since its emergence in Mexico early this year, and that it still remains susceptible to the antiviral drug Tamiflu.
But they are concerned that infections continue in North America and Europe, even though the traditional flu season has ended in the Northern Hemisphere.
"The disease patterns are not what we see from seasonal influenza," he said. That suggests the virus has greater capability for spread than does the seasonal flu.
Most of the infections have been in people younger than 60, which is also different from seasonal flu. That suggests, some experts said, that older people may have been exposed at some point to a different swine flu virus that has conferred some immunity.
About half of the people who have died of the virus were previously healthy, with no underlying medical conditions.
"That is one of the observations that has given us the most concern," Fukuda said. "We don't know why they died and why other people recovered."