WHO declares flu pandemic

GENEVA -- The World Health Organization raised its alert on swine flu to the highest level on Thursday, in its first designation of a global pandemic in 41 years.

Calling further spread of the virus "inevitable," the organization's director general, Margaret Chan, said, "We are at the earliest days of a global pandemic."

The new H1N1 strain, she said, is "spreading easily from one person to another, and from one country to another" in more than one region of the world.

But the pandemic is "moderate" in severity, she noted, with the overwhelming majority of patients experiencing only mild symptoms and a full recovery, often in the absence of any medical treatment.

Scientists are painstakingly tracking its every movement.

"The virus is spreading under a close and careful watch," Chan said. "No previous pandemic has been detected so early or watched so closely."

The heightened alert came after an emergency meeting with flu experts that was convened after a sharp rise in cases in Australia, which reported 1,263 cases Thursday, and rising numbers in Britain, Japan, Chile and elsewhere. The declaration will trigger drugmakers to speed up production of a swine flu vaccine -- expected to take a minimum of four to six months -- and prompt governments to devote more money to containing the virus.

As the disease moves into the developing world, where rates of chronic disease are high and health systems typically poor, Chan said, "it is prudent to anticipate a bleaker picture."

The virus itself may also change quickly, becoming more lethal, she said, and even nations that have already experienced a rash of cases "should prepare for a second wave."

"The virus writes the rules, and this one, like all influenza viruses, can change the rules without any rhyme or reason," Chan said.

Unlike seasonal flus, which have taken their highest toll on the very young and the very old, Chan said, most severe cases of the new H1N1 virus have involved people between 30 and 50, while overall, the majority of all infections have occurred in people younger than 25.

About 2 percent of infections, Chan said, have resulted in severe illness, with rapid progression to pneumonia.