June 3 (Bloomberg) — Swine flu, becoming entrenched in Australia and Chile, will prompt the World Health Organization to declare the first influenza pandemic in 41 years, said three people familiar with the agency’s plans.

Margaret Chan, the WHO’s director-general, will make the announcement sometime in the next 10 days, said the people, who spoke on condition of anonymity because the deliberations are private. The agency, having spent the past five years alerting the world to the dangers of a pandemic, is now looking for a way to declare one without causing panic.

Chan has to navigate a delicate path between raising alarm about a virus that in most cases causes little more than a fever and a cough, and underestimating a bug that could kill millions. Moving to the top of WHO’s six-step pandemic scale may spur some countries to restrict travel, ban public events and adopt other measures that aren’t needed for mild flu, worsening the deepest economic slump since the Great Depression.

“The formalization of an influenza pandemic does have cascading consequences,” said Michael Leavitt, former U.S. health and human services secretary. “The decision ought not to be taken lightly,” Leavitt said in an interview. “The system of evaluating and triggering different levels of alert is still being refined at the WHO.”

Chan and colleagues spent 7 hours on June 1 consulting experts and public health officials from 23 countries on how to explain that swine flu is global, but not severe.

Severity Scale
Following the discussion, the WHO is considering a three- point scale to denote different levels of severity once phase 6 has been declared, Keiji Fukuda, the agency’s assistant director-general of health security and environment, said on a conference call with reporters yesterday.