The World Health Organization on Thursday acknowledged what many health experts have been saying for weeks: The outbreak of the novel H1N1 virus is a pandemic.
"The world is now at the start of the 2009 influenza pandemic," Dr. Margaret Chan, director-general of the WHO, said in a Geneva teleconference. "This virus is now unstoppable."
In a letter sent to WHO member countries, Chan said that she was raising the agency's infectious disease alert to Phase 6, its highest level, in recognition of the fact that the virus is undergoing communitywide transmission in Australia as well as in North America. Such spread in two distinct regions of the world is the primary criterion for raising the alert level.
But the agency said that the pandemic is only "moderate in severity" and cautioned against overreaction to the increased alert level.
The announcement marks the advent of the first global influenza epidemic in 41 years. The last one was the Hong Kong flu epidemic of 1968, which killed an estimated 1 million people worldwide.
The WHO had delayed declaring an H1N1 pandemic in part because some member nations had feared that it would trigger panic. Dr. Keiji Fukuda, assistant director-general, said Tuesday that the agency had used the time to conduct an educational campaign in an effort to minimize overreaction. It remains to be seen whether that effort will prove successful.
Most experts viewed the declaration as anticlimactic.
"It's been pandemic all along; nothing is different," said Dr. Charles Ericsson of the University of Texas Medical School at Houston. "Don't panic. The virus is still mild."
So far, the H1N1 flu, or so-called swine flu, pandemic this year has accounted for 28,774 laboratory-confirmed cases and 144 deaths in 74 countries, although health officials believe many times that number of people have been infected but have not been tested because their illnesses have been mild.
A normal seasonal flu outbreak kills about 250,000 to 500,000 people worldwide.
In most industrialized countries, the step up in the alert level will have little practical effect. In the United States, where there have been more than 13,000 cases, more than 1,000 hospitalizations and at least 27 deaths, "we have been reacting as though it were a pandemic already," said Dr. Anne Schuchat, director of the Centers for Disease Control and Prevention's National Center for Immunization and Respiratory Diseases. The same has been true in many other countries.
