Swine Flu Outbreak May Spark UN Agency Review of Pandemic Alert WHOs alert level is at level 3, meaning there is no, or very limited, human-to-human transmission of a potential pandemic virus. Officials at the agency have said the global spread of the H5N1 bird flu virus since 2003 has put the world closer to another influenza pandemic than at any time since 1968, when the last of the previous centurys three pandemics occurred.Pandemic AlertWHO uses a six-step alert system to tell the world what preparations to take in response to a pandemic. Flu can spread quickly when a new strain emerges because no one has natural immunity and a vaccine takes months to develop. The 1918 Spanish Flu pandemic, which killed as many as 50 million people, began when an avian flu virus jumped to people, doctors said.Teams of disease investigators have been sent to California and Texas to trace how the malady has spread, and the U.S. offered to send scientists to Mexico, said the CDCs Besser. U.S. hospitals are being asked to collect samples from patients with flu-like symptoms, said Schaffner, chief of preventive medicine at Vanderbilt, in a telephone interview yesterday.They are asking us who work in hospitals to go to our emergency rooms and our pediatric wards to gather specimens and start testing them, Schaffner said. This has a sense of urgency about it.