The flu that will trigger a human pandemic, which experts agree will eventually happen whether or not it's related to the deadly H5N1 bird flu circulating now, is unknown.
"There is no H5N1 pandemic so there can be no pandemic vaccine," said Dr. Daniel Lucey, co-director of the Biohazardous Threats and Emerging Diseases graduate program at Georgetown University.
Public health workers are monitoring the bird flu for signs of changes that would allow it to pass from person to person.
Especially in Southeast Asia, chicken and other poultry mingle freely with people, raising the risk of infection. The virus, responsible for at least 60 deaths and 130 infections in people, must undergo further mutation or mix with a human flu in order to spread easily among people.
An American test vaccine against the H5N1 bird flu is what Lucey calls a "pre-pandemic vaccine" -- and that, he said, "assumes that H5N1 will be responsible for a pandemic." Either way, global outbreaks of flu, he continued, usually come in two waves. The 1918 bird flu, which killed between 20 and 50 million people, and the 1957 outbreak both followed this pattern.
Despite advances in science since the last outbreak, modern global travel patterns could take the virus to every corner of the world within a matter of days. Questions about the next pandemic, such as its lethality and when exactly it will strike, elude researchers. "No one knows for sure. It's not knowable," Lucey said at a recent flu policy conference hosted by Georgetown.
Dr. Kumnuan Ungchusak, director of the Bureau of Epidemiology in Thailand, suggested the best way to prevent a human pandemic is by surveillance and communication among local health officials and governments -- a network of surveillance and rapid response teams to assess each potential case of bird flu.
Thailand has 850 district health centers, each with enough antiviral capsules to treat two patients, Ungchusak said. The Health Ministry, however, has a central stockpile of close to a million capsules and growing.
Nations are frantically working to increase their stockpiles of the antiviral Tamiflu -- a drug used to treat, but not prevent bird flu -- but efforts may prove futile if the virus mutates significantly or becomes resistant to the drug.
The World Bank recently announced a $500 million loan program to help poor Southeast Asian countries that are struggling to ward off a looming outbreak.