What is a pandemic?
A pandemic may occur when three conditions have been met: a new influenza virus subtype emerges; it infects humans causing serious illness; and it spreads easily and is sustainable among humans. The H5N1 virus meets the first two conditions. The risk that it will acquire the ability to have efficient and sustained human-to-human transmission is present as long as opportunities for human infections occur. These opportunities will persist as long as the virus continues to circulate in domestic birds, perhaps for years to come.
Every 20 years or so, an influenza virus strain appears that is dramatically different from the other members of its family. This strain may be very virulent, and make people sicker than usual. When this major change occurs a worldwide epidemic, called a pandemic, almost inevitably follows because influenza spreads very quickly, especially with modern transportation methods such as airplanes. Few people have antibodies that are effective against the new virus. This virus has not yet been included in the vaccine. Until now, pandemics have always been caused by a type A-virus.
A pandemic is a global disease outbreak. A flu pandemic occurs when a new influenza virus emerges for which people have little or no immunity, and for which there is no vaccine. The disease spreads easily person-to- person, causes serious illness, and can sweep across the country and around the world in very short time. It is difficult to predict when the next influenza pandemic will occur or how severe it will be. Wherever and whenever a pandemic starts, everyone around the world is at risk. Countries might, through measures such as border closures and travel restrictions, delay arrival of the virus, but cannot stop it. Health professionals are concerned that the continued spread of a highly pathogenic avian H5N1 virus across eastern Asia and other countries represents a significant threat to human health. The H5N1 virus has raised concerns about a potential human pandemic because: It is especially virulent It is being spread by migratory birds It can be transmitted from birds to mamm
