"THE threat of an influenza pandemic is, at present, one of the most significant public health issues our nation and world faces." -- Dr. Andrew C. von Eschenback, commissioner of the U.S. Food and Drug Administration, April 2007
"We know that a pandemic will eventually occur. We always say it's not a question of if; it's a question of when." -- Dr. Julie Gerberding, director of the Centers for Disease Control and Prevention, April 2007
A year ago, concerns about pandemic flu were running high, with the threat of an outbreak making newspaper headlines and television newscasts. Now the specter of this threat has largely faded from the public mind -- as if the risk has passed. But public health experts remain as concerned as ever about the possibility of an outbreak.
"We can't predict when an influenza pandemic will occur or which virus will cause it," says Nancy Cox, director of the influenza division at the CDC. "However, we can be almost 100% certain that there will be one."
It's that kind of conviction that's prompting public health experts to encourage people to prepare for an outbreak. Complacency needs to be replaced with knowledge and action.
Flu pandemics are caused by influenza A virus -- the same virus responsible for the seasonal flus we suffer each winter. There's a reason we can catch flu again and again: Many different strains of the virus exist, and new forms are always emerging.
The virus is constantly undergoing subtle changes, called mutations, in its genetic material. These small changes are what make the seasonal flu viruses slightly different every winter and why a new flu immunization is required each year.
Occasionally, the virus undergoes a dramatic shift and a truly novel viral strain is created -- one with pandemic potential. Because there is little or no immunity to the new form of the virus, it spreads easily and rapidly from person to person, and its global spread is considered inevitable.
Unfortunately, it is currently impossible to predict when a pandemic will break out and which viral strain will cause it. "The influenza virus is highly unpredictable," Cox says. It is also difficult to anticipate the magnitude of the outbreak. Experts estimate that a pandemic of relatively low severity could potentially cause 90,000 U.S. deaths if appropriate interventions are not made; in the case of a very severe pandemic, this number increases dramatically -- to more than 1.8 million.
