The CU-Boulder Pandemic Flu Planning website

Medical experts at the World Health Organization believe the world is due for its next flu pandemic in the near future. The first step in preparing for this possibility is learning what a pandemic flu is and understanding how the influenza strains that might cause one differ from the seasonal flu that strikes each year.

"Seasonal flu hits every year during the fall and winter months," said Sandra Sonoda, RN, infection control nurse at Wardenburg Health Center. "It has a sudden onset, and people generally have a bad headache, body aches, a fever of over 100.5 degrees and a sore throat. They feel ill, generally so bad they can't get out of bed, and some may develop a cough or pneumonia as a result of the infection. The elderly and the very young are at the most risk, with a mortality rate in the United States of around .008 percent."

The H5N1 avian influenza virus is considered the most likely pandemic flu candidate, though it is currently restricted for the most part to bird populations in Asia and Europe. World health officials are watching the virus to see if it mutates into a form easily transmitted from human to human, at which time the risk of it causing a flu pandemic would rise dramatically.

"Right now the H5N1 virus is a bird flu," said Sonoda. "It spreads via birds. It's highly toxic to birds, leading up to a better than 99 percent mortality rate among chicken flocks. So the people who are most at risk for avian flu are those who are in close contact with domestic poultry or wild poultry. We don't know how many total people have been infected with H5N1 to date, but the reason we're concerned is that, of those infected who were sick enough to seek medical care, the mortality rate is about 56 percent."

According to Sonoda, an influenza outbreak becomes a pandemic when the following three conditions are met: 1) a strain of the virus that humans have no immunity for is introduced; 2) it causes serious illness and death; and 3) it spreads easily and rapidly through the human population.

"The problem with H5N1 is that two of those conditions have been met. That's why we're watching this flu really closely," said Sonoda. "If the virus undergoes a shift in its genome, the entire human population will be at risk for this infection, though so far it is not efficiently spread among humans."

To learn more about the differences between seasonal, avian and pandemic flu—including easy ways to help prevent the seasonal flu this year and steps you can take to prepare for a flu pandemic—visit the university's Pandemic Flu Planning website.