What's the difference between a seasonal flu outbreak and a pandemic?

A pandemic is defined as a pandemic where a new, deadly virus finds its way into human population. It is defined as a new or substantially unusual series of events that trigger widespread epidemics, as opposed to epidemics that follow a single event, such as a bad winter or an outbreak of a commonly used drug.

Does H5N1 count as a pandemic?

While the government did declare a pandemic in the 1970s when a H5N1 bird flu virus was widely transmissible between people, it’s not a pandemic because the case count remains low. No human-to-human transmission has occurred in this current outbreak in humans, meaning the virus doesn’t have the potential to spread through the air unless other people are infected.

How often are outbreaks like this?

While it isn’t clear why flu occurs frequently in any given year, yearly outbreaks in health care workers and others who are vulnerable to serious complications are fairly common. That’s why the Centers for Disease Control and Prevention recommends universal flu vaccination. It is important to note that flu happens during any season.

Are there any signs that a pandemic may be looming?

The World Health Organization is watching H5N1 closely. A strain of H5N1 recently sickened dozens of people, including two people who died. Experts say it was a hybrid of two separate H5N1 viruses; however, the strain originated from a bird flu in Africa.

Some infectious diseases become more common than others as populations age. Since H5N1 is now circulating in populations that are young and old, it is not clear whether a pandemic might be coming.