An epidemic is an outbreak of disease that is limited to a discrete geographic location, while a pandemic is an epidemic that has spread to many locations – typically multiple countries.
What is the swine flu?
The swine flu is a type of influenza virus usually found in pigs. The most common version is H1N1, and the current virus causing concern is a new variation of an H1N1 virus.
Swine flu does not typically pass to humans directly, but such transmission can occur. The current swine flu virus is concerning to health experts because it has shown the ability to pass from human to human.
How big a threat is this new swine flu virus?
Scientists around the globe are working hard to determine the threat level of the current swine virus. Right now, the virus is said to have "pandemic potential" because it is a new virus that can spread from person-to-person. But if it turns out the virus does not spread easily among people, the threat level will go down. Similarly, if it turns out the virus can spread easily among people, the threat becomes more serious and the virus is more likely to trigger a pandemic.
What defines a flu pandemic?
A flu pandemic occurs when a new virus emerges that can spread easily among people. When a flu virus mutates in such a way that it forms a novel version, it means people typically have little-to-no protection because their immune systems have no experience fighting the virus in the past. Flu viruses can spread quickly and potentially cause more severe illness when the population lacks immunity.
But all pandemics are not equally deadly. Some kill millions more people than usual, while others are roughly on par with seasonal flu in terms of deaths.
It is not possible to predict a pandemic in advance so health officials keep a close watch on viruses that have "pandemic potential" -- new viruses that have shown at least some ability to transmit to humans. The current H5N1 bird flu circulating in Asia is an example of a virus that has pandemic potential, but has not yet caused a pandemic.
What does a pandemic mean in terms of the death rate? Would it necessarily be severe?
Pandemics can vary quite a bit in severity. The 1918 pandemic killed many more Americans than an ordinary flu, while the 1968 version killed about 34,000 people -- about the same number killed each year by seasonal flu, according to CDC statistics.
The world generally experiences at least two flu pandemics each century. Historically, the 20th century saw 3 pandemics of influenza:
The 1918 influenza pandemic caused at least 675,000 U.S. deaths and up to 50 million deaths worldwide.
The 1957 influenza pandemic caused at least 70,000 U.S. deaths and 1-2 million deaths worldwide.
The 1968 influenza pandemic caused about 34,000 U.S. deaths and 700,000 deaths worldwide.
How does the swine flu spread?
Researchers are still investigating how easily the swine flu virus spreads, but experts say that transmission likely occurs the same way people pass on the usual flu: coughing or sneezing from sick people, shaking hands or otherwise touching persons who are infected with the virus, touching surfaces and objects that sick people have touched.
Can I get the swine flu from eating pork?
No, there are no signs that people can get the swine flu from eating pork.
How can I protect myself?
The CDC recommends the following steps to protect yourself from flu: