Swine Flu FAQ

How severe is swine flu?

The severity of cases in the current swine flu outbreak has varied widely, from mild cases to fatalities. Early cases in the U.S. were mild, but there has been at least one U.S. death from swine flu. And it's impossible to know whether the virus will change, either becoming more or less dangerous. Scientists are watching closely to see which way the new swine flu virus is heading -- but health experts warn that flu viruses are notoriously hard to predict, as far as how and when they'll change.

Why has the swine flu infection been more severe in Mexico than in other countries?

That's not clear yet. Researchers around the world are investigating the differences between the cases in Mexico and those elsewhere.

Have there been previous swine flu oubtreaks?

Yes. There was a swine flu outbreak at Fort Dix, N.J., in 1976 among military recruits. It lasted about a month and then went away as mysteriously as it appeared. As many as 240 people were infected; one died.

The swine flu that spread at Fort Dix was the H1N1 strain. That's the same flu strain that caused the disastrous flu pandemic of 1918-1919, resulting in tens of millions of deaths.

Concern that a new H1N1 pandemic might return in winter 1976 led to a crash program to create a vaccine and vaccinate all Americans against swine flu. That vaccine program ran into all kinds of problems -- not the least of which was public perception that the vaccine caused excessive rates of dangerous reactions. After more than 40 million people were vaccinated, the effort was abandoned.

As it turned out, there was no swine flu epidemic.

I was vaccinated against the 1976 swine flu virus. Am I still protected?

Probably not. The new swine flu virus is different from the 1976 virus. And it's not clear whether a vaccine given more than 30 years ago would still be effective.

How many people have swine flu?

That's a hard question to answer, because the figure is changing so quickly. If you want to keep track of U.S. cases that have been confirmed by lab tests and reported to the CDC, check the CDC's web site. If you're looking for cases in other countries, visit the World Health Organization's web site. And when you hear about large numbers of people who are ill, remember that lab tests may not yet have been done to confirm that they have swine flu. And there may be a little lag time before confirmed cases make it into the official tally.

How serious is the public health threat of a swine flu epidemic?

The U.S. government has declared swine flu to be a public health emergency.

It remains to be seen how severe swine flu will be in the U.S. and elsewhere, but countries worldwide are monitoring the situation closely and preparing for the possibility of a pandemic.

The World Health Organization has not declared swine flu to be a pandemic. The WHO wants to learn more about the virus first and see how severe it is and how deeply it takes root.

But it takes more than a new virus spreading among humans to make a pandemic. The virus has to be able to spread efficiently from one person to another, and transmission has to be sustained over time. In addition, the virus has to spread geographically.