U.S. and world leaders are working to stop the spread of a new type of swine flu that can easily be spread from person to person.

In the U.S., about 100 people have come down with swine flu. The majority of them have gotten better after receiving medicine. In 14 states, officials closed at least one school after students either got swine flu or were thought to have it. In Texas, officials closed the Fort Worth school system through May 8 as a precaution.

Swine flu has hit the country of Mexico hardest. There, several people have died and about 2,500 more are suspected of having the illness. Mexico has shut down most of its businesses and schools until at least May 6. Similar closures are not expected to happen in the U.S.

Swine flu is a serious illness, but officials say people should not panic.

"This is . . . a cause for concern," U.S. President Barack Obama said, "[b]ut it's not a cause for alarm."

U.S. and world health officials are particularly concerned because this swine flu is a new strain. However, flu outbreaks, in general, are common. There are simple things people can do to help prevent the spread of the disease, such as covering their mouths when they cough or sneeze and washing their hands.

Tracking Swine Flu

This new type of flu, officially called H1N1, is a disease that began in pigs. Originally, people got swine flu by being in very close contact with pigs. This new type of flu is easily spread from person to person.

People cannot get swine flu from eating well-cooked pork. The H1N1 virus is spread from person to person, usually through coughs and sneezes.

So far, the World Health Organization (WHO) says there are 257 cases of swine flu in 11 countries. Of these, 109 are U.S. cases.

The U.S. Centers for Disease Control and Prevention (CDC) says swine flu has been seen in 11 states: Arizona, California, Indiana, Kansas, Massachusetts, Michigan, Nevada, New York, Ohio, South Carolina, and Texas. New York State has the most cases (50) of swine flu in the U.S. The one U.S. death happened in Texas involving a visitor from Mexico.

Officials think the swine flu outbreak began in Mexico. Mexican health officials say eight people there have died from the disease.

Treating Swine Flu

Symptoms of swine flu resemble those of other types of flu. Symptoms can include fever, feeling tired, poor appetite, coughing, sneezing, sore throat, and headache.

Flu shots don't prevent people from getting swine flu. However, doctors can give sick people medicine to help them feel better.