Why measles found new life in U.S.

There could be more cases of measles this year in the United States than we've seen in more than a decade. The Centers for Disease Control and Prevention reports it's already seen 98 cases in 2011 -- double the average number for an entire year.

Why is this happening?

CBS News Medical Correspondent Dr. Jennifer Ashton said it's often because people aren't vaccinated.

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She explained, "Before the measles vaccine, this was an infectious disease that was pretty significant in this country. Several million people got sick every year, (it) caused about 500 deaths in the U.S. per year. In 2000, the CDC reported we had really had a victory over measles because of the vaccine, and it was pretty much 99 percent eradicated. When we see cases today in this country, they are almost entirely brought in from other parts of the world, and the people who get sick here are those who are largely not vaccinated."

Ashton said the CDC reports 98 cases in 23 states. She noted the federal organization has not been pointing out which states are involved. No deaths have been reported.

The illness, Ashton said, is highly contagious. Among those exposed to Measles, 90 percent will get sick (if not vaccinated).

"It's transmitted via respiratory particles," she said. "People sneeze and cough, those particles become aerosolized or airborne. It can also live on dry surfaces for two hours. So it is highly, highly contagious."

She continued, "In about one-of-three people who get sick with measles, they will develop complications that can potentially be not only very serious but life-threatening. We're talking about pneumonia, ear infections that can rarely even cause deafness, or something like diarrhea. Again, the very young and adults over the age of 20, (are) most susceptible to those complications."

Symptoms of Measles:

• Develop about one-to-two weeks after exposure.
• Start with a fever that can be very, very high. About 104 degrees.
• Cough and runny nose
• Watery eyes
• Classic white spots with a blue center dot that occur in the mouth
• Classic measles rash starts in the face, head and proceeds down the lower body. Typically three-to-five days after the symptoms begin.

Ashton said there is currently no treatment for measles.

"It really just runs its course," she said. "And we treat the complications, if they occur."

Parents, Ashton said, should talk to their pediatrician about vaccines.

"There's two different types of vaccines," she said. "One of them is against the chicken pox virus, as well. They normally are given at about 12 to 15 months, which means that newborns and infants are very susceptible if someone has measles. The second dose of the vaccine is given at four to six years."