(CNN) -- Back in 2000 measles was eliminated from the United States, according to the Centers for Disease Control and Prevention. But now a new CDC study tells us there were 17 outbreaks and 222 cases of the highly infectious disease reported in 2011.
An outbreak is defined as three or more cases linked by time or location. The average age of those infected was 14 and most were infected while traveling abroad. Seventy patients were hospitalized, but there were no deaths reported.
"Last year many U.S. travelers brought back more than they bargained for," said Dr. Ann Schuchat, director, CDC's Office of Infectious Diseases, National Center for Immunization and Respiratory Disease. "This is the most reported number of cases of the measles in 15 years."
Measles was wiped out in the U.S. for more than a decade, thanks in large part to the MMR (measles, mumps, rubella) vaccine. Cases here are sporadic and although the numbers reported seem relatively small, the CDC says vaccination is still key to maintaining elimination in the U.S.
"It's really important for families to know that measles are still a threat," Schuchat said. "In some places it's easy to exempt from a vaccine. We believe that for many parents a reason to decline a vaccine is they don't think the disease exist, they believe it's gone ... No one wants their child to die from measles in 2012."
Schuchat says although many parents opt out of vaccinations for philosophical, religious or personal beliefs, the vaccine has been studied extensively and is safe and effective.
The measles vaccine is delivered in two doses for children. The first comes between 12 and 15 months and the second between the ages of 4 and 6.
Two doses are also recommended for college students, health care professionals and international travelers who've never been vaccinated. Adults who have no recognizable immunity should get one dose. People born before 1957 don't need to be vaccinated. It's widely believed that they either had measles - or were exposed to it.
The CDC recommends anyone older than 6 months who's traveling internationally should get vaccinated.
The agency says this small rise in cases underscores the ongoing risk to those who have not been vaccinated. The disease still exists in many parts of the world - infecting 20 million and killing nearly 200,000 each year and putting Americans at risk of contracting the disease when traveling outside the country, or from those visiting the U.S. while infected with the virus. Ninety percent of last year's cases were exposed outside the country, the report found. And nearly 90% of those that got the disease last year were not vaccinated or their vaccination status was not known.
Measles is a respiratory disease caused by the measles virus. Symptoms included a high fever of 101 degrees or more, body rash that lasts for 3 or more days, runny nose and cough. The CDC says for every 1,000 children who get the disease one to two of them die. Between 2001 and 2008 there have only been two measles deaths confirmed by the CDC - a 13-year-old boy with and underlying condition, and a 75-year-old international traveler.
This year there have only been 27 cases reported so far. But Schuchat says that's no reason to let your guard down.
"What would happen if people didn't get vaccinated? We would have thousands and thousands of cases." With summer coming and people heading overseas for events like the summer Olympics she has this message: "For those of you traveling abroad, bring back memories and not measles."
And you don't have to travel to obscure places to be exposed. Last year there were more than 37,000 cases of measles in Europe alone, including 27 cases of encephalitis -- a serious infection that can lead to brain damage and possible deaths. Ninety percent of cases reported to in the WHO European region were found in just five countries: France, Italy, Romania, Spain and Germany.
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