The number of measles cases and outbreaks spiked last year, with unvaccinated people making up the majority of those affected, according to a new report from the Centers for Disease Control and Prevention.

In 2011, there were 222 cases of measles in the United States. That's the highest number of cases reported here in 15 years, and more than triple the number of cases in 2009 and 2010.

About half of the 2011 cases occurred during outbreaks, which are defined as at least three cases that are linked to each other. Last year, there were 17 measles outbreaks, well above the average of four for the previous decade.

Among patients who were U.S. residents, 72 percent of cases developed in people who had not received the measles vaccination, or did not know if they had been vaccinated, despite being eligible for the vaccine. (Twenty-six cases occurred in people living outside the U.S.)

Fifty patients were children between 16 months and 19 years old who had not been vaccinated for philosophic or religious reasons or personal objections, the report says.

Since 2000, measles has been considered eliminated in the United States. The disease occurs here mostly when people become infected after traveling to other countries and transmit the disease to others upon their return. Indeed, 90 percent of the cases in 2011 had their origins in other countries, including 52 U.S. citizens who became ill after traveling abroad.

In 2011, more than 30,000 cases of measles were reported in European countries, with France, Italy, Romania, Spain and Germany having the majority of cases.

The presence of unvaccinated people who are susceptible to the virus also contributed to the high number of cases last year, said Dr. Anne Schuchat, director of the CDC's National Center for Immunization and Respiratory Disease.

"We don't have to have this much measles, because measles is preventable," Schuchat said.

Unvaccinated individuals "continue to place themselves and others in their communities at risk for measles and its complications," the report says.

The measles, mumps and rubella vaccine is recommended for all children ages 12 to 15 months, with a booster shot at age 4 to 6 years. Children as young as 6 months can recieve the vaccine if there are plans for the family to travel abroad. Adults should be vaccinated if they did not recieve the vaccine when they were younger.

Measles can be serious — one in three people who got measles last year had to be hospitalized. It is highly contagious, and causes fever, runny nose, cough and a rash all over the body, according to the CDC. For every 1,000 children who get the disease, one or two will die, the CDC says.

Parents may forego vaccinating their children because they don't realize these diseases are still around and can cause illness, Schuchat said. "For many parents, they really don't think there's a threat of disease, they think these disease are gone," Schuchat said. Unfortunately, measles is not gone, she said.

Schuchat noted the number of cases in a country can rise dramatically if people are not vaccinated. France went from having about 30 to 40 cases in 2005 to 2007, to 1,500 cases in 2009, to more than 15,000 in 2011.

There have been 27 cases of measles this year in the United States, and it is not clear whether we will have more cases than last year, Schuchat said.

Pass it on: There were more cases of measles in the United States last year than in any other year since 1996.

This story was provided by MyHealthNewsDaily, a sister site to LiveScience. Follow MyHealthNewsDaily staff writer Rachael Rettner on Twitter @RachaelRettner. Find us on Facebook.