The number of measles cases in the United States has reached 288, the highest annual rate in 20 years, the US Centers for Disease Control and Prevention (CDC) reported Thursday.

The health agency blames foreign travel, mainly to the Philippines, and urges people who haven't done so already to get vaccinated. The virus can spread when it reaches US communities in which group of people are unvaccinated.

Measles was eradicated from the United States in 2000, BBC News reported, meaning that for more than 12 months there was no longer any continuous measles transmission. Dr. Anne Schuchat, director of CDC's National Centre for Immunizations and Respiratory Diseases, describes this dramatic spike - which began October 2013 - as a "wake-up call."

"The current increase in measles cases is being driven by unvaccinated people, primarily US residents, who got measles in other countries, brought the virus back to the United States and spread to others in communities where many people are not vaccinated," she said in a CDC press release.

Of the 288 cases, 280 were thought to have been imported from at least 18 countries, and one in seven instances has led to hospitalization.

Most cases could have been prevented with a simple injection, as 90 percent of all US measles cases occurred in people who were not vaccinated or whose vaccination status was unknown.

Measles is a highly contagious illness, with symptoms like fever and rash along with cough, runny nose, or pink eye.

It is deadliest to pregnant women and children. The CDC recommends infants between 12 and 15 months old get vaccinated, however, if travelling internationally, any baby as young as 6 months old should get a shot.

Measles is still common in many parts of the world, including countries in Europe, Asia, the Pacific, and Africa. Worldwide, an estimated 20 million people get measles and 122,000 die from the disease each year.