High fever, aching eyes, hacking cough and after a week, every square inch of your body covered by red dots.

It's measles and the U.S. Centers for Disease Control and Prevention warns it's back, spreading and some doctors don't even recognize it.

"Most [medical] residents who are training have never seen measles," Dr. Mark Sawyer told ABC News.

There have been 129 measles cases this year, 58 of which were in California, compared to only four cases last year, according to the CDC. This is the biggest number of cases of measles since 1996, the agency noted.

The disease is so contagious that Sawyer has prepared "negative pressure" rooms in an emergency room at Rady Children's Hospital San Diego to isolate incoming measles cases.

Many infections are introduced by unvaccinated travelers bringing measles back home after trips to the Philippines, where there is an outbreak. An increasing number of parents who won't vaccinate their children or choose to delay vaccines past the recommended ages are also to blame, experts say.

(ABC News)

"We're up to four and a half percent of our children at kindergarten age who have not had all their vaccines," Sawyer said.

Hilary Chambers, with a baby exposed to measles, has something to say to parents who refuse to vaccinate.

"That's not fair to everybody else, you know, that's not fair," she said. "It's like you're relying on everybody else to do it for you."

For many pediatricians, it's a hot-button issue because it is a parent's right to vaccinate their child or not.

"Would you send your teen out to drive a car without wearing a seat belt?" asked Dr. Stuart Cohen, a San Diego pediatrician. " Would you go out on a boating trip with your family and decide who wants to wear life jackets and who doesn't?"