If you didn't vaccinate your kids, you too could find yourself partly responsible for the resurgence of a disease thought eliminated in 2000.

Measles—a highly contagious disease-causing virus—is making a comeback in the U.S., thanks to parents fears over vaccines. Fifteen children under 20, including four babies, have been hospitalized and 131 sickened by the red splotches since the beginning of this year in 15 states and the District of Columbia, according to the U.S. Centers for Disease Control.

The CDC had announced in 2000 that the disease was eliminated in the U.S. thanks to a vaccine that can completely control it. But fears of autism have led some parents to forego this treatment and at least 63 of the sickened children were unvaccinated.

Peditrician Pauline Filipek of the University of California, Irvine told ScientificAmerican.com this spring that parents who don't vaccinate their kids are putting the tykes at risk of long-forgotten diseases, like measles. What they're not doing: preventing autism.

"Many, if not most, of the younger siblings [of autistic children] never have any vaccinations," says Filipek, who believes that autism is not caused by vaccines. "And they are as autistic as the day is long."

Because the disease is highly contagious, it is the first to come back when vaccination falters. This is in part due to travel to other countries, such as Italy, Switzerland and the U.K., where similar outbreaks are occurring among children who have not been vaccinated. In previous years, such imported cases had petered out due to widespread vaccination but now the disease can spread.

So far, Illinois has the most cases, with 32 cases, followed by New York and Washington. In all of 2006, the latest year with full figures, there were only 55 cases total and an estimated 93 percent of U.S. children had been vaccinated. In fact, this is the most cases in such a short time span since 1996 and is due to "viral transmission after importation," according to the CDC.

It remains unclear whether vaccination levels overall are dropping or not, but at least 95 percent of children must be vaccinated to prevent measles from returning. The disease has become endemic to the U.K., for example, thanks to a vaccination rate that has fallen to 85 percent. Already one child has died in the U.K.

Prior to the vaccine's introduction in the 1960s, as many as 4 million people came down with measles each year and as many as 450 died as well as 4,000 who developed permanent disabilities when the measles inflamed their brains.

(Photo: John Heseltine/CORBIS)