An investigation carried out by CDC has revealed that a San Diego measles outbreak was a direct result of parents refusing to get kids vaccinated, and this has also endangered those kids who are still too young to receive the vaccination.

Measles has been designated as the world's most highly contagious viral disease, and thanks to the high rates of vaccinations, the potentially killer illness had started to stop circulating across the US. But now, there are some worrying signs that the disease might just make a comeback.

The main reason for the looming danger is that there are still pockets of parents who tend to believe that the measles/mumps/rubella (MMR) vaccine is actually more dangerous than the disease itself. In England, the same belief had lead to a drop in the vaccination rates, and measles then came back with full-force.

Now, an in-depth study into the 2008 measles outbreak of San Diego has suggested that America could face the same fate.

The outbreak had begun in January of 2008, when a 7 year old boy's parents refused to get him vaccinated after they returned to the US from Switzerland. Even before the symptoms appeared, the boy had infected his 3 year old brother and 9 year old sister. Neither of them were vaccinated.

"Even with the very high vaccine coverage that we saw in San Diego, if you have a community of vaccine refusers you can get an outbreak", said Dr. Jane Seward CDC's senior investigator for the outbreak.