Everything You Want to Know About the Measles

Measles was eliminated by vaccines years ago but is making a comeback.

— -- intro: The measles have made a comeback with 84 cases in the latest outbreak, not to mention 644 cases last year alone. Given that the infectious disease was eliminated more than a decade ago by vaccines, it's not surprising that its resurgence has some people scratching their heads.

Here's what you need to know:

Every person who gets it can spread it to an average of 18 other people.

About one or two in every 1,000 people who get it will die, according to the CDC. The disease was so widespread that hundreds of thousands of children died before a vaccine was introduced, Schaffner said.

quicklist: 2 category: title: How is it spread? url: text: The measles virus is airborne, meaning it can spread through the air and can remain airborne for a few hours. You can catch if from an infected person even after that person has left the room. According to the CDC, a sick person will spread the measles to 90 percent of the people close to them that are not immune.

The virus can also survive on surfaces for up to two hours, according to the CDC.

quicklist: 3 category: title: Why is it making a comeback? url: text: A measles vaccine was first licensed in 1963, and then lumped into the MMR vaccine in 1971, according to a timeline by the College of Physicians of Philadelphia. The vaccine is 95 percent effective and measles is considered a vaccine-preventable disease.

Cases steadily declined, reaching an all time low of 37 cases in 2004, according to CDC data. But thanks to "clusters" of unvaccinated people in the United States, coupled with increased international travel, cases are back up.

The CDC reported 644 measles cases in 2014 alone as part of about 20 separate outbreaks.