In 2015 there have been over 114 confirmed cases of measles in the United States. The state that has been most affected by the disease is California, with close to 100 confirmed cases.

What this means is that the United States is currently going through a large-scale measles outbreak that began in Disneyland this past December. Since then, the disease has spread to multiple states and to Mexico and Canada. More cases are being confirmed as the weeks go on.

The Center for Disease Control, or CDC, is worried about a large outbreak that could affect the nation, since there are already over 100 cases in over a dozen different states.

The ongoing outbreak has led to thousands of people being exposed to the disease. On February 12, it was reported that a resident of San Francisco, who is infected with measles, traveled to and from work on the BART, the Bay Area Rapid Transit.

The resident was diagnosed with the disease and road the BART for three days after after being confirmed infected. BART officials say the resident rode the train for 35 minutes each way during rush hour, potentially infecting everyone in the vicinity.

Health officials said that the disease could have stayed in the air for two hours after the rider left because it is an airborne virus. Since the BART cars circulate throughout the Bay Area, tens of thousands of people could have been exposed.

The CDC reports that almost every case of measles in the United States can be tracked back to exposure in other countries. Measles was declared eliminated from the United States in 2000, but has reappeared when exposed travelers transmit it to unvaccinated Americans.

Measles is a highly contagious virus. According to the CDC, if a person has the disease, 90 percent of the people close to them will also become infected if they have not been vaccinated. The virus is in the mucus in the infected person’s nose and throat. When they cough or sneeze, the mucus will get into the air and infect surrounding people. It can also live for two hours on surfaces.

The early signs of measles include a mild fever, cough and runny nose. The person may have a sore throat and their eyes may be red. After a few days, white spots begin to appear inside the persons mouth followed by a rash starting on the face and moving down their body. The disease can lead to pneumonia, encephalitis and potentially death.

Southern Methodist University requires all students to provide documentation that proves they have been vaccinated for measles, mump and rubella. Students are not able to register for classes until they provide documentation that they have been immunized.

Doctors in Dallas are on high alert for any signs that the disease is in the Lone Star State. There are currently no cases in Texas, but two counties in North Texas have high rates of unvaccinated children. Both Denton County and Collin Country have thousands of unvaccinated residents.

The last outbreak of measles in Texas was in 2013, when a traveler brought the disease over from Indonesia. The traveler infected 27 people in the Newark, Texas area. The disease was spread through the congregation at the Eagle Mountain International Church, where many of the people who attended were not vaccinated.

The only way to prevent measles is to get the vaccination. Some parents are hesitant to get their children vaccinated because they falsely believe there is a connection between vaccinations and autism.

Medical experts say there is not a connection between vaccinations and autism and that parents’ fears are hurting their children more than protecting them. Now politicians are taking sides on whether vaccines should be required if it impacts public health.