Now, to the measles outbreak, escalating around the country, shaping to be the worst in almost 20 years. According to the CDC, so far, cases of measles spiking in 13 states. ABC's medical editor, Dr.... See More
Now, to the measles outbreak, escalating around the country, shaping to be the worst in almost 20 years. According to the CDC, so far, cases of measles spiking in 13 states. ABC's medical editor, Dr. Richard Besser is here to report on why this is happening and what parents can do. Reporter: This is really concerning. So far, there's 129 cases of measles around the country. On track, the most since 1996. 58 of the cases in California. Last year, at this time, they only had four cases. The CDC is concerned. Measles is probably the most contagious disease we know of. And a lot of doctors have never even seen a case. So, some of the transmissions taking place in doctor's office. Here's what you look for. You're going to see a high fever. Red eyes. A hacking cough. And then, you have a rash that starts with dots around the forehand and then, throughout the entire body. Why is this happening now? Is it concerns about vaccinations? There's two things going on. We have outbreaks of measles around the globe. And you're seeing pockets where parents are saying, I either don't want to vaccinate or I'm going to delay vaccination. You have some schools in California where 20% of the kindergarten kids haven't been vaccinated. And that's really concerning. T alarming because it not only affects that child, but those around them who have compromising systems. Very young children. You can't be vaccinated. And young children at risk. And people like yourself, who are going under treatment for cancer, they're at risk for these diseases. That's concerning. Part of the issue here is that people got misinformation about connections of vaccines and autism. And a lot of people are taking advice from celebrities. It's very dangerous. Vaccinate your children. An airplane ride away, measles can be here. Vaccinate to protect your own child and everybody else around you. Important information. Thank you, as always.
This transcript has been automatically generated and may not be 100% accurate.