Last fall, you’d have been forgiven for thinking that measles was a disease of the past, but one infected child at Disneyland was enough to change all that. Due to an outbreak over the holidays at that theme park in California, 102 cases of measles were reported in 14 states in January alone. By contrast, the median number of cases reported in the United States between 2001 and 2010 was 60 per year, according to the Centers for Disease Control and Prevention (CDC).

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Because this viral disease is America’s newest outbreak, you might want a refresher course on what it entails.

Here’s what you should know about measles:

1. It’s more than just a rash

“Measles is potentially very serious,” says Mayra Rosado, a pediatrician at HealthCare Partners in Torrance, Calif. “It can lead to pneumonia, swelling of the brain and even death.” Rosado says, however, that death from measles is rare. Complications are more common in patients under 5 and over 20, but measles primarily affects children, she says.

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So what happens when your kid contracts the measles? Like all viral infections, there is an incubation period. “Symptoms begin anywhere from seven to 14 days after one is infected,” Rosado says.

Those symptoms may resemble a chest infection or pinkeye. Patients typically have a combination of fever, cough, runny nose, sore throat and inflamed eyes. “About three to five days after these symptoms begin, a rash develops on the face and hairline and then spreads downward,” Rosado says. It consists of red spots and bumps, and since the bumps come in clusters, the skin is blotchy and red.

At the same time the rash is spreading, the fever typically spikes and may reach nearly 106 degrees. The rash then starts to fade, again from the top of the head all the way to the bottom of the feet.

2. It’s pricey to treat

“There is no prescription medication to treat measles,” Rosado says. As with many viral illnesses, the treatment for measles focuses on managing complications and dealing with specific symptoms rather than targeting the virus itself. Fever, cough, itching, and other symptoms are all treated separately.

People infected with measles are contagious for four days before and after the initial appearance of the rash, for a total of eight days. During that time, the virus is so contagious that 90 percent of unvaccinated people exposed to it will catch it, and even some people who have been vaccinated can fall ill. For this reason, measles patients are often isolated, and the health care workers who treat them use extra precautions— a practice that can get expensive.

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One case study published in 2012 in the journal Vaccine focused on a refugee who had come to the U.S. infected with measles. That study found that this single case of measles cost a total of $25,000.

A larger study looked at a measles outbreak in San Diego in 2008, where 12 children, all of whom were unvaccinated, contracted measles. The study, published in the journal Pediatrics, found that each case cost $10,376 to treat, including insurance payments. The out-of-pocket costs to each family averaged $775.

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3. There’s no scientific evidence that the measles vaccine is unsafe

You may have heard a lot of discussion over the safety of vaccines. Many parents in recent years have decided against vaccinating their children due to a belief that vaccines are unsafe and may cause harm. Specifically, the measles-mumps-rubella (MMR) vaccine has been accused of causing autism spectrum disorders in children after exposure.

This misconception dates back to a 1998 study of 12 developmentally disabled children in London, published in the medical journal The Lancet by lead author Andrew Wakefield. In the study, the onset of symptoms was reported to coincide with the MMR vaccine the children received. However, it was later discovered that the paper contained fraudulent data and that Wakefield had planned to use it to sue vaccine makers. The study was later discredited by three separate scientific boards and retracted by The Lancet.

Doctors say vaccines are an important part of maintaining public health. “I cannot emphasize enough the importance of immunizing your children,” Rosado says. “Because of vaccines, we’ve been able to eliminate life-threatening diseases like smallpox in the U.S.” Other diseases, such as polio and diphtheria, Rosado adds, have become extremely rare in the U.S. because of vaccines.