In the last three weeks, 48 cases of measles have been identified, sending 13 patients to the hospital, according to the Texas Department of State Health Services.

The ongoing measles outbreak in West Texas has doubled in size to 48 cases. It's the state's worst in nearly 30 years.

Measles is marked by high fevers and a telltale rash. People can spread the infection from four days before the rash develops to four days afterward. In addition to the miserable illness, measles can cause complications, particularly in children younger than 5, pregnant people, adults over the age of 20, and people with compromised immune systems.