Health authorities warned of further spread. Most U.S. measles cases this year involved people 19 and under and those without a confirmed vaccination.

A measles outbreak in the southwestern United States has infected nearly 100 people in recent weeks. The deadly illness has sickened dozens of people in west Texas and New Mexico since late January. The Texas Department of State Health Services confirmed 90 cases of measles,

Texas reported 90 cases this week, while New Mexico reported nine. A majority of the cases have been in a Texas county where vaccination rates have lagged behind the rest of the state.

Measles is a highly contagious disease. Here’s what to know about how to protect yourself and what’s happening in Texas and New Mexico.

Mexico's Ministry of Health issued a travel warning advising citizens traveling to the United States to take precautions against measles.

Lea County, New Mexico, is now reporting an outbreak of measles, according to the New Mexico Department of Health (NMDOH). Lea County is near Gaines County, Texas, where measles cases continue to rise as part of the original outbreak.

In response to the ongoing measles outbreak in Texas, the Mexican government has issued a travel advisory cautioning its citizens against traveling to the Lone Star State.

Mexico has issued a warning to its citizens asking them not to travel to Texas and seven other states in the U.S. due to a measles outbreak.