The West Texas measles outbreak continues to grow, now possibly spreading into the central part of the state and neighboring New Mexico, health officials said Friday.

Texas health officials say the number of people with measles has increased to 146 in rural West Texas outbreak that led this week to the death of a school-aged child who was not vaccinated

Measles is one of the most contagious viruses known to humans, experts say. Measles has been spreading across the U.S. for the last several weeks, sickening people in at least nine states amid a growing outbreak in western Texas.