The number of measles cases exceeded 500 in Texas on Tuesday, according to the state’s health department, which made the update days after a second Texas child died after contracting the highly contagious illness that has been confirmed in at least 20 states.

A measles outbreak that has caused the deaths of two school-aged children has now surpassed more than 500 cases across Texas, according to health officials. The latest update from the Texas Department of State Health Services shows that 505 people have been infected with measles since the outbreak began in late January in the South Plains region.

More than two months in, the West Texas outbreak is believed to have spread to New Mexico, Oklahoma and Kansas, sickening nearly 570 people. The World Health Organization also reported cases related to Texas in Mexico.