A measles outbreak in Texas has grown to 90 cases, mostly among unvaccinated children, state health data published Friday shows.

Over the past month, the virus has spread in areas with low vaccination rates, and most of those affected are minors.

Some private schools have shut down because of a rapidly escalating measles outbreak in West Texas. Local health departments are overstretched, pausing other important work as they race to limit the spread of this highly contagious virus.