The ongoing Texas measles outbreak has rapidly grown to the largest the state has seen in decades, spreading through mostly unvaccinated residents and creeping across both county and state lines. On Friday morning,

A measles outbreak that began in northwest Texas last month has now sickened 90 people, the vast majority of whom were unvaccinated, according to state data released Friday -- and the figure is expected to rise further.

Only five of the infected individuals were vaccinated, with the rest either unvaccinated or having unknown vaccination status.