According to the society, the last US measles death was in 2015. A measles infection can have particularly devastating complications for pregnant women and young children, including pneumonia, neurological impairment, hearing loss and death.

At least 124 cases of measles have been identified in Texas since late January, mostly among children and teenagers who are either unvaccinated or whose vaccination status is unknown, officials say.

As a measles outbreak sweeps through Texas, anti-vaccine groups are pushing a familiar and false theory: The virus is being caused by the vaccine itself.