CDC staff received an email this week telling them to avoid using more than a dozen terms or words-- including "health equity," "race," "bias," and "disparity" -- in their annual performance evaluations;

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.

A school-age child has died of measles in West Texas, the first death from the disease in the U.S. since 2015 according to the CDC.