Syphilis continues to make a dismaying comeback in the United States.

Between 2012 and 2016, the rate of primary and secondary syphilis among women increased 111 percent. Over the same period, the rate of congenital syphilis increased by 87 percent.

The sexually transmitted disease is caused by infection with the bacterium Treponema pallidum. The bacterium also can be passed from mother to child during pregnancy or birth.

Up to 40 percent of infants with syphilis are stillborn. The rest appear normal at birth; if left untreated, however, they may develop a number of serious symptoms, from bone pain to deafness and blindness.

Infected babies are treated with penicillin. Infants who picked up the bacterium while passing through the birth canal generally fare better than those infected during pregnancy.