FRESNO, Calif. (AP) – Fresno County health officials say the region’s syphilis rates have spiked, leading them to ask for help from state and federal agencies.

The Fresno Bee reports that the sexually transmitted disease was nearly nonexistent in Fresno County six years ago. Medical workers say its return might be linked to drug use and prostitution.

State officials say Fresno County’s syphilis rates were higher than every other county in California in 2015.

Officials from the federal Centers for Disease Control and Prevention and the state Department of Public Health-Sexually Transmitted Disease Control Branch are working with the county to look for solutions to the health crisis.

Syphilis can cause serious rashes and potentially significant nervous system issues. Congenital syphilis can cause death in newborns and problems for infants, including blindness.