An outbreak of flea-borne typhus in Los Angeles County resulted in 57 cases as of Monday, CNN reports. On Friday, Pasadena County said it was experiencing “epidemic levels of typhus fever,” with 20 confirmed cases this year, compared to the one to five cases the county expects annually. The Department of Public Health announced Thursday it was investigating an outbreak in the downtown Los Angeles area, where nine cases were found between July and September. Six of those cases reportedly affected people experiencing homelessness. “We encourage pet owners to practice safe flea control and encourage all cities in the county to ensure maintenance of their trash clean-up and rodent control activities,” L.A. County Health Officer Dr. Muntu Davis said in a statement. The CDC said an uptick of diseases transmitted through “blood-feeding ticks, mosquitoes, and fleas” has been a “growing public health problem” nationwide.