Now Los Angeles County Department of Public Health officials have issued a warning about another outbreak of typhus in the Pico-Union area. “In Los Angeles County, infected fleas are commonly found on rats, free-roaming cats, and opossums.” Flea-borne typhus outbreak in Pico-Union prompts warning from LA County health officials Los Angeles County health officials Wednesday reported a localized outbreak of flea-borne typhus in the Pico-Union neighborhood, where five people have become ill this year. “As flea-borne typhus cases continue to increase across Los Angeles County, preventing exposure to infected fleas is more important than ever,” said Muntu Davis, MD, MPH, Los Angeles County Health Officer. A review of the data suggests that Los Angeles is the rattiest city in the United States.