Ecologic Investigative Strategies to Determine Human Plague Exposure Sites, United States, 1991–2018

Plague is a rare but potentially life-threatening fleaborne zoonotic disease caused by Yersinia pestis. Public health agencies in the United States use multiple concurrent epidemiologic and ecologic strategies to determine Y. pestis exposure sites. We reviewed 196 plague case files from 1991-2018 to describe effort and yield of implemented strategies. All files included an epidemiologic component, and 71% were followed up with environmental investigations. Environmental samples were collected for laboratory testing in 88% of investigations. The percentages of investigations yielding laboratory evidence of local transmission varied from 28% for testing live-trapped rodents to 50% for pet serology. We suggest that collection and laboratory testing of samples should be prioritized when epidemiologic investigations implicate potential exposure in an unusual setting, in areas where many people could be at risk of exposure to Y. pestis, or in situations where prevention activities extend beyond educational outreach and incur greater costs.