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In a follow-up on a pneumonic plague case reported in Wyoming last September 2021, the Centers for Disease Control and Prevention (CDC) published a Notes from the field in Friday’s Morbidity and Mortality Weekly Report (MMWR) that details the investigation.

The individual was admitted to a Wyoming hospital following a 48-hour history of worsening cough, dyspnea, and acute onset of hemoptysis.


The patient reported no recent travel history or ill contacts but noted interacting with two pet cats that were ill.

Health care providers initially suspected COVID-19 because of compatible symptoms, no history of COVID-19 vaccination, and increased SARS-CoV-2 (the virus that causes COVID-19) community transmission in Wyoming during this period.

The authors write: Approximately 48 hours after symptom onset, the patient received a negative SARS-CoV-2 antigen test result at a provider’s office. The patient was hospitalized later that day for worsening symptoms and received two negative SARS-CoV-2 laboratory-based nucleic acid amplification test results. Lung imaging was consistent with community-acquired pneumonia. Respiratory specimens tested negative for common viral pathogens on a respiratory panel. Within 48 hours of admission, the patient required mechanical ventilation and developed sepsis. The patient was treated for pneumonia and sepsis with azithromycin, piperacillin-tazobactam, and vancomycin. Seventy-two hours after the patient was admitted to the hospital, blood and sputum cultures did not indicate a causative pathogen. Because of the patient’s history of exposure to cats that were ill, an infectious diseases specialist recommended repeating a sputum culture with Gram stain and empiric treatment with ciprofloxacin. Gram-negative bacilli were detected, and the Wyoming Public Health Laboratory subsequently confirmed Yersinia pestis as the pathogen.

The Wyoming Department of Health  immediately conducted interviews to determine exposure source, identify close contacts requiring postexposure prophylaxis (PEP), and guide public health prevention measures. Interviews with veterinary clinic staff members and review of records revealed that one cat had died from an undiagnosed severe illness after onset of respiratory symptoms; serologic testing of specimens from the surviving cat for Y. pestis by CDC was negative. WDH interviews with local animal control and state wildlife officials revealed no known epizootic near the patient’s residence, which was in a rural area of Wyoming; however, both pet cats were known to spend time indoors and outdoors and were not treated with flea control products.

This is the second case of primary pneumonic plague and the seventh of any form of plague in Wyoming’s documented history. Nationwide, 18 cases of pneumonic plague were reported during 1942–2018.

Read more at MMWR