Top 5 Takeaways

  1. Pneumonic Plague Misdiagnosed Amidst COVID-19: An adult admitted to a Wyoming hospital for respiratory symptoms initially suspected to be COVID-19 was later confirmed to have pneumonic plague.
  2. Initial COVID-19 Focus Delays Diagnosis: Despite negative tests for SARS-CoV-2, it took days before the correct diagnosis of pneumonic plague was made, highlighting the challenge of diagnosing rare diseases during a pandemic.
  3. Animal Contact Clue to Diagnosis: The patient’s contact with ill pet cats was a key factor leading to the correct diagnosis, emphasizing the importance of considering animal contact in patient histories.
  4. Rapid Public Health Response: Following the diagnosis, Wyoming Department of Health conducted interviews, identified close contacts for prophylaxis, and initiated community-wide education on plague prevention.
  5. Importance of Flea Control in Pets: This case underscores the significance of flea control for pets to prevent plague transmission, as pets can be a bridge between wild rodents and humans.

Original Article Author and Citation

Corresponding Author

Allison Siu,

Suggested Citation

Siu AW, Tillman C, Van Houten C, Busacker A, Harrist A. Notes from the Field: Diagnosis and Investigation of Pneumonic Plague During a Respiratory Disease Pandemic — Wyoming, 2021. MMWR Morb Mortal Wkly Rep 2022;71:806–807. DOI: 10.15585/mmwr.mm7124a5.


The case involves a Wyoming resident admitted to the hospital with symptoms initially indicative of COVID-19, such as cough, dyspnea, and hemoptysis, but later confirmed to be pneumonic plague. This case demonstrates the complexities of diagnosing rare diseases amidst a pandemic and the critical role of considering animal contacts in clinical assessments.


The diagnosis process was detailed, from initial COVID-19 suspicion due to symptom similarity and lack of vaccination, through various testing phases that eventually led to the identification of Yersinia pestis, the bacterium causing plague.


This incident highlights the challenge of distinguishing between common pandemic-related illnesses and rare diseases. It emphasizes the importance of rapid and accurate diagnosis, the role of animal contact history, and the need for timely public health interventions.


The effective response by health authorities to a rare case of pneumonic plague amidst the COVID-19 pandemic underlines the importance of vigilance, comprehensive patient history assessments, and the need for public education on disease prevention, especially in areas where such pathogens are endemic.

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