Differential Diagnosis

The patient's symptoms and history suggest a severe respiratory infection, possibly caused by a bioterrorism agent. The differential diagnosis can be categorized as follows:

• Single most likely diagnosis
  • Bacillus anthracis: The patient's symptoms, including high-grade fever, cough, chest pain, and shortness of breath, are consistent with inhalational anthrax. The widened mediastinum on the chest radiograph is a characteristic finding in inhalational anthrax. The patient's exposure to an improvised explosive device in the Middle East, a region where anthrax has been used as a bioterrorism agent, increases the likelihood of this diagnosis.
• Other Likely diagnoses
  • Francisella tularensis: Tularemia can cause a severe respiratory infection, and the patient's symptoms, including fever, cough, and chest pain, are consistent with this diagnosis. However, the widened mediastinum on the chest radiograph is more characteristic of anthrax.
  • Influenza or other viral pneumonia: The patient's symptoms, including high-grade fever, cough, and shortness of breath, could be consistent with a severe viral pneumonia, such as influenza. However, the widened mediastinum on the chest radiograph is not typical of viral pneumonia.
• Do Not Miss diagnoses
  • SARS-CoV-2 or other severe viral respiratory infections: Although less likely, it is essential to consider other severe viral respiratory infections, such as SARS-CoV-2, in a patient with severe respiratory symptoms, especially given the patient's travel history and exposure to potentially infected individuals.
  • Pneumonic plague (Yersinia pestis): Pneumonic plague is a highly infectious and deadly disease that can cause severe respiratory symptoms, including fever, cough, and chest pain. Although less likely, it is crucial to consider this diagnosis, especially given the patient's exposure to an improvised explosive device in a region where plague has been reported.
• Rare diagnoses
  • Marburg virus: Marburg virus is a rare and highly infectious disease that can cause severe hemorrhagic fever, but it is less likely to cause a primary respiratory infection.
  • Rickettsia prowazekii (epidemic typhus): Epidemic typhus is a rare disease that can cause fever, headache, and rash, but it is less likely to cause a severe respiratory infection.
  • Vaccinia virus: Vaccinia virus is a rare cause of infection, typically associated with vaccination or laboratory exposure, and is unlikely to cause a severe respiratory infection in this patient.