Fevers, fatigue, and brain fog

Andy McDonald, an Oregon resident with a history of Crohn's disease, initially presented with recurring high fevers and "brain fog," symptoms that quickly intensified. "I'd be sleeping and a fever would come on, and when I woke up, the sheets were wet — like someone dumped water on them," he said.

As his condition worsened, McDonald was hospitalized with suspected sepsis and treated with broad-spectrum antibiotics. Though he briefly improved, his symptoms quickly returned, this time with rapid weight loss, persistent gastrointestinal issues, and respiratory complications.

Clinicians launched an extensive workup, consulting specialists and testing for a range of infectious and noninfectious causes but results repeatedly came back negative. "It looked infectious, but didn't act like anything we knew," one infectious disease physician said.

With his health continuing to decline, concern shifted to more serious possibilities, including cancer. "Everyone thought he had lung cancer," said a physician involved in McDonald's care. "We thought this patient was going to die."

 This shift in thinking prompted clinicians to pursue more targeted infectious disease testing.

Those tests ultimately confirmed pulmonary tularemia, a rare bacterial infection caused by Francisella tularensis. The disease can be transmitted through inhalation, contaminated water, or exposure to infected animals such as rodents — aligning closely with McDonald's recent exposures.

"I had never seen a case of tularemia before," the infectious disease specialist said. "And I haven't seen one since."

The diagnosis clarified why McDonald's condition had continued to worsen. Tularemia is intrinsically resistant to many broad-spectrum antibiotics, rendering the initial treatments ineffective.

Once clinicians shifted to a targeted antibiotic, his recovery was swift. His lungs cleared, the fluid resolved, and the brain fog lifted.

"You just appreciate not feeling sick anymore," McDonald said.