Bourbon virus is a recently discovered RNA virus in the genus Thogotovirus that has been associated with a fatal febrile illness. It was first recognized in a patient in Bourbon County, Kansas, in 2014. Since then, there have been a limited number of cases identified in the Midwest and southern United States. It is unknown whether the virus is present in other areas of the United States.

Thogotoviruses are thought to be transmitted by tick or other insect bites. The index patient with Bourbon virus had numerous tick bites days prior to developing his illness. Studies of ticks in eastern Kansas have suggested that Amblyomma americanum is the primary vector for Bourbon virus.

Because so few cases of Bourbon virus infection have been identified, the understanding of the clinical manifestations of infection will likely continue to evolve with further study. Per the National Center for Emerging and Zoonotic Infectious Diseases (NCEZID), symptoms associated with Bourbon virus infection include fever, fatigue, an exanthematous rash early in the disease course, headache and myalgia, and nausea and vomiting. Leukopenia and thrombocytopenia are also reported. Other laboratory findings include transaminitis, hypokalemia, and hyponatremia. Acute kidney injury and lactic acidosis may occur as the disease progresses.

The first documented infection developed in a previously healthy adult male who had known tick bites several days prior to the onset of nausea, weakness, and diarrhea. Fever, chills, headache, myalgias, arthralgias, and anorexia followed the next day, and by the fourth day, the patient became obtunded. Fever was persistent through at least the ninth day of illness, and the patient developed heart failure, respiratory failure, metabolic acidosis, acute kidney injury, and eventual cardiac arrest resulting in death. There are milder cases of Bourbon virus infection, and not all patients diagnosed with the infection have died.