Trench fever is caused by Bartonella quintana, which is transmitted by the human body louse (Pediculus humanus). This disease was first described during World War I. Although reported worldwide, it has reemerged in urban settings in Europe and the United States. For example, an outbreak of trench fever occurred among undomiciled individuals (people experiencing homelessness) in Colorado in 2020.

Trench fever may be prevalent in certain populations; researchers in Marseilles were able to culture B quintana from the blood of 14% of undomiciled patients presenting to their university hospital emergency department. Moreover, researchers in Tokyo found that 34.5% of undomiciled patients presenting to Saiseikai Central Hospital tested positive for immunoglobulin G (IgG) against B quintana.

Common symptoms and signs include headaches, retro-orbital pain, conjunctival injection, anterior tibial pain, myalgias, arthralgias, hepatosplenomegaly, truncal rash (80%-90% of patients), and fever, which cycles approximately every 5 days.

This disease is usually mild and self-limited; however, culture-negative endocarditis may develop, especially in those who are living with HIV, abuse alcohol, and/or are undomiciled.

Individuals may harbor the organism at a low level for many years, acting as a reservoir for new infections. Dental pulp stem cells may serve as sanctuaries for B quintana.

Individuals living in crowded, unhygienic conditions (eg, prisons, refugee camps, shelters) are at the highest risk for trench fever. Epidemic typhus occurs in the same at-risk populations and is carried by the same vector; cases of outbreaks of both diseases occurring simultaneously have been reported.

Individuals with HIV infection develop a more chronic presentation with weight loss and progressively higher fevers. Although uncommon, B quintana infection in these patients can also manifest as bacillary angiomatosis.