Background: Murine (also known as flea-borne) typhus is uncommon in the U.S., but it is considered endemic in certain parts of Texas, especially the southernmost region. It is caused by Rickettsia typhi, which is transmitted to humans by rat and cat fleas. Murine typhus is often a mild illness with nonspecific clinical findings, though delayed treatment may result in severe disease and increased risk of complications. Diagnostic tests have low sensitivity in early disease. Therefore, correctly diagnosing patients with murine typhus is challenging unless clinical suspicion is high. In endemic regions, physicians are aware of the disease and diagnose it readily. However, in areas that have not historically been affected, physicians may be less familiar with the presentation of this rickettsial infection, impacting their ability to diagnose and treat it effectively.
Methods: Probable and confirmed murine typhus cases reported in Texas were collected for 1944-2017. Cases were mapped by county for each of the last 5 years. Cases reported over the last 5 years were also geocoded by residence for spatial cluster analysis by year.
Results: There has been an overall rise in the number of murine typhus cases reported per year over the last 13 years (figure 1). The distribution of reported cases throughout Texas has changed over the last 5 years. There continues to be a high number of reported cases in South Texas and Central Texas, while reported cases are increasing in the Harris County/Houston area, Tarrant County/Ft. Worth area, and Dallas County/Dallas area. Spatial cluster (hot spot) analysis of typhus cases in Texas over the last 5 years shows areas of increased risk of murine typhus in South Texas that have persisted over time, while other areas of increased risk have appeared more recently in North Texas and Central Texas (figures 2 and 3).
Conclusion: Murine typhus can be a difficult diagnosis to make based on clinical presentation, and physician awareness of its epidemiology is important. The gradual increase in case counts and the changing distribution of cases within Texas may put patients at risk of missed diagnoses. Recognizing the changing epidemiology of typhus in Texas may help inform public health education and control efforts.
B. Mayes, None