The beginning of an era of functional genomics in Rickettsiology is steeped in history

Human diseases caused by bacteria in the genus Rickettsia , commonly referred to as typhus or spotted fevers, are among the oldest and most severe scourges of humankind. All of the diseases’ agents utilize blood-sucking arthropods as vectors, which influences disease epidemiology. Epidemic typhus continues to cause outbreaks today in situations of war and unrest (1), and the incidence of Rocky Mountain spotted fever is growing in the Americas (2). Despite an urgent need, broadly protective vaccines are unavailable, although previously used vaccines proved this an achievable goal (3). It has long been known that recovered patients mount protective immune responses, producing antibodies that have been used for diagnosis of rickettsioses through the so-called Weil−Felix reaction since the early 1900s (4). However, until the research by Kim et al. (5), the identity of the genes encoding the molecular machinery responsible for producing the cognate antigen in all species of rickettsiae was unknown. The history of the Western world reflects the power of rickettsial disease agents. Epidemic typhus, which may kill over 30% of infected people, has shaped history profoundly at least since medieval times (6), when hapless inhabitants of cities beleaguered by enemy armies were forced to live in crowded quarters and under unsanitary conditions. This created favorable conditions for human body lice, the vectors for the causative agent, Rickettsia prowazekii (7). Soldiers … [↵][1]1Email: munde001{at}umn.edu. [1]: #xref-corresp-1-1