Rickettsia are rod- or sphere-shaped microorganisms known as atypical bacteria because, although they are bacteria, they have virus-like qualities. They cause diseases, characterized by rashes and high fevers, that usually are contracted through insect bites, such as typhus and Rocky Mountain spotted fever. The exception is the microorganism that causes Q fever, which is inhaled as infected dust.

Rickettsia were first discovered by Howard Taylor Ricketts (1871-1910), an American pathologist, while studying Rocky Mountain spotted fever. Ricketts noticed that Rocky Mountain spotted fever resembles typhus, and he traveled to Mexico City to study that disease. He showed that typhus is transmitted by the body louse, but he also contracted typhus while in Mexico City and died there in 1910.

One of the difficulties confronting scientists studying rickettsial diseases was their inability to differentiate among the various microorganisms causing these diseases. American bacteriologist Ida Albertina Bengston (1881-1952) developed a diagnostic...