born Feb. 9, 1871, Findlay, Ohio, U.S.
died May 3, 1910, Mexico City, Mex.
U.S. pathologist.
He received his medical degree from Northwestern University. He discovered the bacterium (named rickettsia ) that causes Rocky Mountain spotted fever and epidemic typhus . He demonstrated in 1906 that the former could be transmitted by the bite of a certain tick and identified a bacterium in the blood of infected animals, in the ticks, and in their eggs. He found that epidemic typhus in Mexico was transmitted by a louse and found a related bacterium in the victim's blood and in the lice. He transmitted the disease to monkeys, which developed immunity. He died of typhus later that year.