Typhus fevers

Nature 
Typhus is an infection caused by infective organisms that are usually transmitted to humans by the bites of lice, fleas, mites or ticks. It occurs in several forms.
Background 
The causative organisms of all forms of typhus fever belong the the genus [Rickettsia]. These are organisms intermediate between bacteria and viruses in their properties and measure 0.5 micron or less in diameter.
Aggravates 
Type 
(E) Emanations of other problems