Typhoid fever and typhus fever were only separated as distinct diseases by Gerhard, 1837. Huxham, however, had previously noted the marked difference between putrid malignant fever and slow nervous fever.
Until very recent times it was declared that typhus fever was among the most contagious diseases of man and innumerable instances were cited of frequent contagion of those attending or visiting typhus patients. In 1909, Nicolle, in North Africa, demonstrated that the disease was transmitted by lice and the recent experiences in the Balkan war and in the Servian epidemic of 1915 show that in the absence of such vermin the disease does not appear to be contagious.
Geographical Distribution.—The disease has largely been eradicated from European and other countries where hygienic measures leading to the destruction of vermin have existed.
During the recent war the disease became one of importance, owing to the difficulty of preventing the spread of body lice to the soldiers.
In the tropics the disease, when present, is usually found in regions of high altitude. In Mexico tabardillo, as typhus is there designated, is a disease of the elevated regions. This is also true of India.
Sporadic cases of typhus, known as Brill’s disease, have appeared from time to time in New York.
During the great war typhus first appeared in Servia, thence extending to Austria, Germany and Russia. Its nonappearance on the Western battle line must be attributed to the active measures of the Germans in attacking the lice problem. It is now widespread in Russia and Poland.
Etiology and Epidemiology
Etiology.—Recent work by Anderson and Ricketts has shown that the blood of human cases is infective for monkeys. The virus does not seem to pass through a Berkefeld filter and the epidemiology points to the body louse as the sole transmitting agent. Nicolle reported the filterability of the virus. More recently he has considered this filterability as doubtful.