The Epidemiology of Weil's Disease: (Section of Epidemiology and State Medicine)

Adolf Weil defined the disease as a clinical entity in 1886, and Leptospira ictero-hæmorrhagiæ was found to be the causative organism in 1915 by Inada et al. in Japan, and confirmed by Hübener and Reiter in Germany. The infection has been found in most countries, and recently there has been a great increase in the number of instances reported.In most parts of the world rats and other small rodents harbour the organism and excrete it in the urine. This is almost always the direct or indirect source of infection of man, but natural infection of dogs and foxes takes place, and is at least a potential danger to human beings. Infection is usually related to occupation in coal-mines, field work of all sorts, sewers, fish-cleaning, and to bathing in fresh water.The organism quickly dies in an acid medium, in strong sunlight and in salt water. These facts accord with the presence of the disease in certain situations.The route of infection of man is usually by contact of the abraded or sodden skin with infected mud or water, but it may be by inhalation of water and by bites of rats, dogs, and ferrets.Men are much more exposed to infection than women, but in fish-cleaners the incidence is equal in the sexes. Children are sometimes infected by bathing and in houses.The incubation time may be four to nineteen days, and is usually seven to thirteen days.By serological methods many unjaundiced and subclinical infections can be detected among people who are often at risk, and these correct the rather high fatality rates which are derived from jaundiced cases only.During the last three and a half years 142 authenticated instances of the disease in an obvious clinical form have been reported in the British Isles. Twenty-one occupations or circumstances were involved, and the case fatality rate was 15 per cent.