It is the policy of the Division of Preventable Diseases of the Minnesota State Board of Health to determine if possible the source of infection in all sporadic cases of typhoid fever as well as in outbreaks of considerable magnitude. The search for carriers as prosecuted by this division during the past three years has been so satisfactory that a review of the methods used, together with brief histories of the cases, is here presented.
On receipt of a report of a case or suspected case of typhoid fever, or on the finding of a positive Widal reaction in a specimen of blood sent to the laboratory, a blank, requesting certain epidemiologic data, is sent to the attending physician. This blank, when properly filled in, gives the following environmental data: residence and occupation; milk and water supply of patient during the three weeks prior to onset of disease; exposure to