YELLOW FEVER 1. Infective Agent.—Probably the spirochete (Leptospira icteroides) reported by Noguchi.
2. Source of Injection.—Typical and atypical cases of yellow fever, possibly only during the first three days of their illness.
3. Portal of Exit.—Blood abstracted by Stegomyia fasciata (Aedes calopus) (Fig. 78).
4. Route of Transmission.—So far as known only by the agency of one species of mosquito, Stegomyia jasciata, which has fed upon the blood of yellow fever patients. The unknown parasite undergoes an extrinsic incubation period in the mosquito of at least 12 days before the mosquito can transmit the virus.
5. Portal of Entrance.—Through the puncture wounds in the skin made by mosquitoes, to the subcutaneous tissues.
6. Incubation Period.—(Intrinsic) from three to six days.
7. Period of Communicability.—Probably only during the first three days of the illness.
8. Methods of Control. The Injected Individual.—(a) Di agnosis: Clinical observations only.
(b) Isolation: In a well screened room or ward which has been freed of mosquitoes.
(c) Immunization: None.
(d) Quarantine: Of contacts for six days.
(e) Concurrent Disinfection: None.
(/) Terminal Disinfection: Fumigate to get rid of mosquitoes.
General Measures.—(a) Eradication of mosquitoes by meas ures described under malaria. Since the habits of Stegomyia differ from those of anophelines, some difference in the water accumulations attacked must be noted. The Stegomyia is a species that lives closely in association with man, breeding largely in artificial accumulations of water close to dwellings, such as cisterns, barrels and cans (Fig. 79). It is diurnal in its first feeding and later nocturnal. It is never found in marshes or swamps, so that attention need not be given to these unless a simultaneous attack on malaria is also desired Epidemic Measures.—(a) Inspection service to detect un reported cases.
(b) Fumigation of houses in which cases have occurred, and also of the adjacent houses.
(c) Removal of patients to screened isolation hospitals.