Lesson 43 : Prevention Of Arthropod Borne Infections
Yellow Fever
Yellow fever is a zoonotic disease caused by an arbo-virus. It is transmitted to man by certain culicine mosquitoes. Clinical features are similar to other viral haemorrhagic fevers (e.g., dengue HF,Lassa fever), but is characterized by more severe hepatic and renal involvement. The spectrum of disease varies from clinically intermediate to severe cases. Severe cases develop jaundice with hemorrhagic manifestations and albuminuria or anuria, shock, agitation, stupor and coma.
Epidemiological Determinants:
Agent Factors:
Agent: The causative agent is Flavivirus fibricus.
Reservoir of Infection: in forest areas, the reservoir of infection is monkeys and forest mosquitoes. In urban areas the reservoir is man, besides Aedes aegypti mosquitoes.
Period of Infectivity:
In man: blood of patients is infective for first 3-4 days of illness.
In mosquitoes: after an incubation period of 8-12 days the mosquitoes become infective and remains infective for lifelong.
Host Factors:
Age and Sex: All ages and both sexes are susceptible in the absence of immunity
Occupation: Persons engaged in work involving contact with forest are exposed to the risk of yellow fever.
Climate: A temperature of 24 degree Centigrade and relative humidity of 60 per cent is favourable for the multiplication of the vector.
Social Factors: Urbanization leads to extension of the disease. People moving more close to forest, increasing number of people travelling are risk factors of the disease.
Mode of transmission: There are two cycles of transmission-Jungle cycle and Urban cycle.
Incubation Period: 3 to 6 days
Control: vaccination is the means of control of both Jungle yellow fever and urban yellow fever.
Participants