yellow fever.pptx

Yellow fever

1. Arun Kumar Parthasarathy Yellow Fever

2. Introduction Yellow fever is an acute, febrile illness; severe cases are characterized by liver dysfunction which leads to jaundice ( hence the name yellow fever ), Renal dysfunction and hemorrhage with high mortality

3. Morphology Yellow fever Virus is an arbovirus Family:- Flaviviridae , Genus:- Flavivirus Enveloped, spherical particles 50nm in diameter with icosahedral nucleocapsid symmetry and surface projections Nucleic acid:- Linear, positive-sense, single-stranded RNA, ~11kb long

4. Typing Seven genotypes have been identified based on the genomic sequence 2 genotypes in South America (South America I and II)and 5 genotypes in Africa, namely, West Africa genotype I (Nigeria, Cameroon, and Gabon), West Africa genotype II (Senegal, Guinea, Ivory Coast, and Ghana), East and Central African genotype (Sudan, Ethiopia, Central African Republic, and Democratic Republic of Congo), East African genotype (Kenya), and Angola genotype (Angola)

5. Transmission Vector:- Aedes aegypti or the tiger mosquito Transmission Cycle:- 1. Jungle cycle – between monkeys and forest mosquito 2. Urban Cycle- between humans and urban mosquito ( Aedes aegypti )

6. India Yellow fever has not invaded yet Measures in India:- Govt. of India has laid down strict guidelines for vigilance and quarantine of the travelers in the International airports. Unprotected (unvaccinated) travelers coming from endemic zone to India will be kept in quarantine for the longest incubation period; i.e. 6 days Breteau index or the Aedes aegypti index should be less than one, surrounding 400 meter of an airport. B.I = No. of containers showing breeding of Aedes aegypti larvae/ No. of houses surveyed X 1000).

7. Clinical Manifestation Incubation period- 3-6 days Febrile illness occurs in early stages of the disease and characterized by Presence of fever, chills, headache, dizziness, myalgia and back ache – followed by nausea, vomiting and relative bradycardia Patient is viremic in this stage and may be a source of infection for mosquitoes.

8. Cont. Severe cases are characterized by 1. Hemorrhagic manifestations 2. Platelet dysfunction 3. Features of Liver involvement (Hepatitis) a. Mid-Zonal necrosis and presence of councilman bodies b. Intranuclear inclusion may be seen inside the hepatocytes called Torres bodies c. Appearance of jaundice 4. Renal dysfunction 5. Encephalitis occurs very rarely 6. Morality rate is high (≥20%), especially among children and elderly.

9. Laboratory diagnosis Serology: - IgM ELISA can be done after 3 days of onset of symptoms. Gives false positive results in other flavivirus infections (Dengue, West Nile and Zika virus) People who are vaccinated within 30 days Positive test confirmed by Plaque-reduction neutralization test . – More specific Molecular Method:- RT-PCR detecting specific viral RNA (NS 5 region) in blood are more confirmatory than serology. It should be performed within 10 days of onset of symptoms.

10. Yellow fever Vaccine Yellow fever 17D Vaccine Live attenuated vaccine (Contra indicated in people having allergic to egg) In India, it is prepared in Central Research Institute (CIR), Kasauli . Strict cold chain has to be maintained during the transport ( -30 C to +5C). Available in Lyophilized form, once reconstituted it should be used within ½ hour Vaccine is effective within 7 days of administration, the efficacy lasts for upto 35 years

11. Validity of yellow fever vaccine certificate: issued after 10 days of vaccination and renewed every 10 years. This is the recommendation for international travel. Cholera and yellow fever vaccine interact with each other; hence should not given together (3 weeks gap to be maintained). Contraindications:- Children ≤9 months (≥6 months during epidemic) Pregnancy (except during outbreak) HIV-infected people People with allergy to egg