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1. EPIDEMIOLOGY OF YELLOW FEVER AND ITS
PREVENTION AND CONTROL
BY DR. R. BAMILAN
FIRST YEAR POST GRADUATION
DEPARMENT OF COMMUNITY MEDCINE
STANLEY MEDICAL COLLEGE

2. INTRODUCTION
 Yellow plague, acute viral haemorrhagic disease.
 First zoonotic disease, affects monkey and other vertebrate.
 Clinical features similar to DHF affecting the liver and kidney.
 CFR as high as 80% and death occur within 5 -10 days.

3. PROBLEM STATEMENT
 GLOBAL SCENARIO: International notifiable disease, affects 2 lakhs annually with
mortality of 30,000. Endemic in 44 countries and 110 countries are in risk.
 Evolved in Africa and reached to South America from slave trade 17th century.
 INDIAN SCENARIO: Largest susceptible population, presence of vector, suitable
environment but the agent of yellow fever is missing.
 Effective checking for valid yellow fever vaccination certificate at point of entry, regular
entomological surveillance, expansion of vaccination centres, generating public awareness
and epidemic preparedness strategy are some steps .

4. EPIDEMIOLOGY
 HOST: All ages, both sexes, all occupation related to forest, once infection life long
immunity, infant born to immune mother have antibody for six months.
 AGENT: Flavivirus fibricus, a group B arbovirus from Toga virus family.
 ENVIRONMENTAL FACTORS: More than or equal to 24 degree is needed for
virus to survive and humidity more than 60%.
 SOCIAL FACTORS: Urbanization, Deforestation, Migration, Travel.

5. VECTOR BIONOMICS
 FOREST OF AFRICA: Aedes africans
 SOUTH AMERICA: Haemogogus species
 URBAN AREAS: Aedes aegypti.
 Mosquitoes breed around houses(domestic), forest(wild), both habitats( semi-domestic)

6. TRANSMISSION OF INFECTIONS
 Sylvatic yellow fever: Monkey primary reservoir, passing virus to other
monkeys. Humans working in these forest region can be more risk.
 Intermediate yellow fever: Semi- domestic mosquitoes infect both monkeys and
people. Increased contact between people and infected mosquitoes leads to
increased transmission in humans. Outbreak in adjacent dwellings and villages.

7.  Urban yellow fever: Infected mosquitoes in the urban area transmit the
virus from human to human thus affecting large number of people in
heavily populated areas with high density of mosquito.

8.  Period of Communicability: Man is communicable in the first 3-4 days of illnesss while
monkeys are communicable for several days. African monkey do not die due to yellow fever.
 Extrinsic Incubation: It is 8- 12 days. Mosquitoes are infective for life and show transovarian
transmission similar to dengue.
 Incubation Period: It last for 3- 6 days.

9.  Clinical features: Non specific, abortive illness to fatal hemorrhagic fever.
Starts with abrupt onset of fever, chills , malaise, headache, lower back
ache, myalgia, nausea and dizziness.
Fagets sign may be elicited. Conjunctiva may be congested.
Young children – febrile convulsions.

10.  Lab findings: Leukopenia along with relative neutropenia. Jaundice may develop
between 48 to 72 hrs after the onset and rise in S. Transaminase level. This may
last for several days followed by remission.
 In approx. 15- 20% illiness reappears in more severe form with fever, epigastric
pain, jaundice, renal failure, vomiting and hemorrhagic diathesis( petechiae,
ecchymoses, epistaxis, bleeding gum)

11.  Lab abnormalities: reduced platelet count, prolonged clotting and prothrombin times,
reduced fibrinogen and factors 2, 5,78,9 and 10 and the presence of fibrin split suggesting
consumption coagulopathy.
 About 20-50 % with hepato-renal disease die, typically 7- 10days after the onset.
 True yellow fever viral encephalitis is rarely seen.

12.  Treatment: No specific treatment, symptomatic measures and close monitoring the
symptoms.
Certain medication should be avoided like Dengue, may increase the risk of bleeding.
Prevention and control of yellow fever: Vaccination, vector control, coupled with
surveillance.

13. Vaccination: 17D vaccine is freeze dried, live attenuated and heat sensitive.
Single dose Sub- cutaneous 0.5 ml, deltoid. Use within 30 mins after opening.
Immunity develops after 7th day and remain throughout the life. From 11th JULY
2016, the certificate is vaild for throughout the life. Avoid during pregnancy and
infancy less than nine months. Cholera vaccine also required for international
travel at the same time, 3 weeks apart. Validity of vaccine is from 10 days of
vaccination to the life of the person vaccinated.

14.  Vector control Measures:
Vector surveillance for Aedes aegypti and other Aedes species will be helpful.
Protective measures of personal . Integrated approach of vector control such as source
reduction, spraying aircrafts and ships with insecticides. Aedes aegypti index maintained
below 1% in 400 mts surrounding the Airports and Seaports.

15.  Surveillance:
Clinical or serological or histopathological or entomological
surveillance are required.
 Entomological Indices:
House Index, Container Index, Breteau Index, Aedes aegypti
index. Pupa Index, Adult landing or biting rate.

16.  CURRENT APPROACHES:
Global level: EYE 2017-2026( Eliminate Yellow fever Epidemics) by WHO
along with GAVI and UNICEF
 1. Protect at risk population
 2. Prevent international spread
 3. Contain outbreak rapidly.

17. NATIONAL LEVEL:
Point of Entries Health organization is to prevent spread of disease from foreign
countries and from India to other foreign countries. Safe healthy Environment.
1. International passengers- Screening, history of travel to Yellow fever Endemic
region
2. Indian Aircraft Rules 1955- Vaccination certificate
3. NVBDCP 400mts radius free zone of mosquitoes.

18. REFERNCE
IAPSM’s TEXT BOOK OF COMMUNITY MEDICINE- 2nd Edition

19. THANK YOU