Yellow Fever

1
Yellow Fever

• And other viral hemorrhagic fevers

2
Viral hemorrhagic fevers

• There are several types of VHFs in Ghana,
  although YF is the most prominent
• Lass Fevera, Ebola, Crimean-Congo hemorrhagic
  fever
• Focus of slides is on YF

3
Distribution and incidence

• YF occurs only in South America and Africa
• Resurgence has occurred in last 2y years in West
  Africa (including Ghana) where it is endemic
• Epidemics also occur in urban areas where
  transmission of the virus occurs from human to
  human through the bite of the Ae. Aegypti
  mosquito

4
Transmission and epidemiology

• Ae. Aegypti is found in forest primates (monkeys)
  who serve as viral reservoir
• Spread to humans through bite either in forested
  regions from mosquitoes transmitting from monkeys
  or in urban regions when mosquitoes spread it
  from human to human. There is no direct
  transmission.

5
Vector

• The mosquitoes adapt to villages, breed in cans
  of water, tires, uncovered water storage
• After mosquitoes bite human, he/she become
  viremic for several days. If bitten by another
  mosquito, the virus then grows in the insect for
  about 9-12 days before this second mosquito can
  transmit to another human

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Pathophysiology

• Incubation period is about 3-6 days.
• Virus replicates in lymph nodes, then spreads to
  bone marrow, liver and spleen
• Large amount of liver damage ensues
• Platelet dysfunction
• Hemorrhages throughout bodyespecially GI,
  pleura, brain

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Clinical Manifestations

• Usually self-limited illness, but may be fatal in
  up to half of cases
• Manifested by myalgias, malaise, lethargy,
  prostration, fever, often has an initial
  symptomatic period, followed by remission, then
  severe exacerbation

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Clinical Manifestations

• Other symptoms include vomiting and dehydration
• Jaundice evident along with petechiae, epistaxis,
  purpuric hemorrhages
• Disease progresses to renal failure, liver
  failure, encephalopathy and come
• Death within 7-10 days after onset

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Treatment

• No specific therapy supportive of fluid and
  electrolyte balance life-saving measures

10
Diagnosis

• Important to note if patient has been
  vaccinatedabout 9 of children in Africa have
  been vaccinated. If vaccinated, then suspect
  another type of VHF
• Viral culture confirms DX

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Prevention and Control

• Live attenuated YF vaccine is 95 effective
  within 10 days of inoculation
• Reimmunization required every 10 years for
  travelers