an overview of yellow fever including epidemiology,Clinical features,diagnosis ,management and prevention of yellow .

1. Yellow fever
Melaku Yetbarek( MD,Internist)
November,2023

2. Introduction
• Yellow fever is a mosquito-borne viral
hemorrhagic fever with a high case-fatality rate
• Member of the family Flaviviridae
• Yellow fever virus is a single serotype and is
antigenically conserved
• Yellow fever occurs in tropical regions of sub-
Saharan Africa and South America

5. Transmission Cycle
• The primary transmission cycle involves
monkeys and daytime biting mosquitoes
(Aedes species in Africa, Haemagogus species
in South America).
• Urban yellow fever(Africa)
• Jungle yellow fever(South America)

6. Pathogenesis
• An infected female mosquito inoculates approximately
1000 to 100,000 virus particles intradermally during
blood feeding
• Monocyte-macrophages and large histiocytes, appear
to be the preferred cell types for primary replication
• Large amounts of virus are produced in the liver, lymph
nodes, and spleen
• During the viremic phase (days three to six), infection
may be transmitted to blood-feeding mosquitoes.

7. Pathogenesis
• The midzone of the liver lobule is principally affected
• Injury to hepatocytes is characterized by eosinophilic
degeneration and formation of councilman bodies
• Hemorrhage in yellow fever is as a result of
 Decreased synthesis of clotting factors
 DIC
 Platelet dysfunction

8. Clinical features
• Yellow fever is a typical VHF accompanied by
prominent hepatic necrosis
• Incubation period of 3–6 days
• Nonspecific febrile illness (fatigue, myalgia,
backache, headaches, photophobia, anorexia,
nausea or vomiting)
• About 15% of cases have severe symptoms
including chills, low back pain, headache, and
fever

9. Clinical…
• During this stage, the hepatorenal disease is common
and carries a high mortality.
• A physical exam may reveal the Faget sign or pulse
fever dissociation, facial flushing, and conjunctival
injection.
• During the most toxic phase, patients develop
jaundice, dark urine, and vomiting
• May lead to heptatic failure,AKI,myocarditis and
encephalitis

10. Diagnosis
• Serology(ELISA-presence of IgM antibodies in
a single sample)
• Rapid diagnostic tests-PCR
• Pathology-Postmortem midzone liver necrosis

11. Treatment
• There is no specific treatment, but severe cases require
aggressive supportive care and hydration.
• Patients should be managed in the intensive care unit
(ICU) and closely monitored for
 Disseminated intravascular coagulation (DIC),
 Hemorrhage,
 Kidney, and
 Liver dysfunction.
• Coagulopathy is managed with fresh frozen plasma,
and
• renal failure may require dialysis

12. Prevention
• Control of yellow fever mosquitoes
• Live attenuated vaccine
 Starts with in 10 days and protective for 25-35
years
Contraindicated for <6 month age group
Benefit-Risk assessment before for age groups>60
and pregnant ladies

13. Outcomes
• Higher mortality is usually in patients with liver
and renal damage.
• Deaths tend to occur within the first 10 days of
the toxic phase.
• Both infants and the elderly are more likely to die
than other individuals
• Approximately 20 to 50 percent of patients who
enter the period of intoxication succumb to the
disease

14. Outcome
Poor prognostic signs include :
• anuria,
• shock,
• hypothermia,
• agitation,
• delirium,
• intractable hiccups,
• seizures,
• hypoglycemia,
• hyperkalemia,
• metabolic acidosis,
• Cheyne-Stokes respirations,
• stupor, and
• coma

15. Thank you!!!