Yellow Fever

Yellow Fever is a viral hemorrhagic fever that is caused by the yellow fever virus, a flavivirus. Mosquito-borne. Endemic in South America and sub-Saharan Africa. The vaccine is protective against all strains. Mortality is 15%.

Causes injury to hepatocytes, myocardium, and kidney and cause circulatory shock. Infectivity- in viremic phase; 3 to 6 days after the bite and lasts 4 to 5 days.

Causes of Yellow Fever

Infection to humans

• When trees are felled or when monkeys raid human settlements.
• Human-to-human transmission is possible.

Clinical presentation of Yellow Fever

Three stages;

1. Infection

• Fever, malaise, headache, anorexia, myalgia, dizziness
• Epigastric tenderness, reddening of conjunctiva and gums
• Tender hepatomegaly

2. Remission

• 48 hours after 1st phase
• Reduction of fever and symptoms
• 15% persist to stage 3

3. Intoxication

• A return of fever, epigastric pain, jaundice, nausea and vomiting, hemorrhagic diathesis
• Multi-organ failure

Differential diagnosis of Yellow Fever

• Malaria
• Typhoid
• Viral hepatitis
• Aflatoxin poisoning
• Leptospirosis
• Hemorrhagic fevers

Diagnosis

1. Detection of the virus through culture or PCR-first 3 to 4 days
2. Serology- IgM or a four-fold rise in IgG
3. Full blood count- leucopenia
4. Immunohistochemistry- for viral antigens
5. Postmortem findings- acute mid-zone necrosis of liver and councilman bodies

Management of Yellow Fever

Supportive is the mainstay.

• Nutrition
• Prevent hypoglycemia
• Treat hypotension
• Oxygen and anticonvulsants
• Fresh frozen plasma for bleeding and dialysis for renal failure
• Manage metabolic acidosis, prevent gastric distention and aspiration
• Isolation.
• ICU care

Prevention

Vaccination- protective for 10 yrs

• When travelling to an endemic area
• Side effects; hypersensitivity, encephalitis, viscerotropic disease
• Contraindicated in; severely immunocompromised and egg allergy