- Clinical science
Yellow fever is an acute viral infection caused by the yellow fever virus. Primates are the main reservoir of the virus, which is usually transmitted through bites from infected mosquitoes. Yellow fever is endemic in large parts of South America and Africa. The incubation period is 3–6 days, and the majority of patients remain asymptomatic or experience only mild symptoms. Symptomatic patients initially present with nonspecific symptoms such as sudden-onset fever, malaise, headaches, chills, nausea, and myalgia. Approx. 15% of symptomatic patients progress to the most serious stage of the disease, which can present with life-threatening hemorrhagic fever and organ failure. There is no causal treatment available, making prevention of crucial importance. A single dose of live-attenuated vaccine provides lifelong protection for most individuals.
- Yellow fever is endemic in tropical regions of South America and Sub-Saharan Africa.
- Asia, Europe, North America, and Australia are free of yellow fever (except for occasional imported cases).
Yellow fever is endemic in large parts of South America and Africa!
Epidemiological data refers to the US, unless otherwise specified.
Pathogen: yellow fever virus (genus Flavivirus)
- Genetics: single-stranded, positive-sense, linear RNA virus
- Appearance: enveloped, icosahedral
- Vectors: mosquitoes; (primarily Aedes aegypti )
- Main reservoir: primates (human and non-human)
- Different transmission cycles (depending on local circumstances and geography)
- Incubation time: 3–6 days
- The majority of infected individuals remain asymptomatic.
In symptomatic patients: classic progression in three stages
Period of infection (3–4 days)
- Sudden onset of fever (up to 41°C, or 105°F)
- Headaches, chills
- Nausea, vomiting
- Period of remission (up to 2 days)
- Easing of symptoms and decline in fever
- Period of intoxication (only in ∼ 15% of symptomatic patients)
- Period of infection (3–4 days)
Most patients remain asymptomatic or experience only mild symptoms!
- Laboratory tests
- Virus detection
- Used for definitive diagnosis (e.g., postmortem)
- Must not be done while the patient has an active yellow fever infection
- May show
The best test to rule out yellow fever infection is PCR, particularly in the absence of overt symptoms such as fever, headaches, and chills!
- Viral hepatitis (e.g., )
- Other (Dengue hemorrhagic fever)
The differential diagnoses listed here are not exhaustive.
- Indication: recommended for individuals (≥ 9 months) traveling to areas where yellow fever is endemic
- A single dose of live-attenuated vaccine is sufficient for most patients and provides life-long protection (administer at least 10 days before travel).
- Absolute contraindications: (also see general )