What should you know about etiology of yellow fever?

A mosquito becomes infected after biting a person or primate carrying the virus, then can pass it to another person through a later bite. Yellow fever does not ordinarily spread through casual contact, food, or water. Risk depends on travel location, mosquito exposure, and local transmission.

Early illness may include fever, headache, muscle aches, nausea, and weakness. Some people improve, but others develop liver injury, jaundice, bleeding, confusion, or organ problems. A traveller's vaccination and itinerary are useful details for a clinician.

If you develop fever during travel or after returning from an area where yellow fever occurs, contact a healthcare professional promptly and describe your destinations and dates. Avoid mosquito bites with long clothing, window screens, and an appropriate repellent so mosquitoes do not pick up the virus from you.

Vaccination is the main preventive measure for eligible travellers. A clinician or travel service can review your itinerary, health history, age, pregnancy status, and any entry requirements before vaccination.

Seek urgent medical care for fever with yellowing of the eyes or skin, dark urine, unusual bleeding, severe abdominal pain, persistent vomiting, confusion, fainting, or marked weakness, particularly after travel in a risk area. Tell the service about recent travel before arrival when possible.

Ask whether your destination carries yellow fever risk, whether vaccination is suitable for you, when it should be given before travel, and how to reduce mosquito exposure. Discuss fever after travel even if you received a vaccine, because other infections can cause similar symptoms.