What should you know about types of yellow fever?

Yellow fever may cause a mild, short illness or progress to a severe form affecting the liver and other organs. The early symptoms can overlap with other infections, so the pattern of illness and recent travel or mosquito exposure matter when a clinician assesses you.

An initial illness may include fever, headache, muscle aches, chills, nausea, vomiting, and marked tiredness. Some people improve after this early phase. Others develop a more serious illness after a brief improvement, with yellowing of the eyes or skin, dark urine, bleeding, confusion, or reduced urine output. Yellowing reflects liver involvement, while confusion or reduced urine may signal wider organ stress.

Yellow fever is spread by infected mosquitoes, not by ordinary casual contact between people. The diagnosis cannot be made reliably from symptoms alone because several travel-related infections can look similar.

If you become unwell during or after travel to an area where yellow fever occurs, contact a healthcare professional promptly and describe your destinations, dates of travel, mosquito bites, vaccination history, and any medicines taken. Rest, drink fluids if you can keep them down, and avoid further mosquito bites so an infected mosquito is less likely to acquire the virus from you.

For future travel, ask about entry requirements and personal suitability for vaccination well before departure. Use repellent, long clothing, screens, or air-conditioning where available. Read the guidance on Yellow Fever Vaccination for preparation and follow-up planning.

Seek urgent medical care for yellowing of the skin or eyes, unusual bleeding, repeated vomiting, severe abdominal pain, fainting, confusion, extreme drowsiness, breathing difficulty, or very little urine. A fever after travel deserves prompt assessment, especially if symptoms are worsening or you are pregnant, have a weakened immune system, or take medicines that affect the liver or bleeding.

Ask which destinations carry yellow fever risk, whether vaccination is suitable for you, how early it should be arranged, and what symptoms should trigger urgent review after travel. You can also ask how to prevent mosquito bites and whether another travel infection needs testing.