Signs and symptoms

Many Yellow Fever symptoms are mild and can go unrecognised. Early signs of a more severe infection include high fever, headaches, chills, vomiting and characteristic muscle pain, often with permanent backache. The high fever is paradoxically often associated with slow pulse. Symptoms tend to kick in within 3 to 6 days of an infection and after 3 to 4 days, most patients will improve and the symptoms disappear.

More severe are the second round of symptoms and around 15% of patients will advance into this toxic stage, usually within 24 hours. Noticeable warning signs are bleeding from the nose, mouth, eyes or stomach, as the antibodies attack the blood cells. Blood may also appear in vomit or faeces. Kidney function deteriorates, indicated by abnormal protein levels in the urine to complete kidney failure and no urine at all. The patient's skin and whites of the eyes turn the characteristic jaundice yellow, caused by liver failure. Around 50% of patients who enter the toxic phase die, usually within 10-14 days.