 |
Yellow fever, caused by yellow fever virus (YFV), is a
tropical disease that is spread to humans by infected mosquitoes. The
“yellow” in the name is explained by the jaundice that affects some
patients, causing yellow eyes and yellow skin. While yellow fever is
preventable by immunization, it still causes hundreds of thousands of cases
of disease in Africa and South America.
Many yellow fever infections are mild, but the disease can cause
severe, life-threatening illness.
The virus remains silent in the body during an incubation
period of three to six days. There are then two disease phases. While some
infections have no symptoms whatsoever, the first, "acute", phase is
normally characterized by fever, muscle pain (with prominent backache),
headache, shivers, loss of appetite, nausea and/or vomiting.
Often, the high fever is paradoxically associated with a slow pulse.
After three to four days, most patients improve and their symptoms
disappear. However, 15% enter a
"toxic phase" within 24 hours. Fever reappears and several body systems are
affected. The patient rapidly develops jaundice and complains of abdominal
pain with vomiting. Bleeding can occur from the mouth, nose, eyes and/or
stomach. Once this happens, blood appears in the vomit and feces. Kidney
function deteriorates; this can range from abnormal protein levels in the
urine (albuminuria) to complete kidney failure with no urine production (anuria).
Half of the patients in the "toxic phase" die within 10-14 days. The
remainder recover without significant organ damage. |
