yellow fever
Meaning of yellow fever: Named for the jaundice of its severe phase, though most infections never reach that stage and some produce no illness at all.
Definition of yellow fever
Yellow fever is an infectious disease caused by the yellow fever virus and spread to people by the bite of infected mosquitoes. Many infections cause no illness or only a mild one, with fever, headache, muscle aches, chills and weakness. A minority progress to a severe phase involving bleeding, vomiting, jaundice and organ failure.
How does the illness progress?
| Phase | What happens |
|---|---|
| Incubation | Several days between the bite and any symptoms |
| Acute phase | Fever, headache, muscle and back pain, nausea, loss of appetite |
| Remission | A brief period of improvement, after which most people recover completely |
| Toxic phase | In a minority, fever returns with jaundice, bleeding, abdominal pain and failing organs |
The deceptive part is the remission. Symptoms ease and the illness appears to be over, and only then does the severe phase begin in those who develop it. The liver is the organ most affected, which is where the yellowing of the skin and eyes comes from and where the disease got its name, and the kidneys and clotting system fail alongside it.
How is it transmitted?
The virus circulates between mosquitoes and primates. In forested areas it passes between mosquitoes and monkeys, and people are infected when they enter that environment. In towns and cities a different cycle takes over, running between people and mosquitoes that breed in stored water around dwellings, which is what allows outbreaks to grow quickly in populated areas. The disease does not pass directly from one person to another. It occurs in tropical parts of Africa and of South and Central America, and despite the presence of suitable mosquitoes it has never established itself in Asia.
How is it prevented and identified?
A live vaccine exists and is used both for residents of affected regions and for travelers to them, and proof of vaccination is required for entry to some countries. Mosquito control and avoiding bites reduce transmission where the vaccine is not in use. Diagnosis is difficult early on, because the first phase resembles malaria, dengue, leptospirosis and viral hepatitis, and it rests on blood tests for the virus or for antibodies against it interpreted alongside where the person has traveled. No drug treats the virus itself, so care of severe disease is supportive.
Used in a sentence
The traveler's fever and jaundice raised concern for yellow fever given recent travel to an endemic region.
Good to know
Yellow fever characteristically pauses in a brief period of apparent improvement before the severe phase begins in those who develop it, so early recovery does not confirm that the illness has ended.