Yellow dever
DEFINITION
Yellow fever is a viral infection spread by a particular type of mosquito. The infection is most common in areas of Africa and South America, affecting travelers to and residents of those areas.
In mild cases, yellow fever causes fever, headache, nausea and vomiting. But yellow fever can become more serious, causing heart, liver and kidney problems along with bleeding (hemorrhaging). Up to 50 percent of people with the more severe form of yellow fever die of the disease.
There’s no specific treatment for yellow fever. But getting a yellow fever vaccine before traveling to an area in which the virus is known to exist can protect you from the disease.
CAUSES
Yellow fever is caused by a virus that is spread by the Aedes aegypti mosquito. These mosquitoes thrive in and near human habitations where they breed in even the cleanest water. Most cases of yellow fever occur in sub-Saharan Africa and tropical South America.
Humans and monkeys are most commonly infected with the yellow fever virus. Mosquitoes transmit the virus back and forth between monkeys, humans or both.
When a mosquito bites a human or a monkey infected with yellow fever, the virus enters the mosquito’s bloodstream and circulates before settling in the salivary glands. When the infected mosquito bites another monkey or human, the virus then enters the host’s bloodstream, where it may cause illness.
SYMPTOMS
During the first three to six days after you’ve contracted yellow fever — the incubation period — you won’t experience any signs or symptoms. After this, the infection enters an acute phase and then, in some cases, a toxic phase that can be life-threatening.
Acute phase
Once the infection enters the acute phase, you may experience signs and symptoms including:
- Fever
- Headache
- Muscle aches, particularly in your back and knees
- Sensitivity to light
- Nausea, vomiting or both
- Loss of appetite
- Dizziness
- Red eyes, face or tongue
These signs and symptoms usually improve and are gone within several days.
Toxic phase
Although signs and symptoms may disappear for a day or two following the acute phase, some people with acute yellow fever then enter a toxic phase. During the toxic phase, acute signs and symptoms return and more-severe and life-threatening ones also appear. These can include:
- Yellowing of your skin and the whites of your eyes (jaundice)
- Abdominal pain and vomiting, sometimes of blood
- Decreased urination
- Bleeding from your nose, mouth and eyes
- Slow heart rate (bradycardia)
- Liver and kidney failure
- Brain dysfunction, including delirium, seizures and coma
- The toxic phase of yellow fever can be fatal.
When to see a doctor
Before travel
Four weeks or more before your trip, make an appointment to see your doctor if you’re traveling to an area in which yellow fever is known to occur so that you discuss whether you need the yellow fever vaccine.
If you have less than four weeks to prepare, call your doctor anyway. Ideally, you’ll be able to be vaccinated at least three to four weeks before traveling to an area where yellow fever occurs to give the vaccine time to work. Your doctor will help you determine whether you need vaccinations and can provide general guidance on protecting your health while abroad.
After travel
Seek emergency medical care if you’ve recently traveled to a region where yellow fever is known to occur and you develop signs or symptoms of the toxic phase of the disease.
Call your doctor if you develop mild symptoms, after traveling to a region where yellow fever occurs.
