Yellow Fever
Yellow fever is a potentially fatal viral infection transmitted by mosquitoes. There are about 200,000 new cases of this illness diagnosed annually, most of them in South America and Africa, and the number seems to be increasing. When contracted by humans, yellow fever can be a relatively short-lived illness, but in some cases may worsen, causing damage to internal organs, most often the liver. The risk to travelers from the United States and Europe is fairly low, particularly since there is a vaccine available to protect travelers.
Transmission of Yellow Fever
Yellow fever is found most often in countries with tropical climates. In the overwhelming majority of cases, the disease is spread through a few different species of infected mosquitoes, some that live in jungles and some that inhabit urban areas. While yellow fever can't be spread through personal contact, in some instances it can be transmitted through infected blood or through monkeys.
Symptoms of Yellow Fever
The two most noticeable symptoms of yellow fever, which usually appear within a few days of infection, are the ones from which the illness derives its name: fever and the jaundice that sometimes results from liver damage. There are three phases of yellow fever.
Stage 1
During the first stage, the patients exhibits symptoms typical of a great many viruses, including:
- Fever
- Chills
- Headache
- Vomiting
- Muscle aches
Stage 1 usually lasts from 3 to 4 days after which patients improve considerably.
Stage 2
Stage 2 is a period of remission, lasting for about 48 hours. For most patients, this recovery is permanent, but, for an unlucky 15 percent, this seeming recovery is a gateway to much more severe illness.
Stage 3
For those patients in whom yellow fever progresses to Stage 3, symptoms are much more dire. At this point, yellow fever has become viral hemorrhagic fever. The symptoms of Stage 3 yellow fever include:
- High fever
- Jaundice
- Hepatitis (inflammation of the liver)
- Vomiting blood
- Shock
- Failure of heart, lungs, kidneys, liver
For approximately half the patients whose yellow fever progresses to Stage 3, the disease is fatal.
Treatment of Yellow Fever
There is no specific treatment designed to target the virus that causes yellow fever. It is essential for patients to drink plenty of fluids to avoid dehydration. Medication used to lower body temperature or to relieve body aches should be free of aspirin and NSAIDs to prevent aggravation of bleeding problems. Patients whose yellow fever progresses to Stage 3 should be hospitalized and carefully monitored.
Prevention of Yellow Fever
There are two primary ways to prevent yellow fever: avoiding mosquito bites and being vaccinated against the virus.
Vaccination
The vaccination to prevent yellow fever is not only desirable for individuals who will be traveling to regions where the disease is endemic, but often required. Countries where the disease is prevalent may require an International Certificate of Vaccination for all incoming travelers. Such vaccinations must be repeated every 10 years.
While an excellent method of prevention for most travelers, the yellow fever vaccination is not advisable for individuals who:
- Have compromised immune systems
- Have cancer or thymus problems
- Have recently taken steroids or cancer treatment
- Are allergic to eggs, chicken, or gelatin
- Are pregnant or breastfeeding
- Are younger than 9 months or over 65 years of age
For individuals who cannot be vaccinated against yellow fever for any of the above reasons, it may be necessary to provide proof of exemption to enter affected countries
Preventing Mosquito Bites
There are several measures that can be taken to avoid being bitten by a possibly infected mosquito. Most necessary when individuals travel to regions where such mosquitoes are prevalent, these measures include:
- Using insect repellent containing DEET
- Wearing protective clothing outdoors, especially at dawn or dusk
- Spraying permethrin on clothing or bedding used outdoors
- Keeping window and door screens repaired
- Emptying any standing water
Preventing mosquito bites is crucial to preventing spread of the disease.
Vaccinations and prevention of mosquito bites are necessary not only to prevent individual cases and local outbreaks, but to avoid spreading the infection to other parts of the world.