Yellow Fever: Causes, Symptoms and Treatments

Yellow fever is a viral infection transmitted by the bite of infected mosquitoes most commonly found in parts of South America and Africa. When transmitted to humans, the yellow fever virus can damage the liver and other internal organs and be potentially fatal. The World Health Organization estimates that there are 200,000 cases of yellow fever worldwide each year, resulting in 30,000 deaths. Yellow fever appears to be on the rise internationally, due to decreased immunity to infection among local populations, deforestation, climate change, and high-density urbanization.

What is the Risk of Yellow Fever:  The CDC has identified 44 counties with a risk of yellow fever transmission , many of them with tropical climates. Although the actual number of yellow fever cases among American and European travelers to these at-risk countries is low, vaccination is advised for most international travelers to these countries because yellow fever has no cure and can be deadly.

How Yellow Fever is Spread: Yellow  fever is typically spread to humans from bites by infected mosquitoes. People cannot spread yellow fever among themselves through casual contact, although the infection can be transmitted directly into the blood through contaminated needles.

A few different species of mosquitoes transmit the yellow fever virus ; Some breed in urban areas, others in jungles. Mosquitoes that breed in the wild also transmit yellow fever to monkeys, which, in addition to humans, are hosts of the disease.

Symptoms of Yellow Fever: Yellow  fever gets its name from two of its most obvious symptoms: fever and yellowing of the skin. Yellowing occurs because the disease causes liver damage , hepatitis . For some people, yellow fever has no initial symptoms, while for others, the first symptoms appear three to six days after exposure to the virus from a mosquito bite.

A yellow fever infection typically has three stages. The first phase of symptoms can last for three to four days and then, for most people, disappears. The first stage is usually non-specific and cannot be distinguished from other viral infections.

The initial symptoms of yellow fever are:

• Fever and Chills:  Symptoms such as muscle aches, headaches and vomiting
• The next phase is remission, which lasts for 48 hours. Patients get better. Most recover.
• Unfortunately, a third, more toxic phase of infection occurs for 15% to 25% of patients. Ultimately, a condition called viral hemorrhagic fever can develop, with internal bleeding (hemorrhage), high fever, and damage to the liver , kidneys, and circulatory system. The World Health Organization estimates that up to 50% of people worldwide who reach this severe stage of the infection die, while half recover.

Symptoms of third stage yellow fever can include:

• Jaundice (liver damage), which causes yellowing of the skin and eyes
• Hepatitis (inflammation of the liver)
• Internal bleeding (bleeding)
• blood vomiting
• Shock
• Multisystem organ failure leading to death

How Yellow Fever is Diagnosed:  Yellow fever is diagnosed by its symptoms, recent travel activity, and blood tests. Yellow fever symptomscan mimic the symptoms of other tropical diseases such as malaria and typhoid, so contact your doctor if you have yellow fever symptoms and have recently traveled to a high-risk country.

How Yellow Fever is Treated:  Because there is no cure for the viral infection itself, medical treatment of yellow fever focuses on alleviating symptoms such as fever, muscle aches, and dehydration. Because of the risk of internal bleeding, avoid aspirin and other nonsteroidal anti-inflammatory drugs if you suspect you have yellow fever . Hospitalization is often necessary.

Prevention of Yellow Fever Through Vaccination:  Because there is no cure for yellow fever , prevention is critical.  The yellow fever vaccine is recommended for adults and children over the age of 9 months who travel to or live in countries with a known risk of yellow fever . Certain countries in Africa and Latin America with a higher risk of exposure to yellow fever now require proof of a yellow fever vaccination before allowing you to travel there.

Medical clinics and state or local health departments often offer the vaccine, which needs to be repeated every 10 years for people traveling to high-risk areas. These approved vaccination centers can also provide you with the International Certificate of Vaccination that you will need to enter certain countries at risk.

Call your doctor right away if you develop symptoms such as a fever, flu, or other unusual signs after getting the vaccine. The yellow fever vaccine , in some rare cases, has caused an allergic reaction, nervous system reaction, and life-threatening illness.

Who Should Not Get Vaccinated for Yellow Fever:  Vaccination against yellow fever is not recommended for everyone. The vaccine can cause serious adverse effects in certain people. Efforts are underway to develop a killed vaccine that will be safer. Talk to your doctor before getting the vaccine if:

• Having a compromised immune system, such as from HIV
• Have cancer or thymus gland problems
• Have had treatment that can disrupt the immune system, such as steroids or cancer treatment
• Have had a life-threatening allergic reaction to past eggs, chicken, gelatin, or yellow fever vaccine
• Are pregnant or breastfeeding
• Are 65 years or older
• Your child is less than 9 months old.

Keep in Mind that Vaccination Has Two Purposes:  To protect the health of individual travelers entering high-risk regions and to protect the public health of countries by preventing the importation of yellow fever into your region. If you are exempt from vaccination for medical reasons, you may need to provide proof of exemption for entry into some countries.

Other Yellow Fever Prevention Measures:  Vaccination is the most important measure you should take when traveling to areas where exposure to the yellow fever virus is possible. No other measure is more effective, but there are other valuable recommendations. You must:

• Use the right insect repellent for mosquitoes on exposed skin and follow the instructions on the package. Buy one with DEET, picaridin, lemon oil , eucalyptus, or an ingredient called IR3535.
• Cover your arms, hands, legs and head to protect yourself from being bitten.
• Use a repellent containing permethrin on the outside of clothing, mosquito nets, and other gear.
• Use screens on windows and doors, and mosquito nets over beds, to keep mosquitoes away.
• Avoid outdoors during peak mosquito hours (dusk to dawn for many types of mosquitoes that carry the infection).
• Keep accurate records of international travel dates, locations, and outdoor activities in case you need to identify a viral infection when you return.