The A to Z of yellow fever

Yellow fever is a disease found in tropical and subtropical areas of Africa and South America. It is a viral infection spread by mosquitoes; it can result in illness and even death. It is called “yellow fever” because the skin turns yellow as a complication of the disease (jaundice).

There are currently 43 countries where yellow fever has been declared a risk. Proof of vaccination for travel may be required if you are travelling to or from one of these countries, with many other countries also requiring vaccination for entry.

In Africa: Angola, Benin, Burkina Faso, Burundi, Cameroon, Central African Republic, Chad, The Democratic Republic of Congo, Ivory Coast, Equatorial Guinea, Ethiopia, Gabon, Gambia, Ghana, Guinea, Guinea-Bissau, Kenya, Liberia, Mali, Mauritania, Niger, Nigeria, Rwanda, Senegal, Sierra Leone, South Sudan, Sudan, Togo and Uganda.

And in the rest of the world: South America, Argentina – Misiones Province, Bolivia, Brazil, Columbia, Ecuador excluding Galapagos Islands, French Guiana, Panama, Peru, Paraguay, Trinidad and Venezuela.

In mild cases, yellow fever causes a fever, headache, nausea and vomiting. But yellow fever can become more serious, causing heart, liver and kidney problems along with haemorrhaging. Up to 50% of people with the more-severe form of yellow fever die.

There’s no specific treatment for yellow fever. But getting a yellow fever vaccine before travelling to an area in which the virus is known to exist can protect you from the disease. Before travel, four weeks or more before your trip, make an appointment to visit a travel clinic if you’re travelling 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 travelling to an area where yellow fever occurs. Your travel doctor will help you determine whether you need vaccinations and can provide general guidance on protecting your health while abroad.

Seek emergency medical care if you’ve recently travelled to a region where yellow fever is known to occur and you develop signs or symptoms of the toxic phase of the disease.

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Symptoms

You will not experience any symptoms within the first three to six days after you’ve contracted yellow fever. After this, the infection enters an acute phase and then, in some cases, a toxic phase that can be life-threatening.

The symptoms in acute phase usually improve and are gone within several days.

Acute phase

• 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

Toxic phase

In 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

Causes

It is caused by a virus that is spread by the Aedes aegypti mosquito. These mosquitoes breed even in the cleanest water and are found near where people live.

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.

Risk factors

You may be at risk of the disease if you travel to an area where mosquitoes continue to carry the yellow fever virus. These areas include sub-Saharan Africa and tropical South America.

If you’re planning on travelling to these areas, you can protect yourself by getting a yellow fever vaccine at least several weeks before travelling.

Anyone can be infected with the yellow fever virus, but older adults are at greater risk of getting seriously ill.

Complications

Yellow fever results in death for 20 to 50% of those who develop severe disease. Complications include kidney and liver failure, jaundice (yellow skin and eyes), delirium and coma.

People who survive the infection recover gradually over a period of several weeks to months, usually without significant organ damage. During this time a person may experience severe fatigue and jaundice.

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Prevention

Vaccination

A highly effective vaccine exists to prevent yellow fever. If you plan to travel in these areas, talk with your doctor at least 10 days, but preferably three to four weeks, before your trip begins.

Many countries will require you to present a valid certificate of immunization before allowing you in.

Just one dose of the yellow fever vaccine provides protection for at least 10 years. Side effects are usually mild, lasting five to 10 days, and may include headaches, low-grade fevers, muscle pain, fatigue and soreness at the site of injection.

More significant reactions occur in infants, immunecompromised people, pregnant women and adults older than 60 years and they include developing a syndrome similar to actual yellow fever, inflammation of the brain (encephalitis) or death.

Mosquito protection

In addition to getting the vaccine, you can help protect yourself against yellow fever by protecting yourself against mosquitoes.

• Use mosquito repellents, on own skin and clothing. Avoid applying any repellent on the hands of young children or on infants under two months of age. Instead, cover your infant’s stroller or playpen with mosquito netting when outside.
• Avoid unnecessary outdoor activity when mosquitoes are most active.
• Wear long-sleeved shirts and long pants when you go into mosquito-infested areas.
• Stay in air-conditioned or well-screened housing.
• If your accommodations don’t have good window screens or air-conditioning, it is a good idea to use bed nets. Nets that have been pre-treated with insecticide offer additional protection.