Yellow fever

Yellow fever is a disease caused by a virus. It spreads when a person is bitten by a mosquito that carries the virus.

Most people with yellow fever feel very sick for a few days. They may have a fever, chills, headaches, nausea, and muscle pains. In some cases, the skin can turn yellow, and there may be other health problems.

The disease is common in parts of Africa and South America. It is rare in Asia. Yellow fever has caused many serious problems in cities, especially in the past, and it still makes many people very sick today.

There is a safe vaccine that protects people from yellow fever. Many countries require travelers to get this vaccine. Stopping the disease also involves keeping the number of mosquitoes low and making sure many people are vaccinated. Doctors can help with the symptoms, but there is no special treatment for the virus itself.

The disease started in Africa and was carried to the Americas a long time ago. It has caused many serious outbreaks around the world. In 1927, scientists were the first to find the yellow fever virus, which helped in learning how to fight the disease.

Signs and symptoms

Yellow fever starts after a few days of feeling unwell. Most people have mild symptoms like fever, headache, chills, back pain, feeling tired, not wanting to eat, muscle aches, nausea, and vomiting. In these cases, the illness goes away in about three to six days.

In some cases, the illness becomes more serious. Fever comes back, and the skin may turn yellow because of problems with the liver. Some people may feel pain in their stomach. Other issues may also happen.

Cause

Yellow fever is caused by a tiny virus. The virus spreads when a special kind of mosquito bites an infected person or animal and then bites another person. This is how the disease moves from one person to another.

Pathogenesis

After a mosquito bites someone with yellow fever, the virus grows in special parts of the body. It then moves to the liver and can damage cells there. This may cause serious problems in the body.

Diagnosis

Yellow fever is found by looking at a person's signs and where they have been. If a person has a fever, pain, nausea, and vomiting after visiting an area with yellow fever, doctors will investigate.

There are special tests that can show if someone has yellow fever. These tests look for parts of the virus or the body's reaction to it. Some tests must wait until a little time has passed after the illness begins. Doctors also need to be sure the illness is not from something else, like malaria or other similar sicknesses.

Prevention

To stay safe from yellow fever, get a vaccination and avoid mosquito bites in areas where the disease is common. Use insect repellent when outdoors, like those with DEET, picaridin, ethyl butylacetylaminopropionate (IR3535), or oil of lemon eucalyptus. Wear long sleeves, pants, and socks. Spray clothes with repellent that has permethrin for extra protection. Mosquitoes that spread yellow fever can bite during the day and at dusk to dawn. Stay in screened or air-conditioned rooms to lower your risk.

Vaccination

Vaccination is the best way to prevent yellow fever, especially for travelers. The vaccine starts working about 10 days after you get it and lasts at least 10 years. The World Health Organization (WHO) suggests that children living in areas with yellow fever get the vaccine between 9 months and 1 year old. Some people might have a mild fever or soreness where they got the shot, but serious problems are very rare.

Vector control

Stopping mosquitoes that carry yellow fever is important because they can spread other diseases like dengue fever and chikungunya disease. These mosquitoes like to breed in standing water, such as old tires, cans, or plastic bottles. To reduce them, remove standing water and use special substances called larvicides or add small fish and copepods that eat mosquito larvae. One good method used in Vietnam uses copepods from the genus Mesocyclops. Another way to reduce adult mosquitoes is using special traps called lethal ovitraps and treating mosquito nets with insecticides. These steps help protect people from diseases spread by mosquitoes.

Treatment

There is no cure for yellow fever, just like with some other infections caused by similar viruses. If someone gets yellow fever, they should go to the hospital. Sometimes, they might need special care because their condition can get worse quickly.

Doctors can help with symptoms. They give fluids to keep the person hydrated and use certain medicines to help with pain. One medicine they use is called paracetamol. They usually don’t give another medicine called aspirin because it can cause problems with bleeding in the stomach.

Epidemiology

Yellow fever is common in tropical and subtropical areas of South America and Africa. Many people live in areas where this disease is found.

Yellow fever mostly occurs in Africa. In 2016, a large outbreak started in Angola and spread to nearby countries. This was stopped by vaccinating many people. In 2016, some cases were reported in China, marking the first time the disease appeared in Asia.

In South America, there are two types of the yellow fever virus. These types likely came from West Africa and were first brought to Brazil a long time ago. In 2016, a big outbreak began in Minas Gerais, a state in Brazil. This outbreak spread among wild monkeys. Health officials started a vaccination campaign to protect people.

Although the main mosquito that spreads yellow fever is also found in parts of Asia, the Pacific, and Australia, the disease had never been reported there until some cases were brought from the 2016 Angola and DR Congo yellow fever outbreak by jet travel.

History

Main article: History of yellow fever

Yellow fever likely started in Africa and spread from animals to humans. It moved to the Americas with the trade of enslaved people. Early outbreaks happened in places like Barbados and the Yucatán Peninsula.

Many places had big problems with yellow fever, especially in warm areas. Outbreaks affected soldiers, cities, and countries. Scientists later learned that mosquitoes spread the disease. This helped control yellow fever in places like Cuba and Panama. Vaccines were developed in the 1930s, which helped reduce the disease.

Today, yellow fever is rare in cities because of vaccines and mosquito control. However, in some areas, especially in Africa, the disease still appears because of challenges with vaccination programs and changes in the environment.

Research

Scientists study yellow fever in animals to find ways to treat it. In one study with hamsters, giving a medicine called ribavirin early helped reduce damage and improved health. This medicine works in a way that might help with another virus called hepatitis C.

Researchers also look at ways to stop yellow fever from spreading. Some countries have studied the disease for other reasons, so it is important to keep research safe and careful.