Yellow fever

Yellow fever : Causes, Symptoms, Diagnosis And Treatment

Yellow fever or YF is a potentially serious flu-like disease caused by mosquitoes. As the name suggests, the disease can cause flu-like symptoms like fever. The disease can cause yellowing of skin and eye (jaundice), which gives the disease its name. This disease is prevalent in different parts of Africa as well as South America. Unfortunately, you have no cure available. So, the only method to avoid complications is to prevent it. With the development of the vaccine, it is now possible to avoid contracting the disease.

History Of Yellow Fever

Yellow Fever virus has its origins in Africa. The slave trade era brought the virus to the western hemisphere. In 1648, Yucatan recorded the first epidemic of YF. Over two hundred years, YF outbreaks occurred frequently in regions like Europe, the coastal cities of North America, and in tropical America. By the 19th century, people became aware of the non-communicable nature of the disease. So, the people discarded the notion that the disease spread from person-to-person. But, theories wrongly suggested the disease occurred due to atmospheric miasmata. Carlos Finlay from Cuba in 1881 suggested the mosquito transmission of the disease. He suggested Culex cubensis (currently known as Aedes aegypti as the mosquito genus responsible for spreading the infection from one person to another.

Yellow Fever virus

Despite his efforts, Carlos Finlay never managed to prove his theory. But, his efforts served as the foundation for the research conducted by U.S. Army surgeon Major Walter Reed. He, along with James Carroll (one of a member of United States Army Yellow Fever Commission). Reed’s discovery is one of the most important contributions of the medical field as well as human history.

About Yellow Fever

Yellow Fever refers to the viral infection caused by a specific type of mosquitoes. It mostly affects people visiting or residing in African countries and South American countries. When you suffer from a mild form of the infection, it causes discomfort in your body by triggering, headache, liver, and kidney problems. Some people can also experience hemorrhaging (bleeding). But, others suffer from a severe form of the disease, resulting in organ damage and subsequent death. Since the condition has no specific cure, you need to take vaccination before visiting the areas prone to the YF outbreak. It protects you from contracting the disease.

Symptoms Of Yellow Fever

Symptoms Of Yellow Fever

The symptoms triggered by the viral infection differs from the stages of YF. In most cases, people may not see any signs during the incubation period (first three to six days after the infected mosquito bite). After the incubation period, the infection goes through different phases. Let’s see the other phases in detail:

Acute Phase Of Yellow Fever

An infected person enters the phase after the incubation period. During the phase, you may experience the following signs:

  • Fever
  • Muscle aches (specifically in your knees and back)
  • Headache
  • Sensitivity to light
  • Loss of appetite
  • Nausea/vomiting or both
  • Loss of appetite
  • Red eyes
  • Face or tongue appears red
  • Dizziness

With supportive care, these symptoms improve. So, they are gone within a span of several days.

Toxic Phase Yellow Fever

For some people, signs, and symptoms associated with YF disappear after a day or two. So, following the acute phase, most people get relief from the infection. But, some people enter a toxic phase. During the phase, the infected person can suffer from severe and life-threatening symptoms. You need to look out for the following signs:

  • Jaundice (Yellowing of whites of eyes and skin)
  • Decreased urination
  • Abdominal pain
  • Bleeding from your mouth, eyes, and nose
  • Presence of blood in vomit
  • Liver failure
  • Slow heart rate (bradycardia)
  • Kidney Failure
  • Brain dysfunction (it can cause seizures, delirium, and coma)

The toxic phase of YF can prove fatal.

When To See A Doctor?

Many people wonder when you need to see a doctor. It is important to note that you have to see a healthcare professional in the following cases:

Before Traveling To Yellow Fever Prone Areas

If you are planning to visit areas with the YF outbreak, then you need to make an appointment with your doctor. At least four weeks before or earlier the travel date, you need to see a doctor discuss the vaccine. Your doctor suggests if you need the vaccine or not. People who have less than four weeks before travel should also make it a point to see their doctor. It is ideal to take the vaccination at least three to four weeks before the travel as it gives time for the vaccination to work. When you discuss the options with your doctor, you get guidance regarding the need for vaccination as well as the necessary guidance to protect your health when you are abroad.

After Traveling To Yellow Fever Affected Areas

If you recently traveled to a location with known cases of yellow fever or prone to outbreaks, then see a doctor. It is also essential when you see the signs and symptoms associated with the infection. Get immediate medical help before the condition escalated to the toxic phase. Consult your doctor even when you see mild symptoms associated with the disease after your travel to areas known for YF outbreaks.

Causes Of Yellow Fever

Yellow Fever is triggered due to the virus, which is spread from one person to another by the mosquito of the Aedes aegypti genus. These mosquitoes breed and thrive near human habitation. It is not necessary that the mosquitoes will only thrive in contaminated water as they can breed even on clean water. The mosquitoes infect both monkeys and humans with the YF virus. The mosquitoes transmit the YF virus back and forth between humans and monkeys or both.

When the  Aedes aegypti mosquito bites a monkey or human infected with YF virus, the virus enters the bloodstream of the mosquitoes. It starts circulating in the bloodstream of the mosquito and finally settles in the salivary gland. It results in the mosquito becoming infected. When the infected mosquito bites another human or monkey, it transfers the virus into the host’s bloodstream. So, it results in developing a viral infection.

Risk Factors Associated With Yellow Fever

Not everyone is at risk of getting YF infection. It only affects people who come in contact with mosquitoes carrying the YF virus. So, the infection risk increases when you visit or reside in tropical South America and sub-Saharan African regions. While the outbreaks have reduced considerably in recent years, the risk still exists. The cases have decreased due to the increased vaccination rates among the residents. So, they are protected from the disease. The reduction in the number of cases can also mean the failure to report the infection officially. So, the following people face a higher risk of contracting yellow fever:

  • People who travel overseas without getting a vaccination.
  • Older people

Make sure you get vaccination several weeks before the trip for it to take effect. See your doctor before the trip to get the necessary advice to avoid the infection.

Transmission Of Yellow Fever

The virus causing YF belongs to the Flavivirus genus. The arbovirus transmits through mosquito bites. But, never think all mosquitoes spread the disease. Only mosquitoes belonging to Haemogogus and Aeges species transmit the virus from one person to another. Since the different mosquito species live in different habitats, the transmission cycle also varies. The breeding habitats of mosquitoes vary as some breed around the houses (domestic) while other breeds in forest/jungle (wild). Some mosquitoes breed in both domestic and wild habitats (semi-domestic). The three transmission cycle includes:

Sylvatic/Jungle Yellow Fellow

The transmission cycle includes monkeys residing in the tropical rainforest (it acts as the primary reservoir of YF). The monkeys bitten by the wild mosquitoes of Haemogogus and Aedes species pass the virus to its fellow monkeys. When humans working or traveling to the tropical forest get the infection through mosquito bites. So, they end up developing YF.

Intermediate Yellow Fever

In such a type of transmission cycle, the semi-domestic mosquitoes pass the infection. Such infection breeds in the wild as well as around common households. These mosquitoes bite both monkeys as well as people. The increase in contact between people and mosquitoes carrying the virus rises the transmission rates. It results in different villages in a specific area developing outbreaks at the same time. Such type of transmission causes frequent and common outbreaks in Africa.

Urban Yellow Fever

Large epidemics of the disease occurs when infected people introduce the virus to a hugely populated area with a high density of mosquitoes of Aedes aegypti genus as well as contain people with little or no immunity. No immunity occurs due to prior exposure to YF or a lack of not getting the vaccination. In such cases, the infected mosquitoes transmit the virus from one person to another.

Complications Due To Yellow Fever

Small children and people over 50 years develop severe symptoms due to YF. Around 20% to 50% of the people who suffer YF succumb to death. Therefore, people coming under the suggested age group need to maintain caution. The people coming under the high-risk category of developing the disease need to follow the steps to prevent the disease. A person affected by yellow fever during the toxic phase can suffer from the following complications:

  • Kidney failure
  • Jaundice
  • Liver failure
  • Delirium
  • Coma

People who survive YF recover gradually over a period of time. It takes several weeks to months to bounce back. So, a person suffering from the infection can get back to their normal health without suffering significant organ damage. But, during recovery, the infected person can feel extreme tiredness and jaundice. Other complications of secondary bacterial infections like blood infections or pneumonia.

Diagnosis Of Yellow Fever

Diagnosing YF in the early stages can become a problem for your doctor. It is because the signs and symptoms of the infection mimic several other diseases like:

  • Malaria
  • Dengue
  • Viral hepatitis
  • Typhoid
  • Leptospirosis (specifically fulminant forms)
  • Poisoning
  • Other viral hemorrhagic fevers

Therefore, it is essential to eliminate the chances of other diseases before coming to a conclusion. To make a proper diagnosis, your doctor can use the following steps:

Medical And Travel History

When you see the symptoms, consult your doctor. Your doctor can ask a question regarding your medical history and recent travels. If you have traveled to a YF outbreak prone area, then you need to inform the doctor. It helps with diagnosing the condition quicker.

Blood Testing

You need to provide blood samples to undergo certain tests to conclusively detect the presence of the YF virus. The technician takes a sample of you and sends it to the lab for testing. The blood test can either find the presence of the virus or detect antibodies as well as substances specific to the YF virus. For detecting the presence of the virus in the early stages of the disease, your doctor suggests PCR (Polymerase Chain Reaction) test in the blood. The blood sample is also collected to detect the antibodies during the later stages of the disease. For detecting the presence of YF virus in advanced stages, your doctor suggests the following tests:

  • PRNT

Urine Test

A sample of your urine can help the doctor detect the presence of the YF virus. The PCR test using a urine sample can also detect the virus during the early stages of the disease.

Treatment For Yellow Fever

No specific cure is available for yellow fever as an antiviral medication offers no help. So, your doctor suggests supportive care to ease the symptoms and make you feel less distressed. Your doctor takes the following steps to alleviate the condition.


Before starting any treatment, your doctor may suggest isolating yourself. If you have a mild case of the disease, then you just need to stay inside your home. It is to prevent any contact with the mosquitoes that can transmit the disease to others.

Maintain Hygiene

Keep your surroundings clean to avoid breeding of mosquitoes that can transmit the infection from one person to another. Eliminate the breeding grounds to avoid the spreading of the infection.

Enhance Immune System

Since you have no cure for the condition, the treatment focuses on aiding your immune system to fight off infection. Supportive care includes the following:

  • Overcome dehydration and malnutrition by providing necessary fluids through veins (intravenously).
  • Offer oxygen to maintain the balance in your body.
  • Check blood pressure constantly to maintain a healthy level.
  • To overcome blood loss, get blood transfusions.
  • Undergo plasma transfusion to replace the blood protein for improving blood clotting.
  • Treat any infection you develop due to YF fever to avoid any distress.

Preventing Yellow Fever

Can you prevent yellow fever? Yes, it is possible to prevent the infection by maintaining caution. Wondering how? Here are the steps to avoid viral infection:

Get Vaccination

One of the most effective steps to avoid YF infection is by getting the vaccination. The highly effective vaccination can prevent the infection from affecting you. The condition mostly affects people living or traveling to sub-Saharan Africa as well as certain parts of South America. So, people who live or travel to these parts need to talk to the doctor regarding getting the YF vaccine. You need to get the vaccination at least ten days, but before three to four weeks before traveling. Some countries in the region have imposed the necessity of submitting a valid certificate of immunization for travelers when they enter the country.

A single dose of YF vaccine can offer protection from the infection for at least ten years. If you fear the side effects associated with the vaccination, then never worry as it causes only mild symptoms like:

  • Low-grade fevers
  • Headache
  • Fatigue
  • Muscle pain
  • Soreness at the injection site

In some rare cases, some people develop severe complications like encephalitis (inflammation of the brain) or develop a syndrome similar to YF. But, the vaccination is safe for people between the ages of nine months to sixty years. It is better to talk to your doctor if YF is ideal for you or your child younger than nine months. Consult your doctor regarding the YF vaccination when you come under any of the risk cases:

  • Are pregnant
  • Have a weak immune system due to disease or side effects of medication (immunocompromised)
  • Older than sixty years

Protection From Mosquito Bites

Apart from getting a vaccination to get adequate protection from the YF virus, you also need to take steps to protect yourself from a mosquito bite. So, if you are traveling to a location prone to YF outbreaks, then take the following steps to reduce your exposure to mosquitoes:

Limit Activities

Try to reduce or avoid unnecessary outdoor activities in areas known for mosquito habitat or during the time the mosquitoes are most active.

Opt For Ideal Dress

Wear a dress that covers your whole body. It reduces skin exposure causing mosquitoes to gain easy access to your skin surface. So, when you visit mosquito-infested areas, wear a long-sleeved dress as well as long pants.

Choose Rooms With Caution

Since mosquitoes cannot dwell in cooler regions, stay in an air-conditioned room. If you cannot find such rooms, try to opt for well-screened housing that prevents the entry of mosquitoes.

Use Bed Nets

If your accommodations don’t have good window screens or air-conditioning, use bed nets. Nets that have been pre-treated with insecticide offer additional protection.

Use Mosquito Repellents

To ward off mosquitoes, you need to use a Mosquito Repellents. The repellent offers a protective barrier to the skin. So, it prevents mosquitoes from biting the exposed part of your skin. You have different options available like:

Non-skin Repellent

You can use permethrin-containing mosquito repellent that you can apply on your clothes, shoes, bed netting, and camping gear. Instead of using the product directly on your skin, you can apply these products to the accessories you use. You can also opt for permethrin pre-treated clothing or gear. Permethrin is not suitable to use on your skin.

Skin Repellent

Some of the products containing active ingredients like DEET, Picaridin or IR3535. The products containing such items offer long-lasting protection from mosquito bites. You have to spend some time deciding on the right concentration based on the hours of protection needed. So, the higher concentration of the product offer lasting protection. You need to understand that chemical repellents can cause toxic effects. So, choose the amount needed for the time you remain outdoors. Avoid using DEET on hands-on young children or infants under two months of age. You can use mosquito netting to cover the infant’s stroller as well as a playpen when you go outside.

You can use natural products to avoid mosquito bites. So, use natural products like lemon eucalyptus that offers the same protection as DEET when you use similar concentration. But, avoid using it on children younger than three years.


Yellow fever cases have now reduced drastically due to the introduction of the vaccine. Before the introduction of the YF vaccine, the main method to stop the spread of the disease is by preventing the breeding of Aedes aegypti. Since the people who travel to the outbreak are prone to the infection. So, it is important for travelers to talk to the doctor about vaccination or other methods to avoid mosquito bites. Since the infection has no specific treatment, you need to take care not to get exposed to mosquito causing the problem. Take ample precautions when you travel to avoid distress.

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