Causes, Symptoms and Prevention of Yellow Fever

Causes, Symptoms and Prevention of Yellow Fever

“Yellow fever” is a viral infection which is transmitted by the bites of the infected mosquitoes. Yellow fever gets its name from its common symptoms which are the yellowing of the skin and fever. Mostly, this infection is found in the parts of Africa and South America which affects the residents and travelers. Yellow fever virus can cause severe damage to the liver and other internal organs. Its infection can be potentially fatal.

In some cases, yellow fever causes mild symptoms like nausea, headache, fever, and vomiting. In other cases, yellow fever can become fatal, causing liver, heart and kidney problems.

No specific treatment is available for yellow fever. However, vaccines are available. One should get a vaccination of yellow fever before traveling to an area where yellow fever viral infections are already found.

Transmission of Yellow Fever virus

Generally, the yellow fever virus is transmitted to humans via the bites of infected mosquitoes.

Yellow fever virus cannot be transmitted via casual contact. The transfusion of infected blood or the use of contaminated needles can cause the transmission of infection.

A few species of mosquitoes can transmit the yellow fever virus (some breed in jungles, while others in urban areas). These mosquitos transmit the virus to humans. Humans are not the only host for this disease. The Mosquitoes that breed in the jungle also transmits yellow fever virus to monkeys. Both the human and monkey are a host for this disease while mosquitos are the vector for transmission.

Symptoms of Yellow Fever 

Yellow fever causes various symptoms. The incubation period of yellow fever is three to six days during which some patients experience signs or symptoms while others don’t experience any symptom.

Typically, yellow fever has three phases which are the following:

First phase

During the first phase, mild symptoms appear which usually lasts for three to four days and then, disappears in most people. The first phase of infection is non-specific and cannot be easily distinguished from other viral infections.

The initial symptoms of yellow fever are:

  • Flu-like symptoms such as headache and muscle aches
  • Chills and Fever
  • Vomiting

Acute phase

After the initial phase, the infection enters the acute phase. During the acute phase, the patient may experience following signs and symptoms:

  • Headache
  • Dizziness
  • Nausea
  • Vomiting
  • Loss of appetite
  • Fever
  • Muscle aches, especially in knees and back
  • light sensitivity
  • Red tongue, eyes or face

In some cases, these symptoms improve within a few days. If the infection persists then, the person enters the toxic phase which can be fatal.

Toxic phase

In some cases, the symptoms of acute yellow fever persist and then, toxic phase starts. During the fatal toxic phase, symptoms of acute and initial phase reappear and become more-severe and life-threatening. These life threating symptoms are the following:

  • Jaundice (yellowing of the skin and the whites of eyes)
  • Abdominal pain
  • Vomiting, sometimes of blood
  • Decrease in urination
  • Internal bleeding (hemorrhaging)
  • Bleeding from nose, eyes or mouth
  • Bradycardia (Slow heartbeat)
  • Hepatitis (inflammation of the liver)
  • Kidney and liver failure
  • Multisystem organ failure leading to death
  • Brain dysfunction, like seizures, delirium, and coma

This toxic phase of yellow fever can be life-threating.

Causes of Yellow Fever 

Yellow fever is caused by a virus which is transmitted by the mosquito named “Aedes aegypti”. These mosquitoes can be found in human habitations, where they can live in even the cleanest water. These are also found in the jungle where they infect monkeys. Both human and monkeys are the host of this virus. Most cases of yellow fever viral infection are found in tropical South America and sub-Saharan Africa.

“Aedes aegypti” mosquitoes transmit the virus back and forth between humans and monkeys, or in both.

When an “Aedes aegypti” mosquito bites a monkey or a human infected with yellow fever, then the yellow fever virus enters the mosquito’s bloodstream. In this way, the yellow fever virus circulates in the bloodstream of mosquito and then, settles in its salivary glands.

When the infected mosquito bites a human or monkey, then the virus enters the host’s bloodstream, where it causes infection and illness.


No cure is available for yellow fever but the following two ways are effective for the prevention of disease:

1- Vaccinations 

No cure is available for yellow fever therefore only vaccination can be effective for this disease. Yellow fever is usually prevalent in the areas of South America and sub-Saharan Africa. If a person lives in any of these areas, then, he/she should get the yellow fever vaccination. If a person plans to travel in these areas then, he/she must get a vaccination of the yellow fever virus.

Yellow fever vaccine is highly effective, and a single dose of this vaccine provides protection for at least 10 years. Few side effects are associated with the vaccine which is usually mild and lasts for five to 10 days. The side effects are the following:

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

In rare cases, infants and older adults can have adverse side effects of vaccination, such as developing an infection like yellow fever and encephalitis (inflammation of the brain). The vaccine is considered safe for people among the ages of 9 months and 60 years.

The people with a weakened immune system (immunocompromised) should consult a doctor before talking vaccination to avoid complications.

2- Mosquito protection

Yellow fever virus spreads via mosquitoes, therefore one can prevent the disease by protecting yourself against mosquitos. One can take measure to control the exposure to mosquitos, some of which are the following:

  • Wear fully covered dresses (long-sleeved shirts and long pants) when you go into mosquito-infested areas
  • Avoid unnecessary outdoor activities
  • Live in well-screened or air-conditioned housing
  • Bed nets can also be used to prevent mosquitos. The bed nets that are pre-treated with insecticide offer additional protection against mosquitos.
  • Nonskin repellent can also be used. For this purpose, permethrin-containing mosquito repellent can be applied to shoes, clothing, bed netting, and camping gear. The clothing and gear pre-treated with permethrin are also available which can be bought. Permethrin is not for use on skin.
  • Skin repellent is also effective. The Products with the active ingredients picaridin or DEET IR3535 are skin repellents. These repellents provide long-lasting skin protection against mosquitos. The concentration of repellent to be used depends upon the hours of protection required. Higher concentrations provide last longer effects.

Note: The use of chemical repellents can be toxic, therefore one should be careful while using it. DEET should not be used on the hands of infants or young children to avoid the risk of toxicities.

Final words

Yellow fever virus can cause a deadly infection. No cure is available for yellow fever, but prevention measures should be taken. Therefore, the people living in mosquitos infested areas should get vaccination on time to prevent the risk of illness.



Hilary Jensen

Hilary is a Food Science and Nutrition graduate with specialization in diet planning and weight loss. She enjoys reading and writing on Food, Nutrition, Diet, Weight Loss, and General Health.

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