Yellow fever

Yellow fever is an acute viral haemorrhagic disease transmitted by infected mosquitoes. It derives its name from the jaundice (yellowing of the skin and eyes) that affects some patients. While many cases are mild or asymptomatic, severe infections can cause high fever, bleeding, organ failure, and death.

This disease is a major public health concern in tropical regions of Africa and South America. Despite the existence of a highly effective vaccine, yellow fever continues to cause outbreaks due to inadequate immunisation coverage and weak health infrastructure in endemic areas.

Understanding yellow fever is vital for global health awareness, especially as increased travel and climate change expand the range of mosquito habitats. This page offers a comprehensive guide to the disease, including causes, symptoms, prevention, and support for those affected.

Yellow fever is a viral infection caused by the yellow fever virus (YFV), which belongs to the Flavivirus genus. It is primarily spread through the bite of infected mosquitoes, particularly Aedes aegypti and Haemagogus species.

The virus is endemic in specific parts of Africa and South America, and there is no specific cure once the disease is contracted. However, it is preventable through vaccination. The disease ranges in severity from asymptomatic to fatal, and about 15% of those infected enter a more serious phase with a high risk of death.

Yellow fever is not transmissible from person to person directly, though infected individuals can act as a source for further mosquito transmission.

Worldwide Prevalence

According to the World Health Organization (WHO), yellow fever causes an estimated 200,000 infections and 30,000 deaths annually. Around 90% of cases occur in Africa. The disease is endemic in 47 countries: 34 in Africa and 13 in Central and South America. Several major outbreaks have occurred in recent decades, mostly in Africa, with some reaching urban populations due to the spread of Aedes mosquitoes.

Prevalence in India

Yellow fever is not endemic in India, and no local transmission has ever been reported. However, due to international travel, India maintains strict surveillance and vaccination requirements for travellers coming from yellow fever-endemic countries. The Indian government requires a valid yellow fever vaccination certificate for individuals arriving from affected countries to prevent the introduction of the virus.

Yellow fever does not have medically classified subtypes in terms of disease manifestation, but it can be understood through the epidemiological transmission cycles:

1. Sylvatic (Jungle) Yellow Fever
   
   • Occurs in wild monkeys and is transmitted by forest mosquitoes to humans who enter the jungle.
2. Intermediate Yellow Fever
   
   • Occurs in rural or semi-urban areas where mosquitoes infect both monkeys and humans, causing localised outbreaks.
3. Urban Yellow Fever
   
   • Involves transmission between humans via Aedes aegypti mosquitoes in densely populated areas.

Yellow fever is caused by the yellow fever virus (YFV), which enters the bloodstream through the bite of an infected mosquito. Once inside the body, the virus replicates and spreads to the liver, spleen, lymph nodes, and other organs, potentially leading to severe organ damage.

Key causes include:

• Bites from infected Aedes or Haemagogus mosquitoes.
• Lack of vaccination.
• Travel to or living in endemic areas.
• Climate conditions favourable to mosquito breeding.

The symptoms of yellow fever develop in stages:

Initial (Acute) Phase:

• Sudden onset of fever
• Muscle pain (especially in the back)
• Headache
• Nausea and vomiting
• Fatigue and weakness
• Loss of appetite

Most patients recover within 3–4 days. However, around 15% progress to the toxic phase.

Toxic Phase:

• High fever returns after a brief remission
• Jaundice (yellowing of skin and eyes)
• Abdominal pain
• Vomiting (possibly with blood)
• Kidney and liver dysfunction
• Bleeding from the nose, mouth, eyes, or stomach
• Shock, coma, or death

The case fatality rate in severe cases can be as high as 50%.
 

Diagnosing yellow fever can be challenging due to symptom overlap with diseases like malaria, dengue, and hepatitis. Diagnosis typically includes:

• Patient history: Recent travel to endemic areas.
• Serological tests: Detection of yellow fever-specific IgM antibodies.
• Polymerase Chain Reaction (PCR): Identifies viral RNA in blood samples.
• Virus isolation: From blood samples (in specialised laboratories).
• Liver function tests: To check for hepatic involvement.

Early diagnosis is crucialfor supportive care and controlling outbreaks.

There is no specific antiviral treatment for yellow fever. Management focuses on supportive care to alleviate symptoms and prevent complications.

Supportive Care:

• Hospitalisation for moderate to severe cases
• Intravenous fluids to prevent dehydration, Oxygen therapy for respiratory support
• Medications to manage fever and pain (paracetamol preferred)
• Monitoring and treatment of liver and kidney functions
• Patients should avoid aspirin and NSAIDs, which may increase the risk of bleeding. (Dolonex DT 20mg tablet)
• Recovery from mild cases usually occurs within a week, while severe cases require intensive medical attention.

There is no scientific evidence supporting alternative therapies as a cure for yellow fever. However, some natural remedies may offer symptomatic relief:

• Herbal teas: Ginger or peppermint tea for nausea.
• Turmeric milk: May offer anti-inflammatory effects.
• Neem or tulsi infusions: Used traditionally to boost immunity, but not substitutes for medical care.

These should only be used under medical supervision and never replace clinical treatment or vaccination
 

Several factors increase the risk of contracting yellow fever:

• Lack of vaccination
• Travelling to endemic regions
• Outdoor activity during peak mosquito hours
• Living in rural or forested areas
• Climate change: Increases mosquito breeding and disease transmission
• Poor public health infrastructure

Infants, the elderly, and immunocompromised individuals are more susceptible to severe forms.

Yellow fever can lead to life-threatening complications, especially if the disease progresses to the toxic phase:

• Liver failure
• Kidney failure
• Severe haemorrhage
• Septic shock
• Myocarditis (inflammation of the heart)
• Secondary bacterial infections
• Death

Survivors of severe yellow fever may take weeks or months to fully recover.

If diagnosed with yellow fever:

• Rest and avoid strenuous activity.
• Stay hydrated with fluids and electrolytes.
• Eat small, light meals.
• Monitor for signs of bleeding or jaundice.
• Avoid exposure to further mosquito bites.
• Follow medical advice and complete follow-up tests.

Emotional and psychological support is also important, especially in severe or prolonged cases.

1. "Yellow fever only affects Africans or South Americans."
   
   • False. Anyone can get infected if exposed in endemic areas.
2. "Once vaccinated, you need a booster shot every 10 years."
   
   • Not anymore. WHO states one dose offers lifelong immunity for most.
3. "Yellow fever is the same as jaundice."
   
   • Incorrect. Jaundice is a symptom; yellow fever is a specific viral disease.
4. "There is a cure for yellow fever."
   
   • No cure exists; treatment is supportive.
5. "It can spread from person to person."
   
   • Only via mosquito vectors, not direct human contact.

Seek medical attention immediately if:

• You have returned from or live in an endemic area and develop fever.
• You experience symptoms like jaundice, bleeding, or vomiting blood.
• You feel extremely weak or have abdominal pain.

Early diagnosis can save lives by allowing proper management and containment.

• Do I need the yellow fever vaccine before travelling?
• What are the side effects of the vaccine?
• How can I protect myself from mosquitoes?
• Are there specific symptoms I should watch out for after travel?
• What should I do if I develop symptoms while abroad?

Support can be both emotional and practical:

• Help with day-to-day tasks while they recover.
• Ensure they are hydrated and take medications as advised.
• Provide comfort and reduce stress.
• Encourage mosquito protection methods to prevent further spread.
• Be patient during recovery, especially if the illness was severe.

Yellow fever remains a significant global health concern, particularly in parts of Africa and South America. Though not present in India, its potential for spread via international travel and climate change warrants ongoing vigilance.

Vaccination is the cornerstone of prevention, supported by mosquito control and public awareness. With no specific cure, early diagnosis and supportive care are essential to reduce mortality. Empowering individuals and communities with knowledge can play a vital role in controlling the impact of yellow fever.