All About Yellow Fever

Yellow fever, caused by the yellow fever virus (YFV) from the Flaviviridae family, primarily spreads through the bites of Aedes or Haemagogus mosquitoes prevalent in tropical and subtropical regions of Africa and South America. When a mosquito bites an infected person or animal, it can become infected with the yellow fever virus. The mosquito can then transmit the virus to other individuals it bites. Direct transmission from person to person is rare, although it can occur through contact with infected blood, such as during blood transfusions or from mother to baby during childbirth. While yellow fever symptoms can range from mild flu-like illness to severe and potentially fatal complications, vaccination offers a powerful shield against this potentially devastating disease.

The Spectrum of Symptoms

Yellow fever manifests in two distinct phases:

• Acute Phase (3-6 days after infection): 

This initial phase presents with flu-like symptoms such as fever, headache, muscle pain, nausea, vomiting, and fatigue. These can be easily confused with other common tropical illnesses like dengue or malaria.

• Toxic Phase (15% of cases): 

Within 24 hours of apparent recovery, a more severe toxic phase may develop. Symptoms include high fever, jaundice which is the yellowing of the skin and eyes, abdominal pain, bloody vomiting, and organ dysfunction of the liver and kidneys. Untreated severe cases can lead to bleeding disorders, shock, organ failure, and a mortality rate as high as 50%.

Long-term Effects & Mortality of Yellow Fever
The long term effects of yellow fever can vary depending on the severity of the infection and the individual’s overall health. In most cases, individuals who recover from yellow fever do not experience long-term complications. However, in severe cases, yellow fever can cause organ damage, particularly to the liver and kidneys, which may lead to long-term health problems.

The fatality rate for yellow fever is estimated to be between 5% and 10%. However, in severe outbreaks, particularly in areas with limited healthcare resources, the mortality rate can be much higher, reaching up to 50% or more among those with severe cases.

Yellow Fever Countries & Prevention
Yellow fever is primarily found in tropical and subtropical regions of Africa and South America, where the Aedes aegypti mosquito, the primary vector of the yellow fever virus, thrives. In Africa, yellow fever is endemic in parts of West and Central Africa, including countries such as Nigeria, Democratic Republic of the Congo, and Angola. In South America, endemic regions include parts of Brazil, Peru, and Colombia.

The yellow fever vaccine provides long-lasting immunity for most people. A single dose of the vaccine is typically considered sufficient to provide protection against yellow fever for at least 10 years, and often for a lifetime. Booster doses may be necessary for individuals at continued risk of exposure. It is recommended for everyone aged 9 months and older travelling to or residing in yellow fever-endemic areas.

The Singaporean Ministry of Health (MOH) oversees the availability and administration of the yellow fever vaccine. Travellers planning trips to high-risk regions should consult healthcare providers or travel medicine specialists well in advance. This ensures they receive the vaccine and obtain the International Certificate of Vaccination or Prophylaxis (ICVP), also known as the “yellow card,” a mandatory travel document for many yellow fever-endemic countries.

Understanding Potential Side Effects
While generally safe, the yellow fever vaccine can cause mild to moderate side effects in some individuals:

• Common Side Effects: These include low-grade fever, headache, muscle aches, and soreness at the injection site. These typically resolve on their own within a few days.
• Rare Side Effects: Serious allergic reactions such as anaphylaxis and neurological complications like Guillain-Barré Syndrome (GBS) are extremely rare but possible. They require immediate medical attention.

Beyond Vaccination: Protective Measures Against Mosquito Bites
In addition to vaccination, travellers can significantly reduce their risk of contracting yellow fever by taking precautions to prevent mosquito bites:

• Insect Repellents: Use insect repellents containing DEET, picaridin, or oil of lemon eucalyptus, following application instructions carefully.
• Protective Clothing: Wear long-sleeved shirts, long pants, and hats, especially during peak mosquito biting times which are during dawn and dusk.
• Accommodation: Choose accommodations with screened windows or air conditioning to minimise mosquito exposure.
• Travel Advisories: Stay informed about current yellow fever outbreaks and travel advisories for your destination by consulting the MOH website or reputable travel health resources.

Finding a Yellow Fever Vaccination Clinic in Singapore
A simple online search for “yellow fever vaccination Singapore” or contacting the MOH can help you locate healthcare providers or travel clinics authorised to administer the yellow fever vaccine.

Yellow fever poses a serious threat in endemic regions, but with proper knowledge and preparation, travellers can significantly reduce their risk of contracting the disease. By understanding the symptoms, getting vaccinated well before departure, and practising effective mosquito bite prevention strategies, Singaporean travellers can embark on their adventures with peace of mind, enjoying their journeys while safeguarding their health.

Book your yellow fever vaccine with Minmed today!