Yellow fever is a serious viral disease transmitted through mosquito bites, primarily affecting tropical regions of Africa and South America. Caused by the yellow fever virus (YFV) from the Flaviviridae family, it can range from mild flu-like symptoms to severe illness and even death. Understanding yellow fever, particularly for travellers, is crucial to ensure proper precautions are taken.
Symptoms & Stages of Yellow FeverÂ
The initial infection of YFV has an incubation period of 3 to 6 days before symptoms appear. The disease progresses through distinct phases:
- Initial (Acute) Phase (3-4 days):
- Sudden onset of high fever
- Intense headaches
- Muscle aches, particularly in the back and knees
- Chills and feeling cold despite fever
- Loss of appetite
- Nausea and vomiting
- Remission Phase:
- In many cases, these initial symptoms subside, leading to a temporary period where the patient feels better.
- Toxic Phase (Severe Yellow Fever): (Develops in some patients)
- Jaundice (yellowing of skin and eyes due to liver damage)
- Abdominal pain and vomiting
- Kidney dysfunction (reduced urine output, fluid retention)
- Heart problems (arrhythmias, cardiovascular complications)
- Bleeding from mouth, nose, eyes, or stomach
- Brain dysfunction (delirium, seizures, coma in severe cases)
The toxic phase can be fatal in 20-50% of severe cases without prompt medical attention.
Causes and Transmission of Yellow Fever
The primary culprit behind yellow fever transmission is the bite of infected mosquitoes. The Aedes aegypti species, particularly prevalent in urban areas, along with Haemagogus and Sabethes mosquitoes in forested areas, are the main carriers. These mosquitoes become infected by feeding on infected primates or humans. Once infected, they can transmit the virus to other humans through subsequent bites.
Humans and non-human primates serve as the primary hosts for the virus. 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.
Treatment and Prevention of Yellow Fever
Currently, there is no specific antiviral treatment for yellow fever. Management focuses on symptom relief and supportive care, including hospitalisation for severe cases to monitor and address complications like liver and kidney failure, shock, and bleeding.
The highly effective yellow fever vaccine provides long-lasting immunity. It’s recommended for travellers visiting endemic areas and mandatory for entry into certain countries, including some neighbouring to Singapore.
Getting a Yellow Fever Vaccine in Singapore
Singapore itself is free from yellow fever. However, to prevent the disease’s introduction, the Ministry of Health (MOH) mandates that all travellers, including Singapore residents, arriving from countries with a risk of yellow fever transmission within the past six days must possess a valid yellow fever vaccination certificate.
You can get the yellow fever vaccine at designated Yellow Fever Vaccination Centres, including travel health clinics and general practitioner (GP) clinics. A doctor will assess your suitability for the vaccine before administering it.Â
How long does the yellow fever immunisation last after receiving the yellow fever vaccine?
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.
Yellow fever is a serious yet preventable disease. By understanding the symptoms, causes, and available preventive measures, particularly vaccination for travellers, we can significantly reduce the risk of infection and outbreaks. If you’re planning a trip to a yellow fever-endemic region, ensure you get vaccinated well in advance, at least 10 days before travel and consult a healthcare professional for any questions or concerns.
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