In today’s world of frequent travel and increasingly intertwined urban, rural, and forest environments, yellow fever remains a significant global health threat. Far more than a passing fever, yellow fever is an acute viral hemorrhagic disease that can lead to severe and often fatal complications if not detected and treated early.
How Yellow Fever Spreads
Yellow fever is caused by a virus transmitted primarily through the bite of infected Aedes aegypti mosquitoes. These mosquitoes are particularly dangerous because they are active during daylight hours, especially in the early morning and late afternoon. Their ability to breed near human dwellings—inside homes, around stagnant water sources, or in humid forested areas—makes it easier for the disease to spread in both urban and rural settings.
The disease is endemic in large parts of West, Central, and East Africa, as well as in Central and South America. Importantly, yellow fever does not spread directly from person to person. Instead, an infected mosquito bites a person carrying the virus and later transmits it to another healthy individual, continuing the cycle of infection. Once infected, the mosquito remains a lifelong carrier of the virus.
Incubation Period and Symptoms
The incubation period—the time between the mosquito bite and the appearance of symptoms—typically ranges from 3 to 6 days. Interestingly, many infected individuals may remain asymptomatic, a phenomenon known as “silent infection.” Despite the absence of symptoms, these individuals can still contribute to disease transmission if bitten by mosquitoes.
When symptoms do occur, they often appear suddenly and may include:
Fever
Severe headache
Muscle and joint pain
Loss of appetite
Red eyes
Nausea or vomiting
In most cases, these symptoms improve within 3–4 days, and patients may seem to have recovered completely. However, a dangerous turning point can follow: some patients relapse within 24 hours into a more severe phase. During this stage, the virus causes serious damage to internal organs, particularly the liver and kidneys, leading to jaundice—a yellowing of the skin and eyes from which the disease gets its name. Patients may also experience dark urine, abdominal pain with vomiting, and bleeding from the mouth, nose, eyes, or stomach. Alarmingly, statistics show that about half of those who enter this critical phase may die within 7 to 10 days.
Diagnosis and Treatment
Currently, there is no specific antiviral treatment for yellow fever. Medical care focuses on alleviating symptoms and supporting the body’s vital functions during the acute phase. Diagnosis typically involves laboratory tests to detect the virus or its antibodies in the blood, combined with a patient’s clinical symptoms and recent travel history to affected areas.
Supportive care may include:
Complete rest
Adequate hydration to prevent dehydration
Pain relievers and fever reducers (excluding aspirin and non-steroidal anti-inflammatory drugs due to increased bleeding risk)
Antibiotics, if there are secondary bacterial infections
Continuous monitoring of liver and kidney function
Hospitalisation for patients with severe symptoms provides intensive medical care
Prevention: The First Line of Defence
Preventing yellow fever relies on two main strategies: vaccination and mosquito control.
Vaccination
Vaccination is the most effective measure against yellow fever. A single dose of the yellow fever vaccine provides lifelong immunity. Travellers are advised to receive the vaccine at least 10 days before visiting endemic areas. However, certain groups should avoid vaccination, including:
Infants under nine months
Pregnant women (unless during a major outbreak)
Individuals with severe allergies to eggs
People with severe immunodeficiency
Some countries require proof of vaccination for travellers coming from or travelling to endemic regions.
Mosquito Control
Controlling mosquito populations remains equally crucial and includes:
Eliminating breeding sites like stagnant water, open water containers, and ponds
Using insecticides and repellents, as well as sleeping under mosquito nets
Wearing long-sleeved clothing and socks to reduce skin exposure to mosquito bites
Conclusion
While yellow fever is undeniably a serious and potentially deadly disease, it is largely preventable. Vaccination, effective mosquito control, and raising public awareness are essential to reducing its spread. Protecting ourselves and our communities begins with simple, proactive measures—because when it comes to yellow fever, prevention truly is better than a cure.
By: Dr Badreyya Al-Harmi, Consultant Public Health
