A single mosquito bite can do more than leave behind an itchy bump. It can trigger a life-threatening disease that has claimed countless lives for centuries. Every year thousands of people fall seriously ill from yellow fever, a disease that is both preventable and potentially fatal.

It begins with what seems like an ordinary mosquito bite. Days later, the fever sets in. For some, recovery comes quickly. But for others, the illness takes a dangerous turn, leading to jaundice, internal bleeding, and organ failure. Despite the availability of an effective vaccine, yellow fever continues to pose a serious threat in many parts of the world.

Causes and transmission

The disease is caused by the yellow fever virus, carried mainly by the Aedes aegypti mosquito in urban areas, and by other species like Haemagogus in forest regions where the virus circulates between monkeys and mosquitoes.

Transmission begins when a mosquito bites an infected person or monkey, picking up the virus from their blood. The virus needs about 9–12 days inside the mosquito to reach its salivary glands before it can be passed on. Once infected, a mosquito can transmit the virus for life. When it bites another person, the virus enters the bloodstream and spreads through the body, particularly targeting the liver.

Most importantly, yellow fever does not spread directly from person to person. An infected mosquito is always required.

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Symptoms

Most symptoms are mild or no symptoms at all. When symptoms do appear, they typically start 3–6 days after the bite and include:

• Fever
• Chills
• Headache
• Muscle and back pain
• Nausea
• Vomiting
• Loss of appetite
• Fatigue

About 15% of cases progress to a more severe toxic phase after a brief remission, bringing:

• High fever
• Jaundice
• Abdominal pain
• Bleeding (from the gums, nose, or in vomit/stool)
• Kidney and liver failure

This severe stage can be fatal in up to half of cases, making early recognition important.

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Precautions and prevention

There is no specific antiviral treatment for yellow fever, so prevention is the most effective defence.

• Vaccination
• Mosquito bite prevention
• Eliminate breeding sites
• Peak activity awareness

For residents in non-endemic regions like the UAE, the main risk comes from travel to affected countries, making pre-trip vaccination and mosquito precautions especially relevant.

Though yellow fever isn’t endemic to the UAE, global travel means it’s never entirely out of reach. Travellers heading to affected parts of Africa and South America should take it seriously, get vaccinated well ahead of departure, pack mosquito repellent, and stay alert to symptoms after returning. A little preparation goes a long way in turning a potentially life-threatening illness into a non-issue.