Question:
Doctor,
Recently the media highlighted a death from Yellow fever. We are scared. Are we at risk of getting this disease? What is it? A new disease? How come we haven’t been hearing about it a lot? Is it an epidemic? Why did the person highlighted in the media die? Isn’t there any treatment for this disease? What can we do to avoid it? Please shed light on this matter. We are scared….Sincerely, Concerned Staff
Answer:
Dear Concerned Staff,
Thank you for asking. Yellow fever has been with us for a long time. The recent case highlighted the need to maintain surveillance. Apparently the man had been infected in Angola and made it back home to Kenya with the disease. Unfortunately, he succumbed while receiving treatment in Kenyatta National Referral Hospital. At least the media publicity of this unfortunate patient gives us cause to remind ourselves about this condition.
Transmission
Yellow fever is a serious viral disease transmitted by infected mosquitoes, of the Aedes type in Kenya. A typical one is shown below. The mosquito is the primary vector. It carries the virus from one host to another, primarily between monkeys, from monkeys to humans, and from humans to humans.
This yellow fever virus is common in tropical areas of Africa, including Kenya. See the map below:

As can be seen above, the eastern borders of Kenya (next to Somalia) and southern borders (next to Tanzania) have very high risk.
Summary Facts
A person with Yellow fever turns “yellow”. The “yellow” in the name refers to the yellowness of the eyes (what we call jaundice) that affects some patients. Up to 50% of severely affected persons without treatment will die from yellow fever. There is no specific treatment for yellow fever. Treatment is symptomatic, aimed at reducing the symptoms for the comfort of the patient. Vaccination is the most important preventive measure against yellow fever. The vaccine is safe, affordable, and highly effective. A single dose of yellow fever vaccine is sufficient to confer sustained immunity and life-long protection against yellow fever disease and a booster dose of yellow fever vaccine is usually not needed. However, we ask a person to get a vaccine every 10 years just to be sure there is optimal protection. The vaccine provides effective immunity within 30 days for 99% of persons vaccinated.
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Signs and symptoms
Once contracted, the yellow fever virus incubates in the body for 3 to 6 days, followed by infection that can occur in one or two phases. The first, “acute”, phase usually causes fever, muscle pain with prominent backache, headache, shivers, loss of appetite, and nausea or vomiting. Most patients improve and their symptoms disappear after 3 to 4 days.

However, 15% of patients enter a second, more toxic phase within 24 hours of the initial remission. High fever returns and several body systems are affected. The patient rapidly develops jaundice and complains of abdominal pain with vomiting. Bleeding can occur from the mouth, nose, eyes or stomach. Once this happens, blood appears in the vomit and faeces. Kidney function deteriorates. Half of the patients who enter the toxic phase die within 10 to 14 days, the rest recover without significant organ damage.
Yellow fever is difficult to diagnose, especially during the early stages. It can be confused with severe malaria, dengue fever, hepatitis and other diseases. Blood tests can detect yellow fever.
Treatment
There is no specific treatment for yellow fever, only supportive care to treat dehydration, respiratory failure, and fever. Associated bacterial infections can be treated with antibiotics. Supportive care may improve outcomes for seriously ill patients.
Prevention
1. Vaccination
Vaccination is the single most important measure for preventing yellow fever. To prevent outbreaks throughout affected regions, vaccination coverage must reach at least 60% to 80% of a population at risk. Preventive vaccination can be offered through routine infant immunization and one-time mass campaigns to increase vaccination coverage in countries at risk, as well as for travelers to yellow fever endemic area. WHO strongly recommends routine yellow fever vaccination for children in areas at risk for the disease. I strongly recommend that everyone gets this Yellow Fever vaccine. Serious side effects are extremely rare. Vaccination for persons over 60 years of age should be administrated after a careful risk-benefit assessment, comparing the risk of acquiring yellow fever versus the risk of a potential serious adverse event following immunization.
The risk of death from yellow fever disease is far greater than the risks related to the vaccine. People who should not be vaccinated include:
• Infants aged less than 9 months (with the exception that infants aged 6-9 months should be vaccinated during an epidemic where the risk of disease is higher than the risk of an adverse effect of the vaccine);
• Pregnant women – except during a yellow fever outbreak when the risk of infection is high;
• People with severe allergies to egg protein; and
• People with severe immunodeficiency due to symptomatic HIV/AIDS or other causes
• Travellers from a place with an epidemic (e.g. Angola) who have medical grounds for not getting vaccinated, International Health Regulations state that this must be certified by the appropriate authorities.
2. Mosquito control
The risk of yellow fever transmission in urban areas can be reduced by eliminating potential mosquito breeding sites and applying insecticides to water where they develop in their earliest stages. Application of spray insecticides to kill adult mosquitoes during urban epidemics, combined with emergency vaccination campaigns, can reduce or halt yellow fever transmission, “buying time” for vaccinated populations to build immunity.
3. Epidemic preparedness and response
Prompt detection of yellow fever and rapid response through emergency vaccination campaigns are essential for controlling outbreaks.
Addendum
The rains are around the corner. This will be a mosquito breeding season. Ensure pools of water around where you live are drained. And above all things ensure you are vaccinated. You can get this done in any hospital, the City County hall or any of the airport health services.