Quick facts about yellow fever

Thursday, March 10th, 2022 04:00 | By
Image is used for representation. PHOTO/Courtesy

The country has been on high alert after three people died of suspected yellow fever in Isiolo county. The Ministry of Health is currently managing the situation. Well, for  many Kenyans, they probably only hear of the disease while travelling to countries that require visitors to be vaccinated against it. Malemba Mkongo explores more about the viral infection

  1. It is transmitted by infected mosquitoes

Acting Director General of Health Patrick Amoth says yellow fever is an acute viral haemorrhagic disease transmitted by infected mosquitoes of the Aedes species. Yellow fever virus is transmitted through the bite of an infected mosquito. Once contacted, it incubates in the body for three to six days. The yellow fever causing mosquito thrives near human habitation and can breed even in the cleanest environment. The most commons species to be infected by the disease are human beings and monkeys.

2. It got it’s name from it’s most obvious symptoms

Yellow fever got its name from two of its most obvious symptoms: fever and yellowing of the skin (jaundice). The yellowing occurs because the disease causes liver damage and hepatitis.

3. Patients with severe symptoms die within 10 to 14 days

Symptoms of yellow fever infection include a sudden onset of fever, chills, muscle pain, backache, headache, nausea and vomiting. The signs start showcasing between three to six days after coming to contact with the virus, but disappear after three to four days. About 15 per cent of patients tend to get serious signs such as bleeding (from the mouth, nose and eyes and/or stomach), jaundice (yellowing of the skin and eyes), and abdominal pain with vomiting and problems with kidney function.  Half of these patients recover, but the remaining half die within 10 to 14 days of developing these symptoms.

4. It is difficult to diagnose

Yellow fever is difficult to diagnose, especially during the early stages since the first signs manifest as other dieseases such as malaria and typhoid. However, one’s travel history and activities to areas considered infectious prone among other issues can help in determining the possibility of yellow fever at an early stage. Blood tests (RT-PCR) can sometimes detect the virus in the early stages of the disease and testing to identify antibodies is needed to detect late stages. Laboratory diagnosis of yellow fever is generally accomplished by testing of serum to detect virus-specific. Tests may take up to four to 14 days after receipt of the samples before the results can be concluded.

5. There is no specific treatment for yellow fever

No specific treatments have been found to help patients with yellow fever. If possible, patients with yellow fever should be hospitalised for treatment of their symptoms and closely observed by healthcare workers. Rest, fluids, and use of pain killers and fever-reducing medications may relieve symptoms of fever and aching. Certain medications should be avoided, such as aspirin or other non-steroidal anti-inflammatory drugs (such as ibuprofen and naproxen), because these may increase the risk for bleeding.

6. Africa is a good breeding ground

Yellow fever is most common in Sub-Saharan Africa and tropical South America due to its tropical and semi-tropical nature, which gives the yellow fever spreading mosquito a good ground to breed. Thirty-four countries in Western and Eastern Africa including Kenya, Uganda, Rwanda, Burundi and South Sudan are at the highest risk for yellow fever epidemics. Africa is estimated to record between 84,000–170,000 severe cases and 29,000–60,000 deaths annually.

7. Vaccination is the most important measure

The yellow fever vaccine is advised for adults and children over age nine months who are traveling to or living in countries with a known risk. In high-risk areas where vaccination coverage is low, mass immunisation is encouraged to preventing epidemics and control outbreaks. The vaccine is safe and a single dose provides life-long protection against yellow fever disease. A booster dose of yellow fever vaccine is not needed. There have been rare reports of serious side-effects from the yellow fever vaccine. The rates for these severe ‘adverse events following immunisation, when the vaccine provokes an attack on the liver, the kidneys or on the nervous system, leading to hospitalisation, are between 400 and 800 people in every 100 000 people vaccinated. Kenyans can get the vaccine in public and private hospitals with costs ranging between Sh1,500 to Sh5,000. World Health Organisation (WHO) calls for affordability of the vaccines.

8. Proof of vaccination before entry may be needed

Majority countries not prone to yellow fever always demand for proof of vaccination before entry. This is done through the production of yellow card issued after someone is vaccinated, which lasts a life  time. While some countries have set vaccination areas within the airports where unvaccinated persons can acquire the vaccines, other countries deny unvaccinated people entry. This is because it is believed the vaccine takes effect after 10 days. According to Europe Center for Disease Prevention and Control (ECDC) recent years has seen a number of unvaccinated tourists from Europe and North America die of the disease after visiting zoned areas thus the sustained calls for vaccination.

9. One confirmed case is considered an outbreak

There are concerns that cases of yellow fever are underreported and the true number of cases is estimated to be 10 to 250 times what is being reported. As such, WHO recommends that every at-risk country should have at least one national laboratory where basic yellow fever blood tests can be performed? One laboratory-confirmed case of yellow fever in an unvaccinated population is considered an outbreak. A confirmed case must be fully investigated, particularly in an area where most of the population has been vaccinated. Investigation teams must assess and respond to the outbreak with both emergency measures and longer-term immunisation plans. Kenya highly depends on Kenya Medical Research Institute (KEMRI) for testing and confirmation of such cases.

10. Mosquito control helps reduce transmission

The risk of yellow fever transmission in urban areas can be reduced by eliminating potential mosquito breeding sites. This can be done by spraying insecticides around water storage containers and other places where standing water collects. People are also advised to sleep under treated nets and also use a skin and non-skin mosquito repellant to keep mosquitos at bay.

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