Introduction

Yellow fever is a viral illness that is spread by mosquito bites, predominantly found in tropical and subtropical areas of South America, Central America, and Africa. The primary vectors are Aedes and Haemagogus mosquitoes that bite during the day. When you are infected with yellow fever, there is a wide range of symptoms that manifest. It can be a mild fever to a severe haemorrhage or liver disease.¹

After being bitten by an infected mosquito, the symptoms typically appear within 3-6 days or longer. The symptoms will be similar to getting the flu, such as a fever, headache, body aches, loss of appetite, and feeling unwell or sick, which can last up to 3-4 days.

However, there are also severe symptoms that may manifest, such as jaundice (yellowing of your skin and eyes), dark-coloured urine, stomach pain, and bleeding from the stomach or eyes, nose, and mouth.² If these symptoms present, it is likely to have impacted more than one organ of the body, usually the liver and kidneys.³ Due to these possible fatalities, it is crucial to take measures before you put yourself at risk of being infected, especially if you are living in these high-risk areas or are planning to travel there. 

How to prevent yellow fever

Vaccination

Vaccination is the most vital preventative measure against yellow fever.³ The vaccine known as YF 17D is a safe, inexpensive, and effective vaccine that has been used for more than half a century to prevent yellow fever. In some countries, it has been implemented as a routine vaccination, but this is not yet the case in others. 

A yellow fever vaccination certificate is valid from 10 days after being vaccinated and lasts for your whole life. Generally, you don’t need a booster dose of the yellow fever vaccine as it provides you with lifelong protection.⁴ However, if you are someone who is travelling to areas with ongoing outbreaks and it has been 10 years or more since your last vaccination, you may consider getting a booster shot.^5,6

Yellow fever vaccination is recommended for anyone 9 months old and older. Some groups of people are at higher risk of developing a reaction to the yellow fever vaccine but still may be considered for its benefit. These people include:⁵

• Babies between six and eight months old
• Individuals over 60 years old
• Pregnant and breastfeeding birth parents 

A vaccine is not recommended for people with some conditions:⁵

• Vaccine allergy
• Babies that are six months old or younger 
• Organ transplant recipients
• People diagnosed with a malignant tumour or cancer
• Anyone with thymus disorder (associated with abnormal immune function)
• Primary immunodeficiencies (chronic conditions where part of the immune system is missing or does not function correctly)
• Those using immunosuppressive and immunomodulatory therapies 
• Diagnosed and showed symptoms of HIV/AIDS

After receiving a yellow fever vaccine, you normally only feel mild reactions, such as headaches, body aches, and low-grade fever. However, in rare conditions, people may experience a severe reaction and sometimes a life-threatening one. These include:⁷

• Anaphylaxis reactions, such as difficulty breathing and swallowing
• Swelling of the brain and surrounding tissues
• Internal organ failure or dysfunction
• Gullain-Barré syndrome (a condition affecting the nervous system in which a person’s immune system damages the nerve cells, causing muscle weakness or even paralysis)

It is crucial to communicate with your healthcare provider before being administered any vaccinations so they can assess your eligibility. If you are experiencing any of these severe reactions post-vaccination, please seek medical attention immediately.⁷

Mosquito bite prevention

Vector control

A mosquito is a vector, which is defined as an organism that transmits infectious disease from organism to organism. While vaccination is a crucial measure in preventing yellow fever, vector control also plays an important role, since this disease is transmitted by mosquitoes. In urban areas, the transmission can be reduced by eliminating potential mosquito breeding sites. Applying larvicides to kill the larvae in water storage containers, tyres, and other potential areas where standing water accumulates proves to be beneficial. Larvaciding can also be carried out by biological larvacides, such as bacteria and toxins, to kill the larvae before they become adults. Additionally, modifying the environment to make it less hospitable to mosquitoes can be achieved by improving the drainage and planting repellent plants.^3,8

Personal protection

Here is how you can shield yourself from mosquito bites and prevent yellow fever transmission:

• Wear long-sleeved clothing, which will minimise skin exposure to mosquitoes and choose fabrics in neutral colours, as mosquitoes are attracted to darker colours 
• Apply mosquito repellents to your skin
• Use bed nets that will provide a physical barrier while sleeping. Unfortunately, the effectiveness of using insecticide-treated bed nets is limited by the fact that Aedes mosquitoes bite during the daytime

Additional measure

Raising community awareness about yellow fever symptoms and encouraging them to seek medical attention immediately if they suspect yellow fever will contribute to the early detection of this disease. Prompt detection and rapid response through vaccination are also essential in controlling outbreaks. 

A recommendation from the World Health Organisation (WHO) states that every at-risk country should have at least one national laboratory to perform basic yellow fever blood tests. If a case of yellow fever in an unvaccinated population is confirmed, it will be considered an outbreak. This state triggers an immediate investigation that should include emergency measures and long-term immunisation plans. 

FAQs

What are the preventive measures for yellow fever?

• Yellow fever vaccination
• Travel precautions to high-risk regions
• Vector control (eliminating breeding sites of the mosquitoes) and the use of larvacides to kill the larvae before they become adults
• Use insect repellent, wear long-sleeved shirts and pants
• Early detection of the disease and outbreak preparedness

What is the single most important measure for preventing yellow fever?

Vaccination. The prevention can only be achieved if the majority of the population is vaccinated. It is highly effective and offers up to 99% protection for most people from yellow fever. Generally, it will give you lifelong immunity against it. The vaccine is also widely available, safe, and relatively affordable, especially in higher-risk regions. 

What was the strategy to get rid of yellow fever?

A comprehensive and long-term strategy called The EYE (Eliminate Yellow Fever Epidemics) strategy aims to end yellow fever epidemics by 2026 and consists of three strategic objectives:

1. Protect at-risk populations to ensure the coverage of the vaccination, so every individual at high risk is protected against the disease
2. Preventing international spread by safeguarding high-risk workers, enhancing compliance with International Health Regulations (IHR) through attentive verification of vaccination requirements at entry points, and facilitating the development of readiness plans to mitigate the risk of yellow fever outbreaks
3. Contain outbreaks rapidly, as it is essential to prevent amplification into more devastating outbreaks⁹

Is there a preventative vaccine for yellow fever?

Yes, it is called the YF 17D vaccine, which creates lifelong immunity for yellow fever.

What precautions should be taken during the yellow fever vaccine?

• Inform your healthcare provider about any pre-existing medical condition, such as an allergy (including egg allergy), or any immunocompromised condition, such as cancer, HIV, or thymus disease. Don’t forget to mention if you are currently pregnant or breastfeeding, as they will consider whether it is safer for you to be vaccinated or not
• Know the potential reaction of side effects that may arise after the vaccination. You can ask the person in charge of your vaccination about this. The common reaction will be a headache, low-grade fever, muscle aches, and pain at the site of injection. However, be aware of other severe reactions that may occur, although it is relatively rare

Why is it named “yellow fever”?

 The “yellow” in the name refers to the effects of jaundice that may affect some infected persons. Jaundice is a condition that makes the skin and the white part of your eyes turn yellow due to the build-up of bilirubin, a waste product from the breakdown of red blood cells. In severe cases, yellow fever infection can cause damage to the liver that leads to impaired bilirubin processing and causes this yellowing.¹⁰

Summary

Yellow fever is a viral infection transmitted by mosquitoes that is primarily found in South America, Central America, and Africa. This infection typically manifests with flu-like symptoms; however, in severe cases, it can damage the liver and kidneys. Hence, preventing the infection is crucial. Preventative measures include:

• Vaccination, mainly for people living in high-risk regions and those who are planning to travel there
• Vector control by eliminating potential mosquito breeding sites and applying larvacide
• Personal protection, including wearing long-sleeve shirts and pants and applying mosquito repellent to the skin
• Raising public awareness of yellow fever through education
• Prompt surveillance and response system to detect and contain outbreaks