Yellow Fever

What is yellow fever?

Yellow fever is a serious illness caused by a virus of the Flaviviridae family. The virus spreads between infected mosquitoes, and humans or certain species of monkey (hosts). Yellow fever is predominantly prevalent in certain parts of sub-Saharan Africa and tropical areas of South America.1

Most cases of YF only involve a mild infection characterised by flu-like illness, fever and nausea, but some individuals can get severe symptoms such as fever, jaundice (yellowing of the skin and eyes), bleeding from the nose, eyes and stomach and major organ (e.g. liver, kidneys and heart) failure may occur.  About half of infections that enter the second phase result in death.

An estimated 84000–170000 case and 29000-60000 deaths occur per year caused by yellow fever.2 There is no specific medicine to treat yellow fever.3 Serious cases require hospital admission.

The following is a summary about the disease. For further details speak to your local pharmacist or GP.

How is Yellow fever spread?

Yellow fever is spread to humans via the bite from an infected female mosquito. These usually bite during the day, between dawn and dusk.

Once the virus enters the bloodstream, it targets the internal organs. The virus is then able to replicate and cause damage to these systems. The first organ to be affected is the liver; this usually occurs 24 hours after the virus enters the bloodstream.

The disease is more common in rural areas. Outbreaks in urban areas occur when infected people introduce the virus into densely populated areas and the mosquito vector is present to spread the virus from human to human.

The groups most at-risk of developing yellow fever include:

  • Travellers and individuals living in high density areas exposed to yellow fever
  • Workers in areas where yellow fever is prevalent (eg: forest worker, oil field workers)
  • Infants and the elderly

In which countries is yellow fever found?

Yellow fever is typically found in:

There is no risk of transmission in the UK.3

Further details of countries with risk of yellow fever can be found here.6

Note: Jan 2017 an upsurge of yellow fever activity in Brazil has expanded beyond those areas illustrated by the WHO Americas (2013) map. For an updated risk map please click here.7

What are the signs and symptoms of yellow fever?

The incubation period of yellow fever is 3-6 days typically but can be longer.

Phase 1 (Acute Phase):

The initial symptoms  lasts 3-4 days and may include:

  • Fever
  • Muscle ache, especially back pain
  • Headache
  • Shivering
  • Photophobia (dislike to light)
  • Anorexia
  • Nausea and vomiting
  • Fever may be very high but the pulse is typically slow

Most people make a recovery within 3-4 days.1

What are the complications of yellow fever?

Within 24 hours, around 15% of infected people enter the toxic phase.

The virus begins to infect white blood cells and from there it can reach the liver. It may lead to shock and multiple organ failure.

Phase 2 (Toxic Phase):

In addition to fever, nausea and vomiting severe symptoms also occur:

  • Jaundice
  • Haemorrhage
  • Abdominal pain with vomiting
  • Dark urine
  • Bleeding from the mouth, nose, eyes or stomach
  • Blood in vomit and faeces
  • Kidney function deterioration

Approximately 50% of patients entering this phase will die in 7-10 days.

Infection results in lifelong immunity in those who recover.1


These include:

  • Liver and kidney failure
  • Inflammation of the heart muscle
  • Secondary bacterial infections
  • Pulmonary Oedema (build-up of excess fluid in lungs)
  • Internal bleeding
  • Inflammation of the brain

How is yellow fever diagnosed and treated?

Yellow fever is difficult to diagnose, especially during the early stages. It can be confused with severe malaria, viral haemorrhagic fever and other diseases, as well as poisoning.2

Diagnosis is clinical, with symptoms of fever, pain, nausea and vomiting occurring 6-10 days after leaving an affected area. Most cases are mild but should be confirmed by a doctor because of the risk of outbreak.

The diagnosis is initially based on the patient’s symptoms, location and dates of travel, and activities.

There is no specific antiviral treatment for yellow fever. Treatment is purely symptomatic and primarily involves treating the patient to reduce the risks of dehydration, liver and kidney failure, respiratory failure and fever.

Treatment is supportive:

  • Paracetamol or ibuprofen to lower temperature and relieve aches and pains
  • Oral rehydration fluid to prevent dehydration3

What advice is there for those travelling to high risk countries?

There are two methods to prevent Yellow fever:

  • Vaccination
  • Mosquito control with bite avoidance: using mosquito nets, mosquito repellents and long sleeved clothing are useful for prevention of bites1

When to consider vaccination?

Vaccination is recommended for all travellers visiting countries where there is a high risk of yellow fever virus transmission.

Travellers without the benefit of vaccination are advised of the risk of contracting yellow fever and the potential for quarantine at the port of entry, depending on the country requirements for vaccination. A full summary of countries that require proof of yellow fever vaccinations can be found here.8

Countries with risk of Yellow fever transmission may or may not require proof of Yellow fever vaccination from travellers. The absence of a requirement for Yellow fever vaccination does not mean that there is no risk of Yellow fever in the country, and Yellow fever immunisation may still be recommended for the protection of the individual traveller.1


Yellow fever vaccine is available for adults and children aged 9 months or older.

The vaccine is a live attenuated form of the virus administered as a single dose. Protection begins by the tenth day after vaccination. It should therefore be given at least 10 days prior to travel to the high risk area, to allow sufficient immunity to develop. Once given the vaccine lasts for life.

It can be administered at the same time as other live or inactivated vaccines. However, it is recommended that yellow fever and MMR vaccines should be given 28 days apart to ensure optimal antibody responses against both diseases.9

Yellow fever vaccination is not available on the NHS and is given by registered Yellow fever Centres.3


This information is taken from trusted third party websites, NaTHNaC (Travel Health Pro) and EMIS (Patient info) and use of all information has been licenced under the Open Government Licence

Although the materials are being used/replicated under the provisions of the Open Government Licence this in no way represents endorsement of by NaTHNaC, Emis, Public Health England, the NHS or the Department of Health and Social Care.

  1. Travel Health Pro: Yellow fever
  2. World Health Organisation (WHO): Yellow fever
  3. NHS: Yellow fever
  4. WHO maps: Yellow fever vaccination recommendations in Africa, 2015
  5. WHO maps: Yellow fever vaccination recommendations in Americas, 2013
  6. Yellow Fever Zone: Yellow fever maps
  7. European centre for disease prevention and control: Yellow fever distribution in Brazil: Map
  8. WHO: List of countries, territories and areas – yellow fever vaccination requirements and recommendations; malaria situation; and other vaccination requirements
  9. The Green Book: Chapter 35 – Yellow fever