How is Yellow Fever transmitted?


Mosquito sucking blood from a person's skin

Yellow Fever is an RNA virus that is thought to have originated in East or Central Africa, with transmission of the disease from nonhuman primates to humans.  The Yellow Fever virus can cause serious harm to humans and in some cases, can prove fatal. Early symptoms of Yellow Fever include fever, muscle pain, headache, shivers, loss of appetite, nausea and vomiting.

The mosquito host

Mosquitoes carry and transmit the Yellow Fever virus. But, how do they become infected with the disease?

One common way that mosquitoes become hosts of the Yellow Fever virus is by feeding on an infected human, or non-human primate. Once a female* mosquito feeds on an infected human or nonhuman primate they become infective after 9–12 days of incubation. She remains infective for life, which is typically several months.

Mosquitoes can also become infected with the Yellow Fever virus through vertical transmission. Vertical transmission occurs when the female mosquito passes the virus on to her eggs, which develop into infected offspring.

*only female mosquitoes bite. Male mosquitoes feed off flower nectar.

Yellow fever transmission cycles

Yellow fever virus has three transmission cycles: jungle (sylvatic), intermediate (savannah), and urban:

The Jungle Cycle

The jungle (sylvatic) cycle involves transmission of the virus between non-human primates and mosquito species that reside within the forest canopy. The virus is transmitted by mosquitoes from monkeys to humans when humans are visiting or working in the jungle.

The Intermediate Cycle

The intermediate (savannah) cycle exists in Africa. This transmission cycle involves the virus being passed from mosquitoes to humans in jungle border area. With the intermediate cycle, the virus can be passed from primate to human, or from human to human via mosquitoes.

The Urban Cycle

The urban cycle is the transmission of Yellow Fever between humans and urban mosquitoes, most notably Aedes aegypti. The virus is usually brought to the urban setting by an infected human who most likely caught the infection while visiting a jungle area.

Can humans spread yellow fever?

In short, no. Humans can’t spread Yellow Fever to each other via casual physical contact. However, the infection can be transmitted directly into the blood through contaminated needles.

Protection from Yellow Fever

If you’re travelling, visiting or even just passing through an area which is at risk of Yellow Fever, then it’s imperative that you have the correct vaccinations against the virus. On top of being vaccinated against Yellow Fever, it’s also essential to ensure you have the proper vaccination certificate.

Nearly all affected countries require proof of Yellow Fever vaccination in the form of an International Certificate of Vaccination before they permit entry. Failure to provide a valid certificate can lead to you being quarantined, immunised or denied entry.

At London Travel Clinic, we provide the Yellow Fever vaccine and Yellow Fever Certificate as standard at all of our vaccination clinics. We can also re-issue your certificate if you lose your original.

You should be vaccinated against Yellow Fever if you are travelling to:

  • An area where yellow fever is found – such as
  • A country that requires you to have a certificate proving vaccination against yellow fever
  • You need to have the vaccination at least ten days before travel to become effective and validate the certificate
  • The vaccine and certificates are only available at registered yellow fever vaccination centres such at London Travel Clinic

Is there treatment for yellow fever?

There is no treatment for yellow fever; you can only receive treatment for your symptoms while your body attempts to fight off the infection. The only prevention is through vaccination.

How else can I protect myself?

Your nurse at London Travel Clinic will talk to you about ways to avoid mosquito bites. This mosquito is a daytime biting insect so covering up, using insect repellents such as 30-50% DEET on exposed skin areas will help to prevent the illness too.

Article last reviewed on 06/02/2019 by:

Denise Chalkley RN, RM, RHV, BSc, AMFTM RCPS (Glas)
Clinical & Operations Director for Travel Medicine

Denise is an associate member of the Faculty of Travel Medicine, and a freelance lecturer at the Royal College of Physicians and Surgeons in Glasgow for the Faculty of Travel Medicine. She also lectures at the University of Hertfordshire teaching immunisations, tuberculosis, sexual health and travel medicine.

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