Yellow fever

What is it?

Yellow fever is an acute viral haemorrhagic disease transmitted by infected mosquitos (arbovirus).

What to look for?

The incubation period of yellow fever is 3-6 days. The initial signs and symptoms are generally non-specific and include fever, chills, myalgia, fatigue and nausea or vomiting. Symptoms usually resolve within 3-4 days.

Approximately 15-25% of cases will enter a second, more toxic phase, within 24 hours after recovering from initial symptoms. This presents with a return of high fevers, vomiting, epigastric pain, jaundice (in reference to the name “yellow fever”), multi-organ failure and haemorrhage. Bleeding can occur from the mouth, nose, eyes or stomach.

20-25% of severe cases will result in death within 7-10 days after the onset of this second toxic phase.

How is it transmitted?

It is transmitted to humans by the bites of infected mosquitoes. Monkeys are the primary reservoir for yellow fever. Although, in heavily populated urban areas with high mosquito density, infected mosquitos can transmit the virus from person to person.

Epidemiology

Yellow fever disease occurs in the tropical and subtropical regions of Africa, the Caribbean and Central/South America. Disease risk depends on the time of year, duration of travel and degree of mosquito exposure.

Prevention

Stamaril® is the yellow fever vaccine registered for use in Australia. A single dose provides life-long protection. Yellow fever immunisation is not routinely given on the National Immunisation Program (NIP) and is only be administered in Australia as a travel vaccine by accredited yellow fever vaccination centres.

Accredited yellow fever vaccination centres will provide vaccine recipients with an International Certificate of Vaccination or Prophylaxis as proof of vaccination. All travellers entering Australia who have been in a declared yellow fever infected country within 6 days of arrival to Australia must show proof of vaccination. If you are travelling to yellow fever infected countries, it is strongly recommended that you check the yellow fever entry requirements for all the countries you intend to enter, prior to travel.

Vaccine precautions and contraindications

Stamaril® is a live-attenuated vaccine and is contraindicated in those who are:

• Anaphylactic to a previous dose of Stamaril®
• Anaphylactic to a component of Stamaril®
• Allergic or anaphylactic to eggs^
• Immunocompromised individuals
• Infants < 9-months of age
• Have a history of thymus disorders
• Pregnant women^

^Consider referral to Specialist Immunisation Clinic for discussion

Precautions should be taken when considering immunisation of:

• Adults aged ≥60 years
• Breastfeeding women

Adverse events following immunisation (AEFI)

Yellow fever-vaccine associated neurotropic disease (YF-AND) is a rare but serious AEFI of yellow fever vaccination. It includes diagnoses such as meningoencephalitis, Guillain-Barré syndrome, acute disseminated encephalomyelitis and bulbar palsy.

Yellow fever vaccine associated viscerotropic disease (YF-AVD) is rare and occurs in 3-4 cases per million doses of vaccine. It is characterised by multi-organ system failure and mimics natural yellow fever disease. Risk factors include older age and patients with a history of thymus disease.

Any suspected AEFI should be reported to SAEFVIC online or by calling 1300 882 924 (option 1).

Resources

• DHHS: Yellow fever vaccination centres
• Australian Immunisation Handbook: Yellow fever
• Australian Government Department of Health: Yellow fever general fact sheet
• World Health Organization: Yellow fever