Yellow Fever

About yellow fever
Yellow fever (YF) is an acute viral haemorrhagic disease transmitted by infected mosquitoes. It is endemic in tropical areas of Africa (34 countries) and Latin America (13 countries). Vaccination is the most important and effective measure against YF providing effective immunity within 30 days for 99% of those vaccinated.

The disease is spread by mosquitoes that bite mostly during the day. Yellow fever can cause a serious haemorrhagic Illness that can be fatal for humans. The “yellow” in the name refers to the jaundice that affects some patients. Travellers to areas considered “at risk” can help limit the spread of the disease to vulnerable local populations by ensuring they are vaccinated where recommended.

The incubation period between being bitten by a mosquito to developing infection is 3-6 days. Symptoms including fever, headache, myalgia, conjunctival infection, facial flushing and relative bradycardia (slow heart rate) are common. In severe cases, these symptoms remit for a few hours to days then recur with high fever, headache, lumbosacral pain, nausea, vomiting, abdominal pain, impaired level of consciousness, severe hepatitis, shock and multisite haemorrhage. In many patients, there will be improvement in symptoms and gradual recovery 3-4 days after the onset of symptoms. About 15% of people infected with yellow fever develop a more severe form of the illness, and of those, up to half will die.

Survival rates are improved with supportive hospital care, however, there is no specific cure for YF. The New Zealand Health, Te Whatu Ora website provides further information on the YF virus and other relevant information about vaccination.

Recent outbreaks
Countries which have suffered recent outbreaks of YF include Trinidad in the Caribbean, Burkina Faso, Cameroon, Central African Republic, Chad, Republic of the Congo, Cote d’Ivoire, Democratic Republic of the Congo, Guinea, Niger, Nigeria, South Sudan, Togo, and Uganda.

In South America, from January to March 2024, 7 confirmed yellow fever cases, including 4 fatal cases, have been reported in Columbia (3 fatal cases), Guyana (2 cases), and Peru (2 cases including one death). Additionally, Brazil has reported confirmed yellow fever in monkeys which indicates it is circulating in the country.

The mosquitoes that can spread this virus are not found in New Zealand. New Zealand is free from yellow fever virus.

Yellow fever vaccine
Yellow fever is prevented by a vaccine. A single dose of YF vaccine is sufficient to grant life-long protection. The World Health Organization (WHO) advises YF vaccine for all travellers aged 9 months and older visiting countries with areas with a risk of YF.

Travellers who are planning to travel to countries in Africa or South America where YF is endemic should receive vaccination. Yellow fever vaccination is only available from authorised YF vaccinator from these designated vaccination centres.

Travellers to countries where mosquito borne illnesses can spread are advised to use insect repellent, wear protective clothing, and stay in lodgings where there are mosquito screens on windows and doors. Because yellow fever virus is transmitted by mosquitoes mostly active during daytime, it is important that all travellers visiting affected areas continue to take protective measures to prevent mosquito bites throughout the day. The Mosquitoes – Health New Zealand | Te Whatu Ora website contains more advice on avoiding mosquito bites while travelling, including information about mosquitoes.

If you feel unwell during your trip or in the first three weeks after your return, you are advised to seek immediate medical advice and tell the doctor about your travel.

 

 

Reviewed:22 May 2024, 14:20