Yellow fever is a severe viral illness which is transmitted by mosquito bites in tropical areas of the world. At the present time, transmission of the yellow fever is limited to specific areas of Africa and South America. The majority of reported yellow fever cases occur during the wet season in areas where transmission occurs. Clinical yellow fever illness is devastating and cases are frequently fatal. There is currently no effective treatment is available once the illness has developed. Yellow fever illness may however be avoided by elimination of mosquito bites and by vaccination.
Yellow fever is one type of illness called haemorrhagic fever and is transmitted by mosquito bites. The causative virus belongs to a family of viruses called Flaviviruses. Most commonly, yellow fever is transmitted by a type of mosquito called Aedes which is found in many areas around the world including northern Australia. Normally, the Aedes mosquito bites during daylight hours. In addition to humans, transmission occurs between wild populations of monkeys. The vector mosquito is prevalent through much of Asia, Pacific and other regions hence the vigilance by international customs officials in policing yellow fever vaccination requirements. Transmission of the illness is predominately in jungle areas but cases occur in urban areas in certain countries. During the last few decades, the number of cases of yellow fever has increased perhaps due to movement of population, increased urbanisation in regions of transmission and possible effects of climate change. Transmission of yellow fever illness may occur in altitudes of up to 2,500 metres in some locations.
Symptoms of yellow fever normally develop about 2-5 days after the initial mosquito bite. Typical features include fever, muscular pain, vomiting, jaundice and bleeding. Two phases of illness are often described. An initial flu-like illness normally develops followed by a period of improvement. In severe or complicated cases more sinister features such as jaundice or bleeding may develop. If feature of severe disease such as bleeding or jaundice manifest, the illness is often fatal .In severe cases the illness involves multiple organs including liver and kidneys. During outbreaks, a high percentage of cases are fatal with numbers up to 60 per cent of unvaccinated individuals being recorded.
According to the World Health Organisation (WHO) about 200,000 cases of clinical yellow fever occur each year throughout the world. The highest yellow fever risk occurs in West Africa but the illness is reported in other areas of tropical Africa as well as South America. In the last century or so cases have only been reported in Africa and South America however potential transmission could occur in other regions where suitable mosquito vectors exist. The risk for an individual traveller to an affected region depends on many factors and must be assessed on a case by case basis. During your consultation at our clinic, our doctor will make an assessment of your personal yellow fever risk and determine if a yellow fever vaccination is appropriate.
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