Introduction
Yellow fever is an infectious disease transmitted by mosquitoes. The virus that causes the disease is called yellow fever virus. The disease is usually characterized by fever, nausea and vomiting and can subside on its own or, in more severe cases, can lead to death if left untreated. The reasons for this are bleeding in the gastrointestinal tract and sudden liver and kidney failure as complications. Yellow fever is most common in sub-Saharan Africa and South America, which is why vaccination against yellow fever is arranged before travelling to these areas.
In which areas is yellow fever present?
Yellow fever occurs in Africa, South America and Central America. Since the affected areas occur in the area of certain latitudes, one speaks also of the so-called “yellow fever belt”. In Africa, above all the areas south from the Sahara, that are on height of the equator, are affected.
Popular, in the yellow-fever-area lying safari-destinations are Z. B. Kenya, Tanzania. The West African states on the Gulf of Guinea are also particularly affected.
In South America yellow fever is more common in the northern part of the continent: Brazil, Peru, Bolivia, Venezuela, Ecuador and Colombia. Argentina and Chile are not affected. In Central America yellow fever is less common than in South America, mainly the Caribbean island states are affected: Cuba, Dominican Republic, Jamaica and Haiti. Yellow fever can be distributed very differently in different affected countries, so it is advisable to seek medical advice before travelling. No cases of yellow fever have been reported from Asia to date, although the climatic conditions necessary for transmission are also present there.
Which mosquitoes transmit yellow fever?
The yellow fever virus belongs to the flavivirus family and is found mainly in the tropical and subtropical zones of Africa and South America. In the past, the disease only occurred in Africa, but was also spread to South America through the slave trade. The mosquito, which transmits the yellow fever virus, can also be found in Asia, but the disease does not occur there.
There is no explanation for this phenomenon. The yellow fever virus is transmitted from the mosquito to humans by a mosquito bite. The only organisms in which the virus can survive are primates (humans and apes) and the mosquitoes themselves.
According to statistics, about 200,000 people fall ill with yellow fever in risk areas every year, 30,000 of them die. In Germany, the disease must be reported by name. A distinction is made between two types of mosquito, both of which cause yellow fever: Aedes aegypti and jungle mosquitoes (e.g. Aedes africanus in Africa and Haemogogus mosquitoes in America).
Jungle mosquitoes can transmit the yellow fever virus through their bite to many different species of monkeys, which are the natural reservoir of the pathogen. However, jungle mosquitoes can also infect people living in tropical rainforests with yellow fever. If these infected people later stay in more urban areas, the yellow fever virus can be ingested by the mosquito Aedes aegypti.
The reason for this is that this mosquito breeds near human settlements. Thus, the mosquito Aedes aegypti becomes a carrier of the yellow fever virus from human to human, which is called a “vector”. The mosquito Aedes aegypti can cause large outbreaks of the disease in areas with many people not vaccinated against yellow fever.
The virus belongs to the flavivirus family (Latin flavus = yellow). These viruses have a genetic material consisting of a single strand of RNA. They have in common that they are all transmitted by mosquitoes or ticks. The yellow fever virus infects cells of the immune system, e.g. scavenger cells, and starts here with the multiplication of the genetic material.
