DISTRIBUTION
Dengue fever occurs frequently in more than 110 countries, mostly in Asia, in the Pacific and Caribbean regions, America, and Africa. It is highly mobile, spreading by infected travellers as well. The number of infectious cases has increased dramatically over the last few decades, and large epidemics have occurred. It can be brought into the EU by infected tourists returning home but locally acquired cases are also increasing. In 2024, Europe recorded 213 cases in Italy, 85 in France, and 10 in Spain. The risk of transmission by blood donation is currently under investigation.
AFFECTED HOST SPECIES
Its main hosts are humans. In tropical and subtropical areas, it spreads and survives in a human-mosquito cycle. Cases indicating illness in non-human primates have been found in Southeast Asia and West Africa, but there is no evidence that they are responsible for the development of major epidemics.
TRANSMISSION AND VECTORS
Humans can be infected by bites from the Asian tiger mosquito (Aedes albopictus) or the yellow fever mosquito (Aedes aegypti). Dengue fever is only transmitted by the bite of an infected virus-carrying mosquito. The risk is higher in populated areas because the yellow fever mosquito species is found in urban environments.
SYMPTOMS
In 40-80% of cases, the infection is asymptomatic. After a latency period of eight to ten days, mild and usually flu-like symptoms may appear. Clinical symptoms include sudden fever, severe headache, eye socket pain, muscle pain, joint pain, skin rashes, and mild bleeding. Dengue fever is also known as “break-bone fever” because it can cause such severe pain that the patient feels as if his bones are breaking. The illness rarely lasts longer than ten days, but recovery can take a long time. Usually less than 5% of cases cause serious illness, and a fraction of these result in death, mainly among children and adolescents. A more serious form of dengue fever is dengue hemorrhagic fever or dengue shock syndrome (DHF/DFF), which is associated with increased vascular permeability and thus life-threatening bleeding.
TREATMENT, PREVENTION
Currently, two vaccines are available, one is Dengvaxia, which can be given to children aged 9–16 only if they have already had a dengue infection and live in a high-risk area, the other is Qdenga, which can be given from the age of 4, and contains a weakened virus. An important element of prevention is protection against mosquito bites. Infection can be detected serologically by identifying specific antibodies about 5–6 days after infection.