Dengue

Dengue is caused by the virus of the same name, from the Flaviviridae family. Four different serotypes of dengue virus have been isolated, classified as DENV-1, DENV-2, DENV-3 and DENV-4. A person can develop disease from any of these, even if infected in the past with another serotype. Primary infection, usually caused by a single serotype, is believed to result in permanent immunity to that serotype, while immunity with the other serotypes is only partial and temporary. Subsequent infections (secondary infections) caused by a serotype different from the previous one may therefore increase the risk of developing severe dengue, due to a very complex immune mechanism that results in an altered response to infection.

he transmission of dengue occurs as a result of the bite of female mosquitoes of the genus Aedes that have fed on the blood of infected individuals. Characterized by black bodies with white stripes and by the fact that they are active both day and night, they are two species also involved in the spread of other dangerous diseases such as yellow fever and dengue. Aedes aegypti is the main vector and is usually found in tropical and sub-tropical regions. Aedes albopictus is what we call the "tiger mosquito" and is found in more temperate areas of Europe, Asia and Africa. Direct human-to-human transmission, on the other hand, is extremely rare, possible only through direct contact with infected blood.

Dengue is endemic in more than 100 countries, from Africa, the Americas, Eastern Mediterranean, to Southeast Asia, Western Pacific, and throughout tropical regions, with local variations in risk determined by rainfall, temperature, relative humidity, and rapid urbanization in the absence of urban planning. The epidemic trend is characterized by an increasing pattern, with 1.2 million cases recorded in the Americas, Southeast Asia, and Western Pacific in 2008 and more than 3.34 million in 2016. The increase in new dengue cases can also be attributed to the spread of the virus to new areas: urbanization and climate change are factors that allow the vector mosquito to find new habitats in which to proliferate, while intercontinental travel can facilitate the transfer of the mosquito or the virus, fostering dengue outbreaks even in areas that had never experienced the disease.

The first outbreak in Europe was in 2012, on the island of Madeira, Portugal, where the virus infected more than 2,000 people. In 2015, an indigenous transmission of Dengue virus (DENV-1) occurred in the south of France, in Nimes, causing 7 cases of infection. The country, like many others in Europe, is home to the tiger mosquito, which allowed it to spread. The case identified as primary was imported from French Polynesia. In 2017, only imported cases occurred in Europe: 23 European countries reported 2026 cases of Dengue virus. Germany reported the highest rate (31.3%), followed by England (23%), France, Spain, and Sweden. In August 2020, there was one case of dengue contracted on Italian soil, in Veneto.

The incubation period of dengue varies from 5-6 days, which is followed by a broad clinical spectrum, from a subclinical or asymptomatic form (in which people do not even realize they are infected), to symptomatic forms characterized by even high fever persisting for more than ten days, muscle and joint pain, and a pinkish rash spread particularly over the skin of the trunk.
In more severe cases, there is up to flu-like symptoms and liver or encephalitic disorders. Some individuals develop a severe form of dengue, characterized by severe bleeding, multi organ failure (MOF) and plasma leakage. In this form, first identified in the 1950s and now prevalent in most Asian and Latin American countries, there is a real risk of death if not managed appropriately.

Suspicion for dengue may result from clinical examination of the patient, with observation of manifested symptoms, or from history (e.g. recent travel to endemic area).
Generally, diagnosis of the virus is based on laboratory tests looking for specific antigens, identification of the virus by PCR test, or analysis of blood parameters.

There is no specific treatment for dengue. Treatment is based on treating symptoms and maintaining vital functions.
For classic dengue, rest and control of dehydration is usually sufficient, with treatment of specific symptoms with antipyretics and analgesics. Aspirin (acetylsalicylic acid) drugs, which can promote or aggravate bleeding, should be avoided.
The hemorrhagic form must be followed carefully, replenishing fluids and minerals intravenously, while blood and plasma transfusions may be necessary in severe cases.

Prevention for dengue transmission begins with proper behavioral prophylaxis, especially during the day, a time when mosquitoes are most active.
- Use an effective mosquito repellent.
The Centers for Disease Control and Prevention (CDC) recommends repellents with the following active ingredients: DEET (>25%); Picaridin; IR3535; Eucalyptus Lemon Oil (OLE); Para-menthane-diol; 2- undecanone.
- Cover up.
Use clothing that covers your legs and arms, preferably light colored.
- Check the environment around you
Standing water is a perfect habitat for mosquitoes to breed. Make sure there is no stagnant water in: discarded tires or industrial containers, swimming pools, storm drains and saucers. To reduce the risk ti transmission, systematic control through pest control campaigns against the Aedes population turns out to be a key intervention.

Qdenga (trade name of the drug) is a live attenuated vaccine that can protect against the 4 serotypes. It is administered subcutaneously in the upper arm (deltoid muscle) starting at age 4 years, and involves the administration of two doses, spaced three months apart. There is currently no data for when to administer a booster dose; a booster dose will probably be recommended in the future after 3 to 5 years of age. The vaccine is well tolerated, and side effects are those common to other vaccines: pain at the site of inoculation, headache, muscle pain. It is the only vaccine that can also protect individuals who have contracted Dengue in the past (limitation of the previous vaccine), so it is a recommended vaccine for all International travelers.