Dengue: symptoms, in France, by the tiger mosquito

Dengue is a disease present in France. According to Public Health France, since 1^Ahem from May to September 2, 2022, 139 cases imported dengue has been identified in France including 133 in departments with documented establishment ofAedes albopictusthe famous tiger mosquito These cases are recorded mainly in the south of France, in the Occitanie and Paca regions. When dengue cases are identified in France, Epidemiological investigations are carried out to identify possible other cases and precisely define the transmission area. Health professionals in the sectors concerned are made aware of the diagnosis and report other cases. Mosquito control actions are also carried out.

“In recent years, Aedes albopictus, the vector of dengue fever in Asia, has become established in North America and Europe, including France, where 2 first autochthonous cases were identified in 2010 in Nice“ reports Professor Anna-Bella Failloux, head of the “Arboviruses and vector insects” research and expertise unit at the Institut Pasteur. According to Public Health France, since 1^Ahem from May to September 2, 2022, 139 cases imported dengue has been identified in France including 133 in departments with documented establishment ofAedes albopictusthe famous tiger mosquito These cases are recorded mainly in the south of France, in the Occitanie and Paca regions.

List of departments with documented implementation ofAedes albopictus at 1^Ahem May 2022

Ain, Aisne, Alpes-de-Haute-Provence, Alpes-Maritimes, Ardèche, Ariège, Aude, Aveyron, Bas-Rhin, Bouches-du-Rhône, Cantal, Charente, Charente-Maritime, Cher, Corrèze, South Corsica, Côte d’Or, Two – Sèvres, Dordogne, Doubs, Drôme, Essonne, Gard, Gers, Gironde, Haute-Corse, Haute-Garonne, Hautes-Alpes, Hautes-Pyrénées, Haute-Savoie, Haut-Rhin, Hauts-de-Seine, Haute-Vienne, Hérault, Indre, Indre-et-loire, Isère, Jura, Landes, Loire, Loire Atlantique, Lot, Lot-et-Garonne, Lozère, Maine-et-Loire, Mayenne, Nièvre, Paris, Puy-de-Dôme, Pyrénées -Atlantiques, Pyrénées-Orientales, Rhône, Saône-et-Loire, Savoie, Seine-et-Marne, Seine-St-Denis, Tarn, Tarn-et-Garonne, Val-de-Marne, Var, Vaucluse, Vendée, Vienne , Yvelines, Val-d’Oise, Meurthe-et-Moselle, Loiret.

Dengue is a disease caused by a virus transmitted to humans by female mosquitoes of the genus Aedesmainly the species Aedes aegypti. Aedes albopictus, better known as the tiger mosquito can also transmit dengue. It is a very often mild disease. The dengue virus is a arboviruses (insect-borne virus) divided into 4 serotypes :

• DEN-1,
• DEN-2,
• DEN-3
• DEN-4.

In people who have been infected, recovery leads to lifelong immunity against the serotype causing the infection, but not against the other three. Therefore, a person can become infected with each of the four dengue serotypes during their lifetime.

The vector of the dengue virus is the Aedes aegypti mosquito and the tiger mosquito, which live in urban areas and reproduce mainly in containers with stagnant water. In Aedes aegypti, cIt is the female that itches, mainly during the day, with a peak of activity in the early morning and in the evening before nightfall. Aedes albopictusa daytime activity, present in Asia, has spread to North America and Europe. Endowed with great ease of adaptation in temperate zones, was introduced in 2004 in the Maritime Alps, and its area of ​​implementation continues to expand”recalls Professor Anna-Bella Failloux, head of the “Arbovirus and vector insect” research and experience unit at the Institut Pasteur.

A person infected with dengue is not contagious to another human being.

► Pollution mode is classic : the mosquito becomes infected by biting an already infected person and, therefore, can transmit the virus by biting another individual a few days later. Once in the body, the the virus multiplies and persists for 3 to 10 days. The person infected with dengue is not contagious to another human being, instead it can infect other mosquitoes of the Aedes genus if it is bitten again in a period that goes from 1 to 2 days before the onset of symptoms and up to 7 days later. The virus can, more rarely, be transmitted by transfusion or transplantation (of organs or cells).

the dengue is asymptomatic in 50 to 90% of cases (variable percentage according to epidemics). Symptoms are often similar to those of the flu (sudden high fever, headache, nausea, vomiting, joint and muscle pain, and rash measles-like) manifesting within 3 to 14 days (average incubation period 4-7 days) after mosquito bite. However, classic dengue, most often benign but disabling, can be complicated by hemorrhagic forms. Consult your doctor immediately in the presence of suggestive symptoms (sudden-onset high fever, muscle or joint pain, eye pain, fatigue, headache), especially if they appear within 15 days after returning from a trip to a tropical area.

Dengue affects infants, young children and adults equally. So there are no people at higher risk than others. However, people who live in areas with high circulation of the virus (see below) are at higher risk.

Two thousand five hundred million people live in risk areas. Dengue is rampant mainly throughout the intertropical zone. Long limited to Southeast Asia, it continues to spread to the Indian Ocean, the South Pacific, the West Indies french andLatin Americawhere reported annual cases increased 60-fold between 1989 and 1993 compared to the previous period (1984-1988).

Nonsteroidal anti-inflammatory drugs and aspirin are contraindicated.

Early diagnosis can be made by look for NS1 antigen, a dengue virus protein detected in the serum of people with dengue at the onset of fever; identification of the virus can also be carried out early.
the look for IgM type antibodies, it only becomes positive around the 6th or 7th day of fever and persists for an average of 2 to 3 months. Other more sophisticated biological tests, such as PCR or viral cultures, are reserved for research or the highly specialized laboratories of reference centers. “The biological diagnosis allows the declaration of the disease; instead, if we accept the theory according to which a second infection could be more seriousit is preferable for a person to know whether or not they have already had an episode of dengue, to adopt even more drastic preventive measures”says Professor Failloux.

The diagnostic approach recommended in the ministerial plan “chikungunya and dengue anti-dissemination” is as follows:

• Up to 5 days after the onset of signs (D5): RT-PCR
• Between D5 and D7: RT-PCR and serology
• After D7: serology only (IgG and IgM) with a second confirmation sample at least 10 days after the first sample

Blood samples can be taken by any medical biology and analysis laboratory.

There is not no specific treatment dengue. Treatment is symptomatic, aimed at fighting pain and fever. Nonsteroidal anti-inflammatory drugs (ibruprofen, etc.) and especially aspirin are contraindicated due to thrombocytopenia (low platelet count) and bleeding risk.

There is no vaccine against dengue. Therefore, prevention is based on effective vector control measures.

According to the ARS, to avoid mosquito bites, It is advisable:

• wear a coat and loose clothing, until impregnated with insecticide for fabrics;
• use a skin repellent, preferably morning and evening, recommended by a pharmacist, on exposed skin areas;
• if necessary, use mosquito nets on the openings (doors and windows);
• use crib mosquito nets for newborns;
• use electric diffusers inside houses;
• use insecticide coils only outdoors;
• use air conditioners or fans that interfere with mosquitoes.

To limit the development of mosquitoes around your homesuits :

• empty, store, or discard any container that may hold water;
• cover water supplies with mosquito netting or cloth to make them airtight;
• clean gutters and gutters;
• prevent illegal dumping of waste.

Dengue virus infection during pregnancy does not cause no increased risk of disease or worsening of disease in the mother. The rate of malformations does not increase, but cases of congenital dengue are occasionally observed. Premature births and abortions are possibly more common in dengue patients. Infection of the fetus occurs before birth, during the last weeks of pregnancy.

Clinical surveillance should be maximum around the fourth day.

In children under 15 years of age, hypovolemic shock it can set in (cooling, clammy skin, and a faint pulse indicating circulatory failure) and cause abdominal pain. Appropriate medical treatment is necessary to avoid complications and the risk of death. An intravenous infusion should be started quickly to restore blood volume because bleeding can cause significant blood loss.

Severe dengue is a life-threatening complication due to the occurrence of a State of shock or bleeding complications. Generally, after a flare-up of fever, the infection starts again and can progress in rare cases (1% of cases in people with dengue symptoms) to severe dengue. Clinical surveillance should be maximum around the fourth day. dengue usually heals in 2 weeks, but the recovery time can take several weeks. Patients can feel quite tired during this period and develop depressive symptoms.

Produced with Professor Anna-Bella Failloux, head of the “Arboviruses and vector insects” research and experience unit at the Institut Pasteur.