Dengue fever circumstances are exploding in mainland France: what do that you must know?

Dengue fever circumstances are exploding in mainland France: what do that you must know?

An unprecedented variety of dengue circumstances have been recognized in mainland France since mid-summer. Certainly, almost forty “indigenous” circumstances – in different phrases, infections contracted on nationwide territory, with out the sufferers having traveled overseas – had already been reported in mid-September, which is greater than the cumulative whole of the final 10 years.

The illness has additionally declared itself in departments the place it had by no means been detected till now. Whereas the variety of infections will possible proceed to rise within the days and weeks to return, which areas are affected? What are probably the most believable causes of this distinctive state of affairs? And why can this example be worrying?

Within the Alpes-Maritimes, the most important outbreak ever recognized in metropolitan France

Presently, of the 5 departments affected by the illness, three are situated within the Occitanie area and two within the Provence-Alpes-Côte d’Azur (PACA) area.

In Occitania, 4 circumstances have been recognized in the identical habitat, within the city of Salvetat Saint-Gilles, 20 km west of Toulouse, in Haute-Garonne; 3 circumstances have been reported within the commune of Andrest and that, 15 km away, of Rabastens-de-Bigorre, within the Hautes-Pyrénées; 1 case was detected in Perpignan, within the Pyrénées-Orientales. The dengue virus had by no means been recognized in these final two departments.

Within the PACA area, the 2 departments affected are the Var, with six circumstances recognized in Fayence and, above all, the Alpes Maritimes with 26 circumstances recognized in three municipalities situated lower than 10 km away from one another: Saint-Jeannet, Gattières and La Gaude. The geographical and temporal proximity – they have been declared over a month – of those new circumstances leans in favor of a single and identical episode of circulation of the virus in these three municipalities. This focus is already the most important ever recognized in metropolitan France. It’s nonetheless lively, with the final circumstances recognized in early September. Different circumstances will possible be recognized quickly.

Till now, the variety of autochthonous circumstances of dengue fever remained very restricted in metropolitan France. It was estimated at lower than thirty for the reason that first case recognized in 2010, with fairly often just a few circumstances recognized per 12 months.

The variety of circumstances reported this 12 months subsequently already exceeds all of the circumstances recognized over the previous 15 years.

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Notice additionally that dengue is usually asymptomatic (in about 70% of circumstances), it might go largely unnoticed. Moreover, with the Covid-19 pandemic, the prognosis of different viral ailments has in all probability been underestimated over the previous two years. This may occasionally have involved particularly varied arboviruses, together with dengue fever. The precise variety of circumstances is subsequently in all probability tremendously underestimated.

Why such an explosion? Whereas it was tough to anticipate a rise within the circulation of dengue fever such because the one we’re experiencing in 2022, in recent times a number of precursors have foreshadowed a rise in vector-borne ailments.

The vector mosquito has invaded our territory

Distribution of the tiger mosquito in mainland France and Corsica, in January 2022.

Ministry of Solidarity and Well being

The virus that causes dengue fever is transmitted by mosquito species belonging to the genus Aedesof which the tiger mosquito is a component (Aedes albopictus). Nonetheless, since its first detection on our territory, in 2004 in Menton, this small black mosquito with a physique and legs striped with white native to Southeast Asia and the Indian Ocean has not stopped rising its French distribution space.

In lower than 20 years, it has invaded 67 out of 96 metropolitan departments (in comparison with solely 58 in 2020!). Its unfold all through the territory is inexorable.

The tiger mosquito is particularly recognizable by its white striped legs.
The tiger mosquito is especially recognizable by its white striped legs.

The supply of serious discomfort in the summertime interval (some vacationer areas are infested with it), the tiger mosquito is able to transmitting, along with the dengue virus, varied viruses chargeable for sicknesses in people, together with Zika or chikungunya virus. Its extension on our territory will increase the chance of spreading the ailments they trigger.

Presently, amongst these three viruses chargeable for tropical ailments, the dengue virus is probably the most current in metropolitan France, notably within the southern areas, the place the density of tiger mosquitoes is the very best.

A danger elevated by environmental and climatic adjustments

Climate situations, particularly temperature, air humidity and precipitation, have an effect on the geographic distribution and exercise of mosquitoes. Specifically, they promote their proliferation and their lifespan.

The summer season we skilled, distinctive for its alternation of scorching warmth and intense wet episodes, notably within the southern areas, led to a big enhance within the variety of mosquitoes.

Certainly, if their eggs want water to finish their growth course of, they’re however very resistant within the surroundings. Within the occasion of a drought, they will stay viable for as much as a number of years, permitting them to outlive till the situations for his or her hatching are favorable.

This explosion in mosquito populations has elevated the chance of transmission of the dengue virus, itself already elevated by the resumption of worldwide commerce and tourism.

Tourism and commerce promote the unfold of pathogens

Industrial or vacationer exchanges, which have been rising exponentially for a number of a long time, can facilitate the unfold of viral ailments, and particularly ailments unfold by vectors similar to mosquitoes.

Proof of the significance of those components, throughout the Covid-19 pandemic, the variety of circumstances of dengue fever infections from individuals getting back from journey exterior the Antilles decreased significantly, primarily because of the drastic drop in worldwide air transport. With the clear restoration in air visitors this 12 months, a rise in imported circumstances has been noticed: from Could 1 to September 2, 2022, Public Well being France counted 165 imported circumstances of dengue fever in France, i.e. already as many as for the entire of France. 12 months 2021…

These imported circumstances are as many dangers of the looks of “native” outbreaks, when the mosquito vector of the illness is current on the spot. And this, particularly since dengue fever is the most typical and widespread arbovirus on the planet.

How is dengue transmitted?

Originating in Africa, the dengue virus is a arbovirusfrom the English “ARthropod-BOrne VIRUS”, a virus transmitted by bugs that feed on blood. It belongs to the genus flavivirussimilar to Zika virus, or yellow fever and West Nile viruses, different arboviruses.

When a mosquito bites an contaminated particular person, it ingests the blood through which the dengue virus is current. The latter will then multiply within the physique of the mosquito, which can transmit it to a different particular person throughout a brand new chew.

The primary circumstances of dengue fever have been recorded within the 18th century on the American continent. This situation is well-known in lots of tropical and subtropical areas of the globe, from Africa to Asia through Latin America. The French abroad territories will not be spared: Reunion, Guadeloupe or Martinique have suffered recurrent epidemics in recent times.

A illness that’s typically asymptomatic, however generally critical

Dengue fever is usually known as “tropical flu”, as a result of its signs are most frequently flu-like: sufferers have fever, complications, physique aches… They will additionally generally develop a rash.

Manifestations of the illness happen 3-14 days after the mosquito chew, with a mean of 4-7 days. The affected person typically recovers spontaneously in a number of days, however vital fatigue persists for a number of weeks.

Presently, there is no such thing as a particular remedy for dengue fever. A vaccine exists (Dengvaxia), however it stays little used attributable to many limitations concerning its use. This vaccine has the drawback of accelerating the chance of hospitalization and extreme dengue in individuals not beforehand contaminated with the dengue virus. It’s primarily prescribed to individuals residing in endemic areas, and who’ve already been contaminated with the dengue virus.

The administration of the illness consists primarily of treating the signs, particularly ache and fever. Aspirin and non-steroidal anti-inflammatory medication are formally contraindicated because of the danger of bleeding.

The principle drawback related to dengue fever is the chance of growing what is known as extreme dengue fever or dengue hemorrhagic fever, which will be sophisticated by a state of typically deadly shock. Dengue hemorrhagic fever is manifested particularly by respiratory misery related to a number of hemorrhages.

Fortuitously, this extreme type of dengue impacts solely a small proportion of contaminated individuals: between 1% and 5% of circumstances. Some individuals additionally develop extreme neurological harm (similar to encephalitis) however these issues are extraordinarily uncommon.

4 completely different virus varieties, however no cross-immunity

There are 4 various kinds of dengue virus, that are differentiated from one another by refined adjustments of their antigens (antigens are buildings whose detection by the immune system results in its response and the manufacturing of antibodies – it might s act of proteins, lipids, sugars, and many others.).

These 4 dengue virus serotypes, named DENV-1, DENV-2, DENV-3 and DENV-4, though comparatively related, are completely different sufficient to not confer long-term cross-protection. In different phrases, if an infection by one of many serotypes immunizes us in opposition to it, it doesn’t supply safety in opposition to the opposite three. You possibly can subsequently be consecutively contaminated with the 4 dengue serotypes throughout your lifetime.

In mainland France, a minimum of two serotypes, DENV-1 and DENV-3, have been recognized this 12 months. Which means that the dengue virus has been launched into the territory a number of instances this summer season.

Mosquito management as a way of prevention

After the invention of circumstances of an infection, the identical situation takes place: mosquito management operations are carried out close to the circumstances detected, accompanied by awareness-raising actions with the general public and well being professionals (in addition to throughout surveys door-to-door), carried out in collaboration with the ARS, Public Well being France and mosquito management businesses similar to Altopictus or the Interdepartmental Mosquito Management Settlement.

Presently, one of the best methods to stop the unfold of viruses similar to dengue, transmitted by mosquitoes, is to restrict the proliferation of those bugs and to guard themselves from their bites.

To scale back the event of mosquito larvae, it is suggested to empty all containers of stagnant water, together with flower pot cups and watering cans, and to cowl rainwater containers, particularly in periods of heavy rainfall. . To restrict the chance of being bitten, it is suggested to make use of appropriate repellents, and to put on free and overlaying clothes.

Fortuitously, in our nation, the specter of arboviruses, together with dengue fever, stays sporadic in the meanwhile and the chance of an epidemic is restricted. Strengthening surveillance networks presently stays probably the greatest methods for combating these new threats which can be tough to anticipate.

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