Reader TTS

Cases of dengue fever caught via a mosquito bite are on the rise due to an increasing number of tiger mosquitoes in the country, health authorities and specialists have warned.

This year 18 people in the southern region of Occitanie have been diagnosed with the illness, and increased numbers of cases are also being observed every year in the Mediterranean regions.

These are ‘native cases’ (autochthonous, or autochtones in French), meaning that they are diagnosed in people who have not travelled to an area of the world which is typically associated

with dengue.

This has been blamed on rising numbers of tiger mosquitoes; and hotter temperatures due to climate change, which help the mosquitoes proliferate.

It has been mandatory for doctors to report cases of dengue since 2006, and each case requires a health investigation.

In 2022, there were 66 cases of native dengue reported, of which the majority were in Paca (Provence-Alpes-Côte-d'Azur). The second most affected region was Occitanie, where there were 12

cases.

This represented a sharp rise with just 48 cases identified in total between 2010-2021.

Specialists are now warning that native cases of dengue (as well as chikungunya and Zika, which are also spread by tiger mosquitoes) are likely to rise further in coming years.

“The increase in the number of cases, particularly indigenous cases, is due to the growth in the population of mosquitoes, which are the vectors of the infection,” said Dr Charlotte Boullé,

infections specialist at the infectious and tropical diseases department at Montpellier University Hospital, to France 3.

“Systematic case-finding and reporting are also playing a role,” she said.

She added that native cases are firstly linked to non-native cases. This is because, to spread the illness, a mosquito must first bite an infected individual.

Dengue is most common in areas including South and Central America, the Caribbean, the Philippines, parts of Southeast Asia, India, and Bangladesh.

Severe outbreaks are also relatively common in Singapore, and in the French overseas territories of Martinique and Guadeloupe.

The number of cases imported into mainland France varies every year. However, the total in 2023 is expected to be significantly higher than that of 2022 (1,099 in 2023 compared to 378 in

2022).

This is mainly due to ongoing epidemics in French overseas territories where infected people visiting or returning to France bring the infection to mainland France.

Dr Boullé warned that increased cases each year - and the continued spread of tiger mosquitoes - could mean that the illness becomes ‘normal’ in France.

She said: “Our fear is that, as the tiger mosquito spreads across mainland France, dengue fever will become an epidemic every year, and ultimately an endemic disease.”

In a recent advisory, the committee for health risks, Covars (le Comité de veille et d'anticipation des risques sanitaires), said that in future, the country can expect to see more cases of

dengue and new reports of Zika and chikungunya.

“These [viral illnesses] could become public health problems,” it said.

To prevent increased spread, people who return from at-risk countries should take extra steps to protect themselves from mosquito bites for two weeks once they get home, even if they have no

symptoms of dengue.

This helps to prevent the virus from spreading via its vector, the tiger mosquito.

A vaccine against dengue already has approval for use in France but it is rarely used. Also, it is currently only allowed for people aged nine to 45 who have a documented history of dengue

infection or who live in a dengue area.

In areas where dengue - and growing numbers of tiger mosquitoes - are identified, authorities now tend to carry out anti-mosquito operations.

This typically includes spraying anti-mosquito insecticide and using other anti-mosquito methods in the local environment overnight.

Local residents are warned in advance to stay indoors during the spraying.

The best way to stop the spread of mosquito-borne diseases is to prevent the mosquitoes from becoming attracted to your home or garden.

Health authority Anses gives the following tips to help with this:

Dengue does not typically cause a cough, runny nose, sore throat, breathing difficulties, and/or infected wounds. If you have these issues (even in combination with the symptoms above), it

may point to a different condition, not dengue.

Many cases of the illness are asymptomatic, but symptoms can come on between three to 14 days after being bitten.

Around 1% of cases can become more severe, and cause a very high, persistent fever and sometimes-fatal haemorrhaging.

If you believe that you may have dengue you are advised to report it to your doctor as soon as possible even if you have not travelled to an at-risk area.

There is no cure for dengue currently; patients are advised to rest and treat the symptoms.

The vast majority of cases will go away on their own after a few weeks.

Having first been identified in France in 2004, the insects were initially common in the south, but rising temperatures have seen them spread north. Tiger mosquitoes are now in 71

departments in France, and counting.

The weather and global warming are considered major factors. Rainy-but-warm days offer the perfect conditions for the insect to proliferate and spread.

They can start biting in early summer and continue into autumn. And, unlike ‘regular’ mosquitoes, they do not only bite at night.

They tend to bite during the day, and are attracted by stagnant water and warmer temperatures.

“This is a completely normal seasonal dynamic,” said Guillaume Lacour, medical insect expert for Altopictus, a company specialising in monitoring and combating the tiger mosquito, to La

Dépêche.

“It is common to see an abundance [of the mosquitoes] until at least mid-October. There was a peak in the south-west between May and July, and since August we've been back to the usual

pattern,” he said.

Anna-Bella Failloux, entomologist (insect expert) at the Institut Pasteur has said: “As time goes by, the mosquito is making its way to the north of the country.

“This is because the climate allows it and because it is a mosquito that is hyper-adapted to humans, which means that it will move along with them with transport.”

As of January 1, 2023, their presence has been confirmed in 71 departments.