DENGUE, an endemic disease in India

The world of viruses has become more familiar to us over the last three years. The experts explained to us how they worked and made us understand that the fight we are waging against them has rarely ended in our favor until further notice.

The editorial contributes to our knowledge by focusing on the dengue fever that is rampant in India, especially in Tamil Nadu.

Dengue fever, a virus transmitted to humans by mosquitoes

The term “dengue fever” comes from the African Swahili and means “problem caused by an evil spirit”. The evil spirit in this case is a virus that is transmitted to humans by a mosquito of the genus tiger mosquito Singer. Not to be confused with the famous mosquito vector of malaria anopheles.

Dengue fever, an endemic disease in India

It is now assumed that half of the world’s population lives in a dengue risk zone (approx. 130 countries). Between 2000 and 2019, the number of cases increased eightfold (5.2 million cases in 2019). 70% of infections are registered in Asia.

Since 1990, India has experienced many epidemic phases. In 2009 there were 82,300 cases. In 2021 the number of infections was 193 245. The true number of cases is an understatement as most cases are mild or even asymptomatic and therefore go undiagnosed. In 2017, a study in 60 Indian districts found a seroprevalence of 49%.

In 2021, Uttar Pradesh (29,750 cases), Punjab (23,389), Rajasthan (20,749) and the city of Delhi (13,089) accounted for 45% of the cases. Tamil Nadu had 6,039 infections and Pondicherry 1,625 in the same year.

Dengue fever cases by state in India in 2021

At the end of August 2022, the total for Tamil Nadu was 3,528 cases; The projection for the full year reaches levels consistent with 2021, with cases multiplying at the time of the monsoon at the end of the year.

The dengue virus/mosquito duo Singer

Dengue is an infectious disease caused by a virus. Four variants of the virus are in action and unfortunately the immunity provided by infecting one variant does not protect against the other variants.

The disease is often asymptomatic. It manifests itself as a sudden fever, combined with severe pain and a rash. In rare cases, serious complications can occur.

Originally, dengue is an infection that occurs in tropical or intertropical areas. Globalization of trade and global warming are causing the disease to spread to more temperate areas today.

To expand its field of action, the virus uses the mobility of its means of transport, the mosquito. Singer. There are several types of mosquitoes Singer. In India there are two species, the mosquito Aedes Albopictus and the mosquito Aedes Egypti.

L’Aedes Albopictus, Called the tiger mosquito, it can be recognized by its white and black striped legs, it travels in containers and even tires. Its eggs can survive for a long time in a dry environment, but as soon as a little water moistens them, they hatch and reproduce. L’Aedes Egypti also has white and black striped legs but differs from theAedes Albopictus on the chest, which is decorated with a lyre. only the mosquito Aedes Albopictus spread all over the world until it reached temperate zones like France.

In France, the tiger mosquito is present in 67 urban departments. According to the latest figures published by the Public Health France website, 139 imported cases of dengue fever (acquired abroad and incubated in France) were currently diagnosed in France and 16 native cases in 2022.

The female mosquito Singera daily binder

It is the female that bites to feed on our blood. It works mainly during the day (unlike anopheles which stings in the second part of the night). It is very aggressive at dawn and dusk.

When the mosquito bites a person infected with dengue fever, the accumulated virus multiplies in his stomach for about ten days. The dose is then strong enough to infect the next person to be bitten. The first signs of the disease appear after the incubation phase, which lasts an average of 4 to 7 days.

Singeran urban mosquito

Singer is a predominantly urban mosquito. The females lay their eggs in small spaces that are likely to collect water: vases, saucers, used tires, poorly emptied gutters, various debris with stagnant water, plants likely to form water residues (bamboo, traveller’s tree…).

Singer does not like large bodies of water or rivers.

This is one of the reasons for the geographic distribution of infections in India. The vast majority are concentrated in cities or densely populated areas.

Studies have shown that families without access to running water have an increased risk of contracting dengue fever. They are forced to store stagnant water, thus providing privileged niches for egg laying.

Unplanned urbanization, the lack of water supply and drainage systems, the accumulation of garbage in India create ideal conditions for the spread of mosquitoes. Rising temperatures and changing precipitation patterns are exacerbating the situation. After all, preventive measures to contain the epidemic are not systematic and remain ineffective.

How to protect yourself from mosquitoes Singer

There is no specific antiviral treatment for dengue fever. In case of suspicion, the most common diagnostic method is the serological detection of antibodies. A vaccine that is effective for everyone is currently being studied.

The only effective prevention is to protect yourself from mosquito bites: repellent sprays or creams, coils, electric diffusers, long clothes, mosquito nets. All is well.

Indian health portal infographic on dengue fever protection – National Health Portal India

You have to remember that Singer bites during the day and that it is a small insect that stays near the ground most of the time. Feet and legs should therefore be covered as a matter of priority.

Also important is the elimination of all potential sites for egg laying and larval hatching: no standing water in saucers and other containers.

At the collective level, the fight against mosquitoes today takes various forms: spraying insecticides, releasing sterile male mosquitoes, releasing fish that eat mosquito larvae in ponds, etc.

The means developed in India are still limited and the population is not sufficiently sensitized to win the game.

WHO infographic on dengue fever

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