What is dengue fever and why is it so prevalent?

Dengue fever is mainly transmitted by the Aedes Aegypti mosquito, which lives in densely populated tropical climates and breeds in stagnant puddles.

HEALTH

Nicknamed "bone fever", dengue fever is one of the world's leading mosquito-borne diseases and infects tens of millions of people each year around the world.

About half of the world's population lives in high-risk areas, mainly in Latin America, Africa and Asia.

Epidemics ravaged Southeast Asia this year, infecting hundreds of thousands of people, killing hundreds and destroying health care systems as governments struggled to contain the untreatable virus.

While dengue, how does it spread and how can it be controlled?

How does it spread?

Dengue fever is mainly transmitted by the Aedes Aegypti mosquito, which lives in densely populated tropical climates and breeds in stagnant puddles.

Mosquitoes catch the virus in infected humans – even if they are asymptomatic – and pass it on to others through bites.

Infections have been steadily increasing worldwide since the 1970s due to rising temperatures and erratic monsoon rains associated with climate change, which provide ideal conditions for mosquito breeding.

Dengue fever is most prevalent in overcrowded areas. The worldwide urbanization on the fly has contributed to the spread of the virus, especially in fast-growing megacities like Manila, Rio de Janeiro, Ho Chi Minh City and Tegucigalpa.

A massive expansion of international travel and trade has also spread the fingerprint of dengue fever, allowing the virus to be transported around the world in a matter of hours and breaking loose in new communities.

Experts say that the widespread adoption of plastic is also to blame – storage containers, takeaway takeaway boxes, backyard pools, planters and kitchen urns all collect from the outside. water – an aggravated problem during dry periods.

"In times of drought, people are fetching water from containers – it's a place that dengue mosquitoes love to breed," said Gawrie Loku Galappaththy, a dengue specialist at Dengue. World Health Organization in the Philippines.

What does it look like?

His sinister nickname comes from intense flu-like symptoms of the disease: severe headaches, pain behind the eyes, pain throughout the body, high fever, nausea, vomiting, swelling of the glands or rashes.

This is very serious – and fatal – in children, especially young girls, although scientists do not know why.

Subcontracting one of the four dengue strains confers immunity only to this single strain. This is why adults in endemic areas are often safe as they have probably already done so.

But later, the removal of a different strain, called serotype, usually causes a more serious infection than the first time.

In the absence of known treatment for dengue, doctors can only help to alleviate the brutal symptoms of the virus, which can last for weeks and often make patients completely immobile.

Why have cases increased this year?

Formerly confined mainly to cities in tropical climates, dengue is present in at least 125 countries of the world. About 100 million people are infected each year and nearly 4 billion people live in areas exposed to dengue fever, according to Nature Microbiology.

The disease is cyclical – dramatic epidemics occur every few years – but climate change would have contributed to an increase in the number of cases in 2019, the hottest July ever.

"The extremely hot temperatures we have experienced this year" have probably facilitated its spread, said Rachel Lowe, Assistant Professor at the London School of Hygiene & Tropical Medicine, to the extent that mosquitoes are developing through warm weather.

Epidemics have occurred in several European countries where dengue fever was once marginal, while Latin American countries, including Brazil, Colombia, Honduras and Nicaragua, are facing an upsurge in cases.

How can it be contained?

In South-East Asia, insecticide misting is commonly used to kill mosquitoes, but it usually reappears after a few days and insects can quickly become resistant to chemicals.

The controversial vaccine developed by the French pharmaceutical company Sanofi Pasteur has been approved for use in 21 countries and in the European Union – but it is far from perfect.

The vaccine, called dengvaxie, requires three doses and should only be administered to people over nine years of age – the maximum age varying from country to country – who have already been infected with dengue fever.

In 2016, the Philippines was one of the first countries to use Dengvaxia in a mass vaccination program, but its failed deployment was blamed on the deaths of dozens of children and led to its eventual ban .

Several countries are also testing the so-called Wolbachia method and, although it is too early to say whether this approach works on a large scale, the first results are promising.

Mosquitoes are infected with the naturally occurring Wolbachia bacteria – which is mainly resistant to dengue fever – and are released to repopulate colonies of wild mosquitoes to reduce the transmission of the disease.