Dengue fevers will become a major threat in the southern United States, southern Europe and new parts of Africa this decade, the World Health Organization’s chief scientist said, as warmer temperatures create conditions for the spread of mosquitoes that carry the infection.

The disease has long plagued much of Asia and Latin America and it is estimated that it causes 20,000 deaths every year.

The spread of the disease it has already increased eightfold globally since 2000largely due to climate change as well as increased human movements and urbanization.

Many cases go unreported, however in 2022, 4.2 million cases were reported worldwide and public health officials have warned that record levels of transmission are expected this year.

Bangladesh is currently dealing with the worst outbreak of the disease ever recorded in the country, with more than 1,000 deaths.

“We need to talk about taking much more action against dengue,” Jeremy Farrar, an infectious disease expert who joined the WHO in May this year as the agency’s chief scientist, told Reuters.

“We need to really prepare countries for how they will deal with the additional pressure that will come … in the future to many, many large cities.”

Farrar has spent 18 years working in Vietnam on tropical diseases, including dengue fever. He later led the global health charity Wellcome Trust and advised the UK government on the response to Covid-19, before joining the WHO in May this year.

Farrar said the infection is likely to “take off” and become endemic in parts of the United States, Europe and Africa – all regions where there was already some limited local transmission – as global warming makes new areas hospitable to the virus. mosquitoes that transmit it. This will create acute pressure on the hospital systems of many countries, he warned.

“Clinical care is really intensive, requiring a high ratio of nurses to patients,” he said. “I’m really worried about what will happen when this becomes a big issue in sub-Saharan Africa.”

Most people who contract dengue have no symptoms, meaning the proportion of cases is believed to be much higher than the numbers reported. Those who do develop symptoms experience fever, muscle spasms and joint pain, which is so severe that the disease is also called “broken bone fever.” In severe cases – less than 1% – it can be fatal.

There is no specific treatment for dengue, although a vaccine is available. Earlier this week, the WHO recommended Takeda Pharmaceuticals’ Qdenga vaccine for children aged 6 to 16 in areas where the infection is a major public health problem.

Qdenga has also been approved by the EU regulator, but Takeda withdrew its application to the US Food and Drug Administration for the vaccine earlier this year.

Preparing new regions of the world to deal with dengue means ensuring that public health funds are spent in the right areas, Farrar said, as well as how best to control mosquitoes.

Dengue is spread by infected Aedes aegypti mosquitoes, which behave differently than the mosquitoes that transmit malaria. For example they bite people indoors and they bite throughout the day and not just at night. They also breed in very shallow water.

Farrar said proper prevention includes patient triage plans in hospitals as well as scientific innovations combined with other important factors, such as urban planning to avoid areas of standing water near or inside homes.

“We need to coordinate various sectors that are not used to working together,” he said.