Visitors to France may bring home the deadly virus this summer

A disease expert has warned that 10 million people visiting France this summer could create a “super-spreader event” as they could silently take home a potentially deadly virus and spread it to the local population. Mark Booth, Senior Lecturer in Parasite Epidemiology at Newcastle University, has issued a warning about the Paris Olympics.

His warning comes after several people fell ill with dengue fever in Paris 2023, and millions of people are expected to visit the city this summer for the international games. The 2023 cases were the northernmost dengue outbreak ever recorded – and the mosquito-borne disease appears to have been picked up in Paris rather than by travelers to tropical destinations returning to the capital.

Writing for The Conversation, Mark Booth said: “The French government knows there is a dengue risk. In Paris, hundreds of places are regularly checked for the presence of dengue-carrying mosquitoes.”

Dengue can only be caught from a single mosquito bite – it cannot spread from person to person – but millions of people could pick up the infection from an Aedes mosquito and carry it back to their home countries. If they are then bitten by local mosquitoes, the disease will spread.

Mark said: “Aedes has spread considerably more than in 2016 and the number of dengue cases worldwide has increased dramatically over the same period. In 2016, 5.2 million cases were reported worldwide. By mid-2024, there were already 7.6 million cases.

“Visitors from more than 200 countries are expected in France for the Olympic Games. Many of these countries are already experiencing dengue this year. For the Paris Olympics to become a super-spreading event, several factors must overlap. There must be enough mosquitoes, enough susceptible and already infected people, enough time and enough mosquito bites.

“The tiger mosquito is perfectly adapted to the urban environment of Paris. It only needs the smallest amount of water in a small container to lay its eggs. It feeds preferentially on humans, at dawn and dusk. The eggs themselves can last in dry conditions for months. Again, the eggs will hatch.

“What makes this situation potentially dangerous for Paris is that some of these mosquitoes may already have dengue inside them, passed down from their mother. This could significantly reduce the number of bites needed to start an epidemic.

“In the time frame of the Olympics, an infected athlete or spectator could get bitten once by a mosquito and seed an epidemic within a week or so. Each female mosquito can lay up to 200 eggs at a time. Most cases of dengue are asymptomatic. People infected before or during the Olympics may have no idea they have the virus. He could carry the virus back home and start an epidemic there without ever knowing.

“Whether people get sick or not, they carry the virus and can pass the infection on if they are bitten by an Aedes mosquito. At this year’s Rio Carnival, an outbreak of dengue days before the event led to a public health emergency. called, but the event was not cancelled.

“There will be no public health emergency in Paris because the event itself is the risk factor. Anyone who lives, works, visits, competes, volunteers or even passes through Paris during the Olympic period will be part of a huge natural experiment – whether they know it or not.”