The potential of the Paris Olympics serving as a hotspot for the spread of dengue fever is a growing concern.
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In 2024, the Olympics bring excitement to France, as it prepares to welcome over 10 million athletes, spectators, officials, and tourists. The French government is all too aware of the risk of dengue fever lurking in the shadows. They are checking numerous sites regularly for mosquitoes carrying the disease. Could this be enough?
The super-spreader concept in infection epidemiology has been around for a while. Essentially, it means a small group of individuals, possibly just one person, is responsible for the majority of cases. Mary Mallon, a historical super-spreader, was an asymptomatic carrier of typhoid who may have infected over a hundred people.
In the case of COVID-19, a study in Hunan Province, China, revealed 15% of people caused 85% of the cases. When it comes to dengue, a study in Peru found 8% of human-occupied spaces accounted for more than half of the cases (it's important to note that dengue cannot be transmitted directly between humans; it's the dengue-carrying mosquito bites that spread the virus).
This isn't the first time the Olympics have concerned health experts due to virus transmission. Brazil's 2016 Olympics almost didn't happen because of Zika, another virus spread by the same mosquito. There were no reported cases, though.
Fears about COVID-19 at the Tokyo Olympics prompted drastic measures to minimize transmission. Although few infections occurred inside the Olympic "bubble," there was a moderate increase in cases among the general population.
What sets Paris apart?
The Aedes mosquito has expanded its reach significantly since 2016, and the global number of dengue cases skyrocketed since then. In 2016, there were 5.2 million reported cases worldwide. Halfway through 2024, that number has doubled to 7.6 million.
During the 2016 Olympics, over 200 countries are expected to send delegates to France. Many of those nations are experiencing dengue fever this year.
For the Paris Olympics to become a super-spreader event, multiple factors must align. There must be an adequate number of mosquitoes, a sufficient number of infected individuals, enough time, and a sufficient number of mosquito bites.
Thriving in Paris
The tiger mosquito has effortlessly adapted to urban Paris. It requires only the tiniest drop of water in a tiny container to lay its eggs. Preferring human blood, it strikes at dawn and dusk. The eggs can also withstand dry conditions for months, ready to hatch once re-wetted.
What's potentially concerning is that some of these mosquitoes may already be infected with dengue, likely through their mothers. This could considerably lower the number of bites needed to ignite an outbreak.
Within the Olympic timeline, an infected individual could be bitten by a mosquito and set off an epidemic within a week or so. A single female mosquito can lay up to 200 eggs at a time.
Most dengue cases are symptomless, so people may not even realize they have the virus. Those infected before or during the Olympics might not know they're carrying the virus. They could unknowingly spread the infection while traveling back home, potentially sparking an epidemic there.
Whether someone falls ill or not, they can still transmit the virus if bitten by an Aedes mosquito.
The recent dengue outbreak during Rio Carnival serves as a warning, though the event didn't get canceled.
Paris Olympics visitors, athletes, workers, volunteers, and even passersby are unknowingly participating in a massive, real-life experiment. Whether they realize it or not, they're all at risk.
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The risk of a single super-spreader, potentially an infected individual who is unaware they carry the virus, igniting an outbreak during the Paris Olympics is a concern. Given that the tiger mosquito, capable of carrying dengue, has thrived in urban Paris and can lay hundreds of eggs, the conditions for a potential super-spreader event might be present.
