Triathlon athletes dive into the Seine with the Eiffel Tower in the background during a test … (+)
Last week, Paris Mayor Anna Hidalgo and other elected officials swam in the Seine to reassure Olympic competitors and spectators that the river is safe and that the pollution has been cleaned up. With so much talk about the dangers of swimming in the Seine, it’s a good time to raise other health risks with the crowds of visitors heading to Paris.
Dengue
Dengue and other arbovirus infections are of particular concern. Last September, several people who had never travelled contracted dengue in Paris. This demonstrated for the first time that dengue can be transmitted locally in northern Europe. Dengue cases have been steadily increasing worldwide, from 5.2 million cases in 2016 to nearly 10.5 million. million in the Americas in 2024.
Dengue fever is transmitted by Aedes albopictusThe tiger mosquito, which feeds on humans, is particularly problematic because it needs very little water (e.g. a bottle cap) to lay its eggs, which can resist drying out for months. In particular, the dengue virus can be transmitted from the mother mosquito to her eggs. When it rains again, the eggs are resurrected and hatch, triggering a new cycle of reproduction and infection.
Many athletes will arrive in France from countries where arbovirus infections (dengue, chikungunya, zika) and malaria are endemic. Almost all cases of malaria were imported into France (2,783 in 2022); seven were contracted in the EU.
Covid and flu
According to the World Health Organization, influenza activity is high, with the A(H3N2) virus in South America and the A(H1N1) virus in Africa and Oceania.
The number of new weekly Covid cases is high, particularly in the UK, Portugal and Greece, Europe and China, Thailand and New Zealand. SARS-CoV-2 levels in wastewater are rising again in much of the US. Mike Hoerger, PhD, Covid forecaster, notes that current transmission is >3x higher than typical for this time of year.
Belgian Remco Evenepoel of Soudal Quick-Step pictured wearing a face mask at the start of stage 15 … (+)
Many Olympic and Tour de France athletes wear masks to protect themselves from infection after years of training for the events. For the Belgian team, masks will be mandatory. Five of the 176 Tour riders have dropped out due to Covid infections. Two Swiss Olympic mountain bikers have already withdrawn due to illness, as have British athletes Holly Bradshaw and Sarah McDonald.
The Olympics are expected to attract 15 million visitors, including 2 million from outside the region. Given the experience of Taylor Swift concerts, which were apparently highly contagious events, one might expect a Covid outbreak to occur in such crowded venues. Covid can also be transmitted outdoors, in crowded conditions.
The quality of the water of the Seine
The Seine has been off-limits to swimming for over 100 years due to pollution. Historically, excess rainwater from sewer pipes mixes with rainwater and is dumped directly into the river after heavy rains. Massive efforts to clean up the pollution have been undertaken, including the construction of a vast rainwater storage facility, capable of holding the equivalent of 20 Olympic-sized swimming pools. This has cost at least $1.55 billion.
This week, to reassure people that the Seine was safe, Mayor Anna Hidalgo and others went swimming in the river. They felt “safe” because E. coli levels had dropped significantly on Tuesday, after a spike the previous Friday due to heavy rain. The reported levels were below the World Triathlon Federation’s limit of 1,000 CFU/100 ml.
French officials should not be so reassured by these numbers. Fluidion, a water intelligence company based in Paris and Los Angeles, has tested the Seine and made its data freely available. Fluidion uses new technology that can provide additional information about water quality, such as measuring the number of “free” (or planktonic) E. coli bacteria and the total E. coli count, which includes bacteria aggregated with particles of stool and other wastewater.
Dan Angelescu, Fluidion’s founder and CEO, explained via email that standard microbiological laboratory methods were designed for water containing only “free” E. coli bacteria and are therefore blind to E. coli aggregates.
Data courtesy of Fluidion Open Data Initiative – … (+)
From this graph, we can see that what is most worrying is the “overall” level of E. coli. These levels (the red triangles) are often higher than the thresholds approved by the World Triathlon Federation. The technique used by the authorities may seriously underestimate the risk. The red triangles of the “overall” level of E. coli could provide a more accurate representation of the real risk.
Although the weather gods appear to be in Paris’ favor with high temperatures of just 80 degrees and little rain during the Olympics, other concerns remain.
Water quality has been an issue at other Olympic Games. For example, the 2016 Olympic Games in Brazil were concerned about “Rio Sewercide” and the risk of athletes contracting multidrug-resistant (MDR) infections from dirty water.
Leptospirosis The infection remains a concern because very few bacteria are needed to cause this infection. All freshwater sports enthusiasts are exposed to this infection, which is transmitted through the urine of infected animals that contaminate the water. Rodents are often the source. Outbreaks have occurred after flooding and whitewater rafting. Symptoms include headache, fever, muscle aches and redness of the conjunctiva.
Heat stroke, air pollution and other infections
Paris is ranked as the fourth deadliest European city for air pollution by the Lancet Planetary Health magazine. The influx of tourists is likely to worsen this year, causing respiratory problems and widespread illness.
Air pollution also risks worsening heat problems for visitors. Authorities are warning the public and staff about the risk of heatstroke. Asthma and COPD are also worsened by poor air quality.
Foodborne infections (e.g. Listeria or Salmonella) and gastrointestinal bacteria such as norovirus should be expected.
Whooping cough (whooping cough) is experiencing a resurgence in Europe. European Centre for Disease Prevention and Control In 2023, 25,130 cases of whooping cough were recorded, compared to 32,037 cases between January 1 and March 31, 2024 alone. More than 5,800 cases were recorded in France during these three months. This infection, called the 100-day cough, is transmitted by droplets projected when a person coughs or sneezes and is highly contagious. It is a vaccine-preventable disease, and currently, vaccination is recommended with the Tdap vaccine (tetanus and pertussis vaccine) every ten years to boost immunity against both.
Finally, with lower vaccination rates, measles Measles is on the rise in many countries. In the first three months of 2024 alone, 56,634 cases of measles and four deaths were reported in Europe. Measles is highly contagious, infecting 90% of those exposed. It is not a mild childhood infection: measles can cause pneumonia, encephalitis and death.
According to the latest forecasts, around 11.5 million tourists will travel to Paris for the Olympic Games. I prefer to watch them from my home, in peace.