Summary of the Key Points
This article uses the case of writer Chen Lanye contracting an adenovirus while swimming in the wild as a starting point to educate readers about the potential health risks associated with swimming, particularly the spread of adenoviruses through water. It compares the risks between public swimming pools and outdoor waters and provides practical advice on choosing safe swimming locations as well as self-protection methods. The main message is to remind everyone that while swimming is enjoyable, safety comes first; wild swimming carries extremely high risks, and even in public swimming pools, it’s important to choose clean ones.
1. Adenoviruses: The “Hidden Killers” Hidden in Water
Adenoviruses are not a single virus but belong to a large family with 7 subtypes and 57 serotypes. They can be spread through various means, such as droplets or by touching contaminated towels. However, the most overlooked route of transmission is through water—swimming pools that are not properly disinfected or outdoor waters that have not been treated can allow these viruses to thrive.
What are the symptoms of an infection? The typical condition is “pharyngoconjunctival fever,” also known as “swimming pool fever,” which includes fever, a sore throat, and red eyes. For example, 22 members of the swimming team from a sports school in Fujian were infected collectively, and nearly 90 people in Conghua, Guangdong, got sick within a week. The cause was insufficient residual chlorine levels in the pools (below 0.2mg/L), which failed to kill the adenoviruses; the athletes had inhaled contaminated water while swimming.
2. Public Swimming Pools vs. Outdoor Waters: What Are the Differences in Risk?
The risks in public swimming pools are “controllable” as long as proper disinfection is carried out (with residual chlorine levels between 0.3-0.5mg/L) and there is strict hygiene supervision. However, outdoor waters are much more unpredictable:
- The detection rate of adenoviruses is extremely high: Studies in 2024 showed that adenoviruses were found in 59.2% of all types of water bodies globally (rivers, lakes, groundwater), with some rivers having almost every sample contaminated.
- There are no disinfection measures in place, so you simply don’t know what’s lurking in the water. Therefore, the safest option is to avoid swimming in the wild!
3. What Other Hidden Risks Are There When Swimming?
Adenoviruses are just the tip of the iceberg:
- In public swimming pools, insufficient disinfection can lead to conditions such as conjunctivitis, otitis media, diarrhea (e.g., due to Cryptosporidium), and even amoebic meningitis (a 6-year-old child in Sichuan died from this in 2024 because the pool had too little chlorine).
- In outdoor waters, the risks are even greater and more fatal: schistosomes (can penetrate the skin after just 10 seconds of contact, leading to liver cirrhosis), Vibrio vulnificus (infections may result in amputation), leptospirosis (fever, jaundice), and hepatitis A. Schistosomes are particularly a concern; there are 170,000 hectares of snail-infested areas south of the Yangtze River, with a high incidence rate from April to October.
4. How to Choose a “Clean” Public Swimming Pool?
Follow these three tips:
1. Check the water: It should be clear and odorless. If the water is murky, green (indicating algae growth), or has a strong chlorine smell (too much chlorine or poor disinfection), leave immediately.
2. Review the reports: Swimming pools must display water quality test results, with free residual chlorine levels between 0.3-0.5mg/L (higher requirements for children’s pools).
3. Inspect the facilities: Are there mandatory foot-soaking areas (at least 2 meters long and 20 cm deep)? Are the changing rooms and showers clean and odor-free? These are essential safety standards.
5. What If You Want to Swim in the Wild?
If you insist on swimming in natural waters, only choose officially designated swimming areas and pay attention to the following:
- Check the water quality reports: The Ministry of Ecology and Environment releases weekly reports on seawater bathing area quality from June to September; choose areas with “excellent” or “good” ratings.
- Pay attention to warnings: Do not enter the water if the beach is closed due to pathogen levels exceeding safe limits, heavy winds and waves, or after heavy rain (which can cause sewage overflow), or if there’s algal blooms (green or blue water with a fishy smell).
- Avoid schistosome-infested areas: Beaches and paddy fields in 12 provinces south of the Yangtze River are particularly at risk; avoid playing in the water or doing laundry there.
Finally: No Matter Where You Swim, Develop These Habits
Always follow these safety practices:
- Take showers before and after swimming: Rinse off sweat and grease before entering the pool to prevent depleting its chlorine levels, and wash off any pathogens and disinfection residues afterward.
- Wear goggles and a swim cap: Goggles protect against conjunctivitis, and a swim cap protects your hair and prevents hair from clogging the filter.
- Do not swim if you are sick: Avoid swimming if you have diarrhea (especially due to Cryptosporidium) or skin wounds/infected illnesses; do not contaminate the water and avoid harming others.
- Do not swallow water: Do not drink pool water, and especially avoid drinking water from outdoor streams, as it may contain animal waste or dead animals.
In summary, swimming is a great exercise, but safety is more important than enjoying the coolness. Don’t risk your health!