The True Story: More Than Half Tested Positive

On 4 December 2025, the Chinese Center for Disease Control and Prevention (China CDC) released data for the week beginning 24 November showing 51.1% of outpatient flu-like illness visits tested positive for influenza, up from 44.8% the week before.

Positivity was markedly higher among children aged 5–14, and flu clusters in schools increased. China CDC advised stronger monitoring in nurseries, elderly care homes and schools.

The Key Lesson: School-Age Children Are Hit Hardest, and Gather in the Same Places After School

Swim schools and community or mall pools take children from many schools in the evenings and at weekends. Points to watch are:

• Changing rooms and showers damp and used in turn
• Lockers and benches many children use
• Kickboards and training aids passed around every class
• Towels piled together on poolside chairs
• Parents waiting in closed air-conditioned rooms

How Flu Spreads

According to the World Health Organization, seasonal influenza spreads easily where people gather, such as schools and nursing homes. It spreads through droplets when people cough or sneeze, and through hands that touch contaminated surfaces and then the eyes, nose or mouth. Most people recover within a week, but young children, older adults, pregnant women and people with chronic illness are at risk of severe disease. Influenza is an enveloped virus, which suitable disinfectants can inactivate.

Risk Register for Swim Schools and Pools

1. Children with fever still attend: likelihood high / impact high / level critical. Mitigation: allow rescheduling when ill and screen at entry. Owner: swim school manager
2. Damp changing rooms: likelihood high / impact medium / level high. Mitigation: clean several times a day and ozone-treat on a schedule. Owner: facilities team
3. Training aids not wiped: likelihood high / impact low / level medium. Mitigation: rinse and wipe after class. Owner: swim coach
4. Towels piled together: likelihood medium / impact low / level low. Mitigation: personal towels and bags. Owner: swim coach
5. Closed parents' waiting room: likelihood medium / impact medium / level medium. Mitigation: ventilate and fog on a schedule. Owner: manager

Ways to Reduce Flu Risk in Swim Schools

1. Allow rescheduling when children are ill
2. Check for fever at the entrance
3. Use personal towels and bags for everyone
4. Rinse training aids after class
5. Clean changing rooms several times a day
6. Ventilate the parents' waiting room
7. Fog and ozone-treat changing and locker rooms

How ULV Disinfection Fogging Helps

The World Health Disinfection disinfection service uses ULV fogging machines that turn the disinfectant into a fine mist. It settles across the whole area, including corners, curtains, upholstery and surfaces that hand wiping cannot reach.

• Whole-area coverage without relying on wiping spot by spot
• Quick return to use, typically about 30 minutes after fogging
• Uses Chemgene HLD4H, which meets EN 14476 for virucidal activity according to the product page
• The team wears full protective equipment, so owners and staff do not take the risk themselves
• Report and photos after the job for customers, management or authorities
• Tax invoice with 3% withholding tax for companies and agencies

Ozone Treatment for Closed Rooms and Stuffy Spaces

The World Health Disinfection ozone treatment service uses machines that generate ozone gas from oxygen in the air. It suits closed rooms such as meeting rooms, bedrooms, classrooms, sick bays and vans, helping reduce germs in the air and on surfaces and removing stale odours. Ozone breaks back down into oxygen after treatment, leaving no residue.

• Works alongside disinfection fogging: spray or wipe surfaces first, then use ozone for the air and corners of closed rooms
• No people or pets in the room during treatment: the team seals the room and runs a timer
• Ventilate after treatment before normal use resumes
• Machines tested by Intertek, according to WHD's service page
• Ideal after someone has been ill, such as recovered patients' rooms, shared bedrooms and shuttle vans

Before and After

Frequently Asked Questions

Q: Does pool chlorine kill flu? A: Properly maintained pool water is low risk, but flu spreads through droplets and surfaces in changing and waiting rooms, which need separate cleaning.

Q: Which children had the most flu in China? A: China CDC said children aged 5–14 had markedly higher positivity than other groups.

Q: Does the fogging disinfectant work on flu? A: The team uses Chemgene HLD4H, which meets EN 14476 for virucidal activity according to the product page, and influenza is an enveloped virus that suitable disinfectants can inactivate. Fogging does not replace vaccination or handwashing.

Q: Can I enter the room right after ozone treatment? A: No one should be in the room during treatment. Ventilate afterwards before normal use; the team will advise the right time for the room size.

Q: Can swim schools or clubs get a tax invoice? A: Yes. Tax invoices are issued and 3% withholding tax is supported. Call 065-556-6294 or LINE @whd268.

Related Links and Sources

• World Health Disinfection disinfection service
• World Health Disinfection ozone treatment service
• Chemgene HLD4H disinfectant and price
• Influenza information from Thailand's Department of Disease Control, hotline 1422
• WHO seasonal influenza fact sheet

Prevent Flu with Disinfection Fogging and Ozone Treatment

The true story from China shows school-age children are hit hardest. Swim schools that care for changing rooms and equipment let children learn to swim safely. Reduce the risk with the World Health Disinfection disinfection service for waiting rooms, pool decks and restrooms, and the ozone treatment service for changing rooms and locker rooms. To book, call 065-556-6294 or LINE @whd268.

Call 065-556-6294 | LINE: @whd268