The 2026 flood situation and why this matters now

According to a Dailynews report citing Thailand's Department of Disaster Prevention and Mitigation (DDPM) at 06:00 on 5 October 2026, floods were affecting 26 provinces plus Bangkok, with 1,270,151 households affected in total (source: dailynews.co.th). Huge numbers of buildings are being cleaned with household products: the right first step, but not the last.

Floodwater carries sewage, septic overflow and farm soil. Some germs wash off easily; others resist soap, burrow into materials or hide in pipe slime.

Example case: three days of scrubbing, and the smell still came back every morning

Note: this is a typical scenario compiled from common post-flood situations, not the account of any specific customer.

Nok, a meticulous homemaker in a two-storey row house in Bang Bua Thong, Nonthaburi, spent three full days after knee-deep water receded scrubbing her ground floor. Dish soap mixed with laundry powder went on tiles, walls, table legs and the kitchen cabinet, followed by a lemon-scented floor cleaner. Everything looked spotless.

Yet every morning the damp, musty smell returned. Her five-year-old son developed loose stools, and her husband an ankle rash. Nok took her son to a doctor, as anyone should. A closer look found black dots on the gypsum behind the fridge, dark grout, a slimy drain and one damp sponge used for the whole house.

Soap and household cleaners are designed to remove dirt, not to deal with every germ on every surface.

Soap, cleaners and disinfectants are not the same thing

Soap loosens grime so water carries it away; many germs are washed off rather than destroyed. Enveloped viruses, which are wrapped in a fatty outer layer, such as influenza, RSV and coronaviruses, are fairly well disrupted by soap.

But germs are not built alike. Non-enveloped viruses, bacteria with tough cell walls, bacterial spores and fungal threads inside materials resist soap far better. Mud also shields germs and weakens many disinfectants, porous materials and pipe biofilm keep liquids out, disinfectants need proper contact time, and one sponge used everywhere simply moves germs around.

This is why the US Centers for Disease Control and Prevention (CDC) and WHO give flood-affected homes the same core message: clean first, then disinfect, and dry everything as quickly as possible to limit mold.

How we ranked the flood germs hardest to remove with soap

This is an editorial ranking by the World Health Disinfection (WHD) team. It is not an official ranking and is not based on case statistics. We weighed these criteria together:

1. Structural toughness: no fatty envelope, an unusually tough cell wall, or a spore form, based on general microbiology.
2. Ability to hide in porous materials, biofilm, narrow gaps or water systems that brushes and soap cannot reach.
3. Link to floods in guidance from WHO, CDC and Thailand's Department of Disease Control.
4. Severity and at-risk groups such as young children, older adults, pregnant women and people with chronic illness.
5. How easily it spreads through hands, surfaces, food, water or airborne droplets.

We avoid percentages and survival times, which vary with conditions; persistence is described qualitatively. Ask WHD for organism-specific test data.

The ranking: 10 flood germs hardest to remove with ordinary soap and cleaners

From hardest to easiest for household cleaning. A lower position does not mean safe.

No. 1: Bacterial spores in mud, such as the tetanus germ (Clostridium tetani)

Why it ranks here: Bacterial spores are among the toughest life forms in nature. They tolerate drying, a fair amount of heat and most everyday chemicals better than anything else on this list. Soap does not destroy them, and most surface disinfectants are not designed for them. Floods spread spore-carrying soil through homes.

Where it hides: thin layers of dried mud on floors, under door thresholds and cabinets, inside rubber boots and gloves used for mud removal, and on debris such as wood, nails and scrap metal sheets.

Symptoms and who is at risk: the risk comes from wounds, not from touching surfaces, especially puncture wounds from nails, deep cuts or wounds contaminated with soil. Tetanus causes muscle stiffness and a locked jaw and needs emergency hospital care.

Prevention: boots and heavy gloves, wash wounds at once, ask a doctor about tetanus vaccination.

What cleaning and spraying can do: the real answer for spores is to get the mud out. WHD spraying follows mud removal and targets bacteria, viruses and fungi on surfaces; we do not claim it destroys spores.

No. 2: Mold rooted in porous materials, such as Stachybotrys and Aspergillus

Why it ranks here: mold does not sit only on the surface. It sends threads into the material itself, so scrubbing with soap removes only the visible part. CDC notes that mold can begin to grow within 24 to 48 hours after materials get wet, and the slower a building dries, the deeper it roots. Stachybotrys favours gypsum paper facing; Aspergillus releases airborne spores easily.

Where it hides: lower sections of gypsum walls, behind fridges and wardrobes, under laminate flooring, in wooden door frames, ceilings, mattresses, carpets and cardboard.

Symptoms and who is at risk: stuffy nose, coughing, sneezing, itchy eyes, rashes and asthma flare-ups. People with allergies or asthma, older adults, young children and anyone with weakened immunity should stay out of heavily affected rooms.

Prevention: dry fast with fans and dehumidifiers; remove soaked porous items and wet gypsum, wearing a mask.

What cleaning and spraying can do: spraying cannot replace removing deeply moldy material. After removal and cleaning, however, spraying helps deal with remaining spores and mold on wall frames, floors and nearby hard surfaces. According to product information, CHEMGENE HLD4H covers fungi in general. For a specific species such as Stachybotrys or Aspergillus, ask WHD for the test data.

No. 3: Norovirus

Why it ranks here: norovirus has no fatty envelope, so it stands up to soap, alcohol gel and general cleaners much better than cold viruses do. It spreads readily through hands, surfaces, food and water contaminated by faeces or vomit. CDC notes symptoms usually begin 12 to 48 hours after exposure.

Where it hides: toilets, taps, door handles, stair rails, kitchen counters, chopping boards, dishes rinsed in unsafe water, and anywhere someone has vomited.

Symptoms and who is at risk: nausea, vomiting, diarrhoea, stomach cramps and sometimes a low fever. Young children and older adults can become dehydrated quickly and should see a doctor if they cannot keep fluids down.

Prevention: wash hands with soap and clean water for at least 20 seconds, which works better than alcohol gel alone for this virus, and clean up vomit promptly.

What cleaning and spraying can do: norovirus is on the list of organisms that CHEMGENE HLD4H product information states it covers. Spraying after cleaning therefore treats shared touch points throughout a room rather than only the spots someone remembered to wipe.

No. 4: Hepatitis A virus

Why it ranks here: like norovirus, hepatitis A is non-enveloped, tolerates the environment and ordinary cleaners well, and spreads through food and water contaminated with faeces, a real possibility when floods overwhelm septic tanks and water supplies. Its incubation period is long; CDC gives a typical range of 15 to 50 days, so people may pass it on before they know they are infected.

Where it hides: utensils, chopping boards, water tanks and bathroom surfaces.

Symptoms and who is at risk: tiredness, loss of appetite, nausea, pain in the upper right abdomen, yellow skin or eyes and dark urine.

Prevention: drink boiled or bottled water, eat freshly cooked food, wash hands before preparing food, and ask a doctor about vaccination if you are in a risk group.

What cleaning and spraying can do: hepatitis A is not named on WHD's pages, but it belongs to the virus group the product says it covers. Ask WHD if you need organism-specific test data.

No. 5: Pseudomonas aeruginosa biofilm in pipes and drains

Why it ranks here: Pseudomonas loves moisture and is very good at building biofilm, a slimy coating that wraps bacteria in a layer liquids struggle to penetrate. Pouring cleaner down a drain rarely reaches the deeper layers.

Where it hides: drains, sink pipes, shower heads, AC drip trays and wet sponges.

Symptoms and who is at risk: healthy people seldom become seriously ill, but it can infect wounds, skin, ears and eyes and is a concern for people with weakened immunity, open wounds, or bedridden patients using medical devices.

Prevention: scrub drains and remove drain covers to clean them, replace sponges and cloths that touched floodwater, run water through pipes before use, and clean AC drip trays.

What cleaning and spraying can do: biofilm must be broken up mechanically first; then the surfaces around drains, basins and bathroom floors can be disinfected. Pseudomonas belongs to the bacteria group the product says it covers; specific test data is available on request.

No. 6: Environmental mycobacteria (nontuberculous mycobacteria)

Why it ranks here: mycobacteria have a waxy cell wall that resists many chemicals better than ordinary bacteria. They live naturally in soil and water and can settle in plumbing.

Where it hides: mud, shower heads, water pipes, storage tanks and constantly damp surfaces.

Symptoms and who is at risk: most people never become ill, but those with chronic lung disease, older adults and people with weakened immunity can develop lung or skin infections. See a doctor for a persistent cough or a wound that will not heal.

Prevention: remove and clean shower heads, empty and wash water tanks before reuse, and keep wounds covered during clean-up.

What cleaning and spraying can do: mycobacteria are one of the groups named in CHEMGENE HLD4H product information, which signals a stronger product than ordinary floor cleaners. Surface spraying does not replace cleaning water tanks or plumbing.

No. 7: Rotavirus and adenovirus

Why it ranks here: both are non-enveloped and therefore fairly resistant to soap and general cleaners. Rotavirus is a major cause of diarrhoea in young children, while adenovirus causes anything from red eyes and sore throat to diarrhoea. Both spread easily in crowded post-flood housing.

Where it hides: toys, bottles and teats, changing tables, shared towels and handkerchiefs, TV remotes and pillows.

Symptoms and who is at risk: watery diarrhoea, vomiting, fever, red and watery eyes, sore throat. Young children dehydrate quickly; seek medical care if a child is drowsy, passes little urine or cannot drink.

Prevention: give everyone their own towel, wash washable toys, discard soft toys soaked by floodwater, boil or steam bottles, and ask a doctor about rotavirus vaccination for infants.

What cleaning and spraying can do: both belong to the virus group the product says it covers, though neither is named on WHD's pages; ask for organism-specific data.

No. 8: Enteroviruses that cause hand, foot and mouth disease

Why it ranks here: also non-enveloped, so they last a while on surfaces and do not come off easily with plain water. Hand, foot and mouth disease is common among young children in Thailand during the rainy season and spreads through saliva, nasal discharge, blister fluid and stools.

Where it hides: toys, crawling mats, small chairs and handrails.

Symptoms and who is at risk: fever, mouth sores, and blisters on hands, feet and buttocks. Children under five are the main risk group. See a doctor at once for high fever, drowsiness, frequent vomiting or any neurological symptoms.

Prevention: keep sick children home as a doctor advises, wash hands after every nappy change, separate utensils and clean toys daily.

What cleaning and spraying can do: hand, foot and mouth virus is named on WHD's disinfection service page, according to the service information, making spraying a good fit for homes with toddlers, childcare centres and kindergartens recovering from floods.

No. 9: Legionella pneumophila in water systems and cooling towers

Why it ranks here: Legionella does not live on surfaces you can scrub. It grows in warm, stagnant water with biofilm: storage tanks, unused water heaters and building cooling towers. Soap and floor cleaner play no role at all. The main risk is in large buildings.

Where it hides: rooftop tanks, pipes left unused during the flood, shower heads in rooms closed for a long time.

Symptoms and who is at risk: it is caught by breathing in contaminated water droplets and causes pneumonia-like illness with fever, cough and breathlessness. Older adults, smokers and people with lung or chronic disease are at higher risk.

Prevention: flush every outlet before reopening a building, clean water tanks, and have water-system specialists inspect cooling towers according to building standards.

What cleaning and spraying can do: surface spraying is not a water-system treatment, so we recommend handling plumbing separately. Spraying covers bathroom, guest-room and common-area surfaces the flood reached.

No. 10: Sewage bacteria hiding under mud film, such as E. coli and Salmonella

Why it ranks here: these bacteria are not especially tough. Exposed directly to a suitable disinfectant, they are not hard to control. After a flood, though, they are often wrapped in mud, grease and septic waste, which stops soap and ordinary cleaners from working fully.

Where it hides: grout lines, room corners, skirting boards, under sinks, kitchen cabinets, counters, fridges that lost power, and bathroom floors where septic tanks overflowed.

Symptoms and who is at risk: diarrhoea, stomach pain, nausea and fever; some E. coli types cause bloody diarrhoea. Young children, older adults, pregnant women and people with weakened immunity should see a doctor early.

Prevention: throw away food that touched floodwater or sat in a fridge without power for a long time, scrape mud out of grooves and corners, wash with detergent and clean water, then let everything dry.

What cleaning and spraying can do: Salmonella is named in the product information; E. coli belongs to the general bacteria group the product says it covers. Once mud is gone, spraying lets the disinfectant reach every surface in the room, including corners hands cannot reach.

Why soap, floor cleaner or bleach alone falls short after a flood

• Chlorine bleach is used up by organic matter. Poured on muddy floors, most of its strength is spent on the mud before it reaches germs.
• Never mix bleach with other products. Combining it with ammonia or acidic cleaners releases dangerous gases, a hazard CDC warns about clearly.
• Wiping is never complete. Under beds, behind cabinets, upper walls and furniture crevices are routinely missed.
• Bleach does not fix mold inside porous materials. CDC and EPA advise removing damaged porous materials instead.

Soap and bleach are useful cleaning-stage tools. Whole-space disinfection needs a purpose-made product, even application and correct contact time.

WHD post-flood disinfection spraying: the finishing step after cleaning

World Health Disinfection provides a disinfection spraying service by trained technicians. According to the service information, technicians use spraying and/or ULV (Ultra Low Volume) fine-mist fogging so the disinfectant reaches surfaces evenly. The product is CHEMGENE HLD4H, a medical-grade disinfectant from the United Kingdom containing Benzalkonium Chloride and Didecyldimethylammonium Chloride.

The service and product pages describe it as broad-spectrum against viruses, bacteria and fungi, naming organisms including SARS-CoV-2 (COVID-19), Human Coronavirus 229E, RSV, influenza H1N1 and H5N1, HIV, norovirus, hand, foot and mouth virus, vaccinia virus, mycobacteria, Salmonella and Bordetella pertussis. The service page states 99.99% efficacy and the product page states 99.85% against COVID-19 within one minute. The service page also cites the Department of Medical Sciences, Mahidol University, NHS England and EN 14476:2013+A2:2019. For organisms outside this list, please ask for test data before deciding.

Five service steps

1. Survey: the team checks the old water line, materials, mold spots, septic overflow areas and who lives there.
2. Mud removal and washing first: spraying happens only after mud is removed, surfaces are washed and damaged materials are taken out.
3. Zoning and preparation: people and pets leave the zone being sprayed; food, utensils and personal items are put away.
4. Spraying: floors, walls, furniture, touch points, bathrooms, kitchens and hidden corners are treated.
5. Re-entry: according to the service information, wait about 30 minutes before normal use, always following the re-entry time the technicians give on site.

We do not claim spraying leaves no residue. Ask the technicians about food-contact surfaces or toddler areas at any stage, and anyone who feels unwell should see a doctor; spraying is not medical treatment. For lingering musty air, consider the complementary residential ozone disinfection service. The service includes a free CHEMGENE spray bottle and WELLGIENIC wet tissues, and a tax invoice is available.

10 reasons to spray after cleaning when soap-resistant germs are involved

1. Reaches what hands cannot: ULV mist gets behind cabinets and under furniture.
2. Made to disinfect, not just to lift dirt like soap.
3. Several germ groups in one visit: viruses, bacteria and fungi, per the disinfection service information.
4. Tough organisms named: norovirus and mycobacteria appear in the product information.
5. No risky product mixing, because technicians use one product to a standard routine.
6. Saves effort: no more daily re-scrubbing without knowing whether it works.
7. Suits vulnerable households with babies, older adults or bedridden patients.
8. Expert on-site assessment of what to remove or re-wash before spraying.
9. Quick return: about 30 minutes after spraying, per the service information.
10. Confidence for customers and staff when shops, offices and schools reopen. See the service.

Before and after spraying

Example case: a front-room noodle shop that needed to reopen fast

Note: an illustrative example to explain the process, not a real customer review.

Ek runs a noodle shop on his shophouse ground floor, flooded for about a week. Afterwards he and his wife washed the shop with detergent and bleach, but sewage had backed up through the rear drain and the wooden cabinet under the counter was growing green spots. The team advised removing the swollen cabinet, scrubbing the drain and scraping the grout, then zoned and sprayed the shop while the family waited outside. After the re-entry time, they rinsed utensils in clean water before cooking.

Checklist before and after spraying

• Wear boots, heavy gloves and a mask; remove all mud and scrape grout and corners.
• Discard food and medicine that touched floodwater.
• Remove soaked or moldy gypsum, mattresses and carpets.
• Scrub drains, replace every sponge and cloth.
• Dry the building fast with ventilation, fans and dehumidifiers.
• Wash wounds immediately and ask a doctor about tetanus vaccination.
• After spraying: re-enter on time, rinse food-contact surfaces, check old mold spots weekly, and see a doctor for fever, diarrhoea, calf pain, jaundice or infected wounds.

FAQ

If soap works for hands, why not for houses?
Handwashing works because you rub every part and rinse at once. Houses have porous materials, pipes and large areas that cannot be rubbed evenly.

If I spray, can I keep the moldy wall?
No. Deeply moldy porous material should come out; spraying follows removal and cleaning.

Does CHEMGENE HLD4H destroy tetanus spores?
We make no such claim. Remove the mud, care for wounds and talk to a doctor about vaccination.

What should families with babies do?
Remove bottles, toys and nappies from the zone, take the baby elsewhere during spraying, return on time and rinse baby items first.

Should a restaurant spray before or after washing dishes?
Move dishes out, spray the space, then wash dishes and prep surfaces with clean water before service.

Finished scrubbing? Let WHD handle what soap cannot

On-site assessment and post-flood spraying for homes, shops and offices.

See the WHD Disinfection Service

Call 065-556-6294 | LINE @whd268

Related services and references

• WHD disinfection spraying service
• Residential ozone disinfection
• Dailynews, flood update citing DDPM, 5 Oct 2026: https://www.dailynews.co.th/news/6249374/
• CDC, Floods: https://www.cdc.gov/floods/
• CDC, Norovirus: https://www.cdc.gov/norovirus/
• WHO fact sheets: https://www.who.int/news-room/fact-sheets
• Department of Disease Control, Thailand: https://ddc.moph.go.th/