A Typical Scenario: A Curry-Rice Shop Desperate to Reopen

This example case is a composite of situations commonly seen after floods, not a review from a specific customer. Auntie Daeng has run a small curry-on-rice shop in front of a market in a district of Phra Nakhon Si Ayutthaya for almost twenty years. Waist-high water filled the shop, the chest freezer lost power for days, and pots, steel trays and wooden chopping boards floated in murky water that had come up from drains and nearby septic tanks.

As soon as the water receded, she shovelled out the mud, hosed the floor with newly restored tap water, scrubbed the pots with dishwashing liquid and planned to reopen within three days, because regulars had just returned home with no working kitchens. Her son, who trained in public health, warned her that a restaurant after a flood is where germs from sewage can reach dozens of plates in a single lunchtime. One missed spot, such as a soaked chopping board, a table cloth or ice from a flooded bin, could make many customers ill at once and undo years of reputation in a week.

That warning made her stop and ask which germs cause diarrhoea, where they hide, and what else she should do before reopening with confidence. Those questions shaped this ranking.

The 2026 Floods and the Risk of Diarrhoea and Food Poisoning

According to a Daily News report citing Thailand's Department of Disaster Prevention and Mitigation (DDPM) at 06:00 on 5 October 2026, floods affected 26 provinces plus Bangkok, a total of 1,270,151 households. That includes home kitchens, restaurants, market stalls, school canteens and community kitchens that all need to start cooking again.

WHO and CDC advise treating floodwater as contaminated with sewage, discarding food that touched floodwater or sat in a fridge without power for too long, and cleaning surfaces before disinfecting them. Thailand's Department of Disease Control warns each flood season about acute diarrhoea, food poisoning and dysentery, which tend to rise when clean water and sanitation are disrupted.

How We Ranked Diarrhoea Germs After Floods (Editorial, Not Official)

This is an editorial ranking by the WHD team for education. It is not official data from any health authority and is not based on this year's case counts. We weighed:

1. Link to floods: how often the germ appears in WHO, CDC or Department of Disease Control guidance on floods, sewage and food.
2. Ease of spread: whether a small dose causes illness and whether it travels through hands, surfaces, water and food.
3. Severity and at-risk groups: especially young children, older adults, pregnant women and people with weak immunity.
4. Persistence: judged qualitatively, with no invented survival times.
5. Role of kitchen and bathroom surfaces: how much cleaning and surface disinfection can break the chain.

The list is a guide to what to watch first in homes and restaurants after a flood, not a statement that number one is the most common everywhere. Follow your provincial health office for local disease information.

How Diarrhoea Germs Travel from Sewage to Your Plate

Almost every germ on this list follows the faecal-oral route. It leaves the gut of a person or animal, enters sewage, septic tanks and drains, and during a flood it flows into homes and shops, settling on floors, walls, cupboards, chopping boards and anything that was submerged. From there it reaches the hands of whoever cleans up or handles items, and then the mouth through food, drinks or an unconscious touch.

A second route people overlook is food spoiled by power cuts. When a fridge stops for days, chilled food sits at temperatures where bacteria multiply, and some bacteria produce toxins that reheating does not fully destroy. That is why CDC's advice is simple: when in doubt, throw it out.

Diarrhoea Germs After Floods Ranked: The Top 10

No. 1: Norovirus

Why first: norovirus is a leading cause of acute diarrhoea and food poisoning worldwide. A tiny dose causes illness, it spreads through food, water, hands, surfaces and vomit droplets, and as a non-enveloped virus it is hardy. In a restaurant, one sick food handler can make many customers ill at once.

Where it hides: toilets, taps, fridge handles, ladles, prep tables, table cloths and anywhere someone vomited.

Symptoms and risk: sudden vomiting, watery diarrhoea, cramps and sometimes low fever. Young children and older adults risk dehydration; sip oral rehydration solution as health workers advise and see a doctor if very weak or passing little urine.

Prevention: people with diarrhoea or vomiting should not cook for others; wash hands with soap; clean vomit wearing gloves.

Cleaning and spraying: norovirus is listed as covered in CHEMGENE HLD4H product information (according to product information), so spraying bathrooms and prep areas after washing targets it directly.

No. 2: Pathogenic E. coli (Escherichia coli)

Why here: E. coli lives in human and animal intestines and is the classic indicator of faecal contamination. Most types are harmless, but some cause diarrhoea, some cause bloody diarrhoea, and in young children or older adults some can lead to kidney complications. In sewage-laden floodwater it is near the top of the list.

Where it hides: kitchen and bathroom floors reached by sewage, sinks, chopping boards, produce washed in dirty water and ice from flooded bins.

Symptoms and risk: loose stools and cramps, sometimes blood. Bloody stools, reduced urine, paleness or extreme tiredness need a doctor at once.

Prevention: discard ice, food and produce that touched floodwater, cook meat thoroughly, wash produce and dishes in safe water, and keep raw and cooked boards apart.

Cleaning and spraying: E. coli is not named on WHD's pages, so we make no organism-specific claim. It belongs to the bacteria group the product says it covers, and WHO and CDC advise cleaning then disinfecting flood-contaminated surfaces. Ask WHD for E. coli test data if needed.

No. 3: Salmonella

Why here: Salmonella is a textbook cause of food poisoning, carried in the guts of poultry, pets and other animals. Floodwater flowing through farms, pens and sewers can bring it in, and it multiplies in food left unrefrigerated by power cuts.

Where it hides: fridges without power, trays of chicken and eggs, raw-meat boards, sponges and prep tables.

Symptoms and risk: fever, cramps, diarrhoea, nausea and vomiting; young children, older adults and immunocompromised people may become seriously ill. See a doctor for high fever or persistent symptoms.

Prevention: discard food left unchilled too long, cook chicken and eggs well, wash hands after raw meat and replace flooded sponges.

Cleaning and spraying: Salmonella is listed as covered in product information (according to product information). Spraying kitchens and food stores after washing fits this risk; food-contact surfaces should be rinsed with clean water afterwards as technicians advise.

No. 4: Shigella, the Cause of Bacillary Dysentery

Why here: Shigella causes bacillary dysentery, needs only a small dose, and passes easily from person to person when sanitation is poor, so it thrives in crowded shelters or homes with unusable toilets.

Where it hides: shared toilets, door handles, water dippers, rails and carers' hands.

Symptoms and risk: fever, painful urges, frequent small stools that may contain mucus or blood. Young children are at high risk; see a doctor for bloody stools or high fever.

Prevention: wash hands after the toilet and nappy changes, do not share dippers and clean shared toilets often.

Cleaning and spraying: Shigella is not named on WHD's pages; it belongs to the bacteria group the product says it covers. Wash, then spray toilets and touch points, and ask WHD for specific data.

No. 5: Rotavirus

Why here: rotavirus is a major cause of severe diarrhoea in babies and toddlers, spreads by the faecal-oral route and persists reasonably well. Its rank reflects severity in children rather than adult food poisoning.

Where it hides: toys, bottles, formula equipment, changing tables and crawling areas.

Symptoms and risk: vomiting, watery stools and fever; toddlers dehydrate fast. A drowsy child with a dry mouth and little urine needs a doctor quickly. Ask your doctor about vaccination.

Prevention: prepare formula with boiled or bottled water, rinse bottles in clean water and wash hands after nappy changes.

Cleaning and spraying: rotavirus is not named on WHD's pages, so no tested claim; it belongs to the virus group the product says it covers. Ask WHD for details.

Ranks 6 to 10: Poultry Bacteria, Seafood, Toxins and Parasites

No. 6: Campylobacter

Why here: Campylobacter is one of the most common bacterial causes of diarrhoea worldwide and is closely tied to poultry. Floodwater through chicken coops can carry it, and it cross-contaminates easily from raw chicken in a disorganised post-flood kitchen.

Where it hides: boards and knives used for raw chicken, meat trays, sinks and untreated water.

Symptoms and risk: diarrhoea, sometimes bloody, cramps and fever; vulnerable people should see a doctor if not improving.

Prevention: separate raw-meat boards, cook chicken through and wash hands after handling raw meat.

Cleaning and spraying: not named on WHD's pages; part of the bacteria group the product covers. Remove grease first, then spray, and ask WHD for data.

No. 7: Vibrio, Including the Cholera Bacterium Health Agencies Monitor

Why here: Vibrio parahaemolyticus is a frequent cause of food poisoning from raw or undercooked seafood, especially in coastal and brackish areas. Vibrio cholerae, the cause of cholera, is something WHO and health agencies watch for when water and sanitation are badly disrupted. It ranks seventh because its link is mainly seafood and water rather than household surfaces.

Where it hides: seafood left unchilled after a power cut, containers for raw seafood and unsafe water.

Symptoms and risk: diarrhoea, cramps, nausea and vomiting. Large volumes of watery stool with weakness need hospital care immediately.

Prevention: eat only well-cooked seafood, discard unchilled seafood and drink safe water.

Cleaning and spraying: not named on WHD's pages; part of the bacteria group the product covers. Spraying helps kitchen surfaces after washing, but water and food safety depend on boiling and cooking.

No. 8: Toxin-Producing Bacteria After Power Cuts (Staphylococcus aureus and Bacillus cereus)

Why here: Staphylococcus aureus often comes from food handlers' hands or wounds; Bacillus cereus lives in soil and is linked with cooked rice left at room temperature. Both form toxins in food, and some of those toxins survive reheating. After floods, with no power and kitchens half-working, food is often cooked ahead and left out.

Where it hides: cooked rice and dishes left standing, powerless fridges, cooks' hands with cuts and leftover containers.

Symptoms and risk: sudden nausea, vomiting and cramps soon after eating, sometimes diarrhoea. Watch children and older adults for dehydration.

Prevention: cook and eat promptly, do not leave rice standing, cover hand wounds and wear gloves, and throw out anything doubtful.

Cleaning and spraying: neither is named on WHD's pages, and surface spraying cannot destroy toxins already in food. It helps by treating kitchen and fridge surfaces after washing before cooking resumes.

No. 9: Entamoeba histolytica, the Cause of Amoebic Dysentery

Why here: this single-celled parasite spreads through faecally contaminated water and food, and its cyst stage is environmentally tough. Risk rises when people drink untreated water or eat produce washed in dirty water.

Where it hides: unboiled water, raw vegetables, ice and unwashed hands.

Symptoms and risk: abdominal pain and loose stools, sometimes with mucus and blood, often developing more gradually. See a doctor for diagnosis.

Prevention: drink boiled or bottled water, avoid raw produce of doubtful origin and wash hands before eating.

Cleaning and spraying: it is a parasite, outside the virus, bacteria and fungi groups in the product information, so we make no claim. Safe water, cooked food and handwashing are the main defences; thorough washing physically removes contamination.

No. 10: Giardia and Cryptosporidium

Why here: both parasites spread through water contaminated with human or animal faeces, and CDC highlights them in unsafe drinking water. Cryptosporidium is well known for tolerating chlorine at normal treatment levels. They rank last because their link to household surfaces is weaker, but they are the reason to boil drinking water.

Where they hide: well water, storage tanks that floodwater entered, and water used for formula or ice.

Symptoms and risk: watery diarrhoea, bloating and cramps, sometimes lasting days; immunocompromised people and young children should see a doctor.

Prevention: boil water or use bottled water, clean storage tanks following local guidance, and wash hands well.

Cleaning and spraying: these are parasites outside the listed groups, so we make no claim. Spraying surfaces does not treat drinking water; boiling and proper water management do.

Kitchen and Restaurant Hotspots for Diarrhoea Germs After Floods

• Wooden boards and sponges: they soak sewage into the material and cannot be cleaned reliably. Replace them.
• Fridges and freezers that lost power: empty them, wash shelves and door seals, then disinfect.
• Ice bins and water dispensers: do not use until the system has been cleaned and checked.
• Sinks, taps and drains: sewage may back up, so wash and disinfect again.
• Staff and customer toilets: the starting point for germs moving from hands to food.
• Tables, chairs and serving trays: touched by many customers every day.

When these germs linger, the costs pile up: several customers or family members ill at once, a shop forced to close again just after reopening, lost stock, fast-spreading stories on social media, and regulars who hesitate to return even after the problem is fixed.

Why Dishwashing Liquid, Soap or Bleach Alone May Not Be Enough

Dishwashing liquid and soap remove grease and food residue, which is essential, but they are not designed to disinfect a whole room after sewage exposure. Bleach is often mixed too strong, leaving odours on dishes and corroding stainless steel, or too weak to work. Poured onto muddy floors, its active ingredient is used up by the dirt, and mixing it with acidic toilet cleaners or ammonia products can release irritating gases. Hand wiping also tends to cover only what is visible, missing lower walls, table legs, the undersides of shelves, the back of freezers and tile grout. Spraying by trained technicians after washing distributes disinfectant to these places more evenly.

WHD Post-Flood Disinfection Spraying with CHEMGENE HLD4H for Kitchens and Restaurants

According to service information, trained WHD technicians spray and/or ULV-fog (Ultra Low Volume fine mist) CHEMGENE HLD4H, a medical-grade UK disinfectant containing benzalkonium chloride and didecyldimethylammonium chloride. WHD's pages describe it as broad-spectrum against viruses, bacteria and fungi and list norovirus, Salmonella, SARS-CoV-2, human coronavirus 229E, RSV, H1N1, H5N1, HIV, hand, foot and mouth virus, vaccinia virus, mycobacteria and Bordetella pertussis, with 99.99% stated on the service page. Listed endorsements include the Department of Medical Sciences, Mahidol University, NHS England and EN 14476:2013+A2:2019. So the top-ranked norovirus and Salmonella are named directly.

For E. coli, Shigella, Campylobacter, Vibrio and rotavirus, we make no organism-specific claim; they belong to the bacteria or virus groups the product says it covers, and you can request test data from WHD. Parasites such as Entamoeba, Giardia and Cryptosporidium are managed through safe water, boiling and handwashing.

Spraying happens after mud removal and washing. People and pets leave the zone, food and dishes are stored away, and everyone returns at the time the technicians give, typically about 30 minutes according to service information. We do not claim there is no residue; food-contact surfaces should be rinsed with clean water afterwards as advised, and anyone with diarrhoea should see a doctor.

1. Survey: call 065-556-6294 or LINE @whd268 with the floor area, flood depth, type of business and planned reopening date.
2. Remove mud and wash: discard flooded food, ice, wooden boards and sponges; wash floors, walls and equipment; dry thoroughly.
3. Zone: kitchen, storage, toilets and dining area; store dishes; everyone leaves.
4. Spray: focusing on sinks, freezer seals, door handles, prep tables and toilets.
5. Re-enter: ventilate, rinse food-contact surfaces, then start cooking.

WHD also serves hospitals, schools, malls, airports, offices, airlines, banks and residential buildings, offers a free CHEMGENE spray bottle and WELLGIENIC wet tissues with the service, and can issue a tax invoice, handy for businesses.

10 Reasons to Spray Before You Cook Again

1. Norovirus and Salmonella are both named for the product used by the disinfection service.
2. It reduces the chance of sewage germs moving from surfaces to food.
3. Restaurants can reopen confidently and explain to customers what was done.
4. Disinfectant reaches lower walls, shelf undersides and behind freezers.
5. No risky chemical mixing in a poorly ventilated kitchen.
6. Technicians know kitchen workflow and store utensils correctly first.
7. It protects children, older adults and patients prone to dehydration.
8. Short wait, about 30 minutes per service information.
9. Tax invoices available; details on the service page.
10. Recovery is complete: discard, wash, dry, then disinfect.

Before and After

Example Case: Auntie Daeng Delays Reopening by Two Days

In this illustrative case, Auntie Daeng spent day one discarding freezer stock, two wooden boards, sponges, cloths and the flooded ice bin, washing pots and shelves, scrubbing the freezer seal and drying the shop with fans. On day two, WHD surveyed and zoned the kitchen, toilet and dining area; dishes went into closed cabinets and the family waited outside. After the re-entry time, technicians ventilated the shop and advised rinsing the prep table before cutting vegetables. On reopening day, a small sign explained the clean-up and new equipment, and regulars said they felt reassured.

Checklist

• Before: check electricity and gas; discard flooded food, seasonings, ice and anything from a long-unpowered fridge; replace wooden boards, sponges and cracked plastic; wash metal and glass; clean fridge seals; clean water tanks.
• After: re-enter on time and ventilate; rinse food-contact surfaces; use boiled or bottled water until authorities confirm tap water is safe; cook thoroughly and eat promptly; keep sick staff out of the kitchen; wash hands with soap.

FAQ

Can I keep canned food that was under water? CDC says undamaged, unswollen, non-leaking commercial cans can be kept after removing labels, washing and disinfecting the outside. Discard damaged cans and other packaged food that touched floodwater.

Will reheating make food safe? Not always. Some bacterial toxins survive reheating, so discard food left unchilled too long.

Can I use dishes right after spraying? Store them before spraying, then rinse food-contact items with clean water afterwards as technicians advise.

When should a restaurant book spraying? After washing and drying, leaving time for the wait and rinsing before cooking. WHD can help plan.

Does it kill E. coli or Shigella? They are not named on WHD's pages, so no tested claim; ask WHD for data.

What should I do about diarrhoea? Drink fluids and oral rehydration solution as health workers advise, and see a doctor for blood in stools, high fever, heavy vomiting, drowsiness or low urine.

Before You Cook Again, Let WHD Spray

Book Post-Flood Disinfection Spraying

Call 065-556-6294 | LINE @whd268

Related Services and References

• WHD Disinfection Spraying Service
• Residential Ozone Disinfection for lingering odours
• Daily News, DDPM flood update, 06:00 5 Oct 2026: dailynews.co.th/news/6249374
• WHO fact sheets: who.int; CDC Floods: cdc.gov/floods; Department of Disease Control: ddc.moph.go.th