Example Case: Rice Sacks in the Granary Turning Fluffy and Speckled

This is a typical scenario built from situations common after mountain flash floods; it is not the story of a real person. Mae Oun lives in a wooden house by a stream with her husband and seven-year-old grandson. One night heavy rain does not stop, the stream rises fast and floods the house in the dark. The family carries the boy to higher ground, but the paddy and milled rice in the granary next to the house, the mattresses, pillows and blankets all go under.

Three days later, with the water gone and the sun out, Mae Oun opens the granary. The bottom sacks smell sour and musty, and the rice is covered in fluffy white-grey mould with small black dots. The mattresses drying outside are mouldy inside too. She hates to waste a year's harvest and thinks of sun-drying the better-looking rice to cook. Her husband, who has had diabetes for years, starts carrying the sacks out bare-handed and without a mask.

Their daughter, who works in town, phones and looks things up. She tells them flooded, mouldy rice should not be eaten, soaked mattresses should go, her diabetic father should not handle mouldy material, and anyone with a wound, unusual cough or facial swelling should see a doctor quickly. After a flash flood, reluctance to waste things and sheer exhaustion often push people into risks without realising it.

The Mae La Noi, Mae Hong Son Flash Flood of 2026: What the News Reported

According to Daily News (report of 18 September 2026), on the night of 17 September 2026 (B.E. 2569) heavy rain in Mae La Noi District, Mae Hong Son sent flash floods down the Mae Hu stream, the La River and the I Nai stream, flooding 3 villages: Moo 1 Ban Mae La Noi, Moo 2 Ban Pa Mak and Moo 9 Ban Thung Saraphi, covering 7 communities. More than 50 riverside households were affected and 5 pieces of infrastructure were damaged, with losses of no less than 30 million baht.

A night-time flash flood leaves little time to move belongings. Mattresses, pillows, blankets, clothes, rice sacks, dry food, wooden furniture and wall linings, all absorbent, usually end up underwater. Add the damp mountain air of the rainy season and silt full of rotting plant matter, and a house after the flood becomes ideal for mould.

Nationally, Department of Disaster Prevention and Mitigation data as of 06:00 on 7 October 2026 (B.E. 2569) showed flooding in 27 provinces plus Bangkok, covering 123 districts, 984 subdistricts, 1,154,875 households and more than 3.1 million people. Post-flood mould in 2026 is a problem many areas face at the same time.

What Are Mucor and Rhizopus? Are They "Black Fungus" or "Slime Mould"?

Mucor and Rhizopus are moulds in the group scientists call the order Mucorales. They are everywhere in nature: soil, rotting plants, compost, straw, decaying fruit and stale bread. They grow very fast, with fluffy white or grey threads and tiny black dots, which are spore sacs; some Rhizopus species are known as "bread mould". Their spores are tiny and easily become airborne when mouldy material is moved or swept.

"Black fungus" is a media name for the infection these moulds can cause, known medically as mucormycosis. It is uncommon but serious, because the fungus can damage tissue until it turns dark. "Slime mould", a term some people search, refers scientifically to a different group of organisms, not Mucor or Rhizopus. This article uses Mucor and Rhizopus to avoid confusion.

Is black fungus dangerous? For most healthy people, breathing in normal amounts of these spores does not cause infection. But heavy mould growth indoors can trigger allergies, sneezing, a blocked nose, itchy eyes and asthma attacks. Severe mucormycosis usually affects people with weak immunity or certain conditions, and they need extra protection after a flood.

How Do Mucor and Rhizopus Spread, and Why Do Floods Make Mould Grow So Fast?

These moulds do not pass from person to person. People are exposed from the environment in three main ways. Breathing spores released from mouldy material, for example when pulling out mattresses, carrying rice sacks or dry-sweeping. Through wounds, when grazes, cuts or puncture wounds touch soil or mud containing the fungus, something medical reports have described after some natural disasters overseas. And eating mouldy food, which may also contain toxins from other moulds growing alongside.

Floods speed up mould because three things arrive together: high humidity, warmth and food for the mould, meaning organic matter in mud, wood, fabric, paper, starch and grain. WHO and CDC both note that if wet materials are not dried within 24 to 48 hours, mould begins to grow. In mountain areas like Mae La Noi, where the rainy season is humid and sunshine scarce, drying a house is harder than on the plains.

Mucor and Rhizopus grow especially fast on starchy and sugary foods such as rice, sticky rice, bread, fruit and animal feed, so flooded granaries and food stores are among the first places they appear, while wooden walls, ceilings and furniture usually host a mix of moulds.

Symptoms of Mould Exposure After a Flood, and Warning Signs That Need a Doctor

Common symptoms in a heavily mouldy home are sneezing, a blocked or runny nose, a cough that will not stop after the water recedes, sore throat, itchy or red eyes, itchy skin rashes and worse asthma in people who already have it. These usually ease away from the mouldy space and are a sign that mould is still present in the home.

For mucormycosis, which is uncommon but needs urgent treatment, warning signs include fever, headache, pain or swelling on one side of the face, sinus pain, one-sided nasal blockage, bloody or dark nasal discharge, black patches on the nose or roof of the mouth, swollen eyes, double vision, coughing blood, chest pain, breathlessness, or a skin wound with dark edges that is painful, red and spreading fast. If someone in a higher-risk group has these signs, go to hospital at once and tell the doctor about the flood and any cleaning of mouldy items.

This is to show when to seek care, not for self-diagnosis. Do not buy antifungal or steroid medicines on your own, as some can lower immunity. Fungal infections must be treated under a doctor's care.

Who Is Most at Risk After the Mae La Noi Flood 2026?

Those most at risk of severe Mucor and Rhizopus infection are people with poorly controlled diabetes, especially anyone who has had diabetic ketoacidosis; cancer patients on chemotherapy; people with low white blood cell counts; organ or bone marrow transplant recipients; people on high-dose steroids or long-term immunosuppressants; people with iron overload; and people with large wounds or burns.

For mould allergies and breathing problems, add people with asthma or chronic lung disease, young children, older adults and pregnant women. The safe approach is for these groups to stay out of the house while mouldy items are removed and cleaning is done, and return only when the home is dry, clean and disinfected.

Where Mould Hides at Home After a Flash Flood

Check first the granary and food store, especially sacks on the floor; bedrooms with wet mattresses, pillows and blankets; wooden and plywood walls that soaked water into the grain; gypsum ceilings and wall panels; closed wardrobes and shoe cabinets with poor airflow; the area under the house where mud dries slowly; and fridges where food rotted during power cuts.

Mould does not grow only where you can see it. It often starts behind cabinets, under wooden floors or inside wall cavities before stains appear. Signs of hidden mould include a damp, musty smell that stays after washing, spots or rings on walls, peeling paint, swollen wood, and sneezing or a blocked nose every time you are in a particular room.

What Happens When Mould Is Left to Grow

Health: family members suffer allergies, chronic cough and asthma attacks, while people with diabetes or weak immunity live in a riskier environment. Property: long-standing mould eats into wood, fabric and paper, so more must be replaced and repairs cost more. Food: mouldy rice and dry goods must be thrown out, and eating them to avoid waste is a health risk. Peace of mind: a musty smell that never fades makes a family feel the house is never quite home again.

Why Wiping Mould Away or Painting Over It Is Not Enough

Many homes wipe off visible mould and then paint over it or spray air freshener. It looks clean for a while, but if wood or walls are still damp the mould soon returns. Dry-sweeping or dusting mould is also common, and it blows spores through the house and straight into the cleaner's lungs.

Porous, absorbent materials such as mattresses, pillows, carpets, gypsum ceilings and paper generally cannot be made safe once flooded and mouldy; CDC advises throwing them away. Hard surfaces such as tiles, metal, plastic and smooth wood can be washed with water and detergent, dried, and then disinfected. Pouring strong bleach onto mould without cleaning first, or mixing products, does not work well and risks toxic fumes.

Above all, moisture is the root cause. No spray or chemical works for long while dampness remains. Remove damaged materials, ventilate, use fans or dehumidifiers and fix leaks first; then disinfection can genuinely finish the job.

WHO, CDC and Thai DDC Guidance: Dry, Remove, Protect Yourself, Then Disinfect

The World Health Organization's guidance on dampness and mould in buildings stresses that the most important step is controlling moisture and removing what the mould is growing on. For flooded homes, the US CDC advises drying the house within 24 to 48 hours where possible, discarding absorbent mouldy materials, washing hard surfaces with water and detergent, and wearing protective gear while cleaning mould: an N95 mask, rubber gloves, goggles without vents and boots.

CDC also advises that people with weak immunity, asthma or lung disease avoid cleaning mould themselves. Thailand's Department of Disease Control warns about flood-related respiratory and skin illness and advises discarding food that is mouldy or touched floodwater. WHD's spraying service follows the same principle: it comes after removal, washing and drying, never instead of them or of medical care.

WHD Disinfection Spraying With CHEMGENE HLD4H After the Mae La Noi Flood 2026

World Health Disinfection (WHD) provides disinfection spraying for homes, buildings and businesses. According to the service information, trained technicians spray and/or ULV-fog (Ultra Low Volume fine mist) with CHEMGENE HLD4H, a medical-grade disinfectant from the United Kingdom containing Benzalkonium Chloride and Didecyldimethylammonium Chloride.

According to the service information, the product is stated to cover viruses, bacteria and fungi, including COVID-19, RSV, H1N1, H5N1 and hand-foot-mouth virus, with a stated 99.99% efficacy. The service page lists approvals or references from Thailand's Department of Medical Sciences, Mahidol University, NHS England and EN 14476:2013+A2:2019.

To be straightforward: Mucor and Rhizopus are fungi, in the fungi group the product says it covers, but these two genera are not named individually on WHD's pages. For test data on them, ask WHD directly. Spraying does not replace throwing away mouldy materials and does not solve ongoing dampness. For musty smells in closed rooms, residential ozone disinfection can be considered as a complementary service.

The Process When a Home Has a Mould Problem

1. Contact and survey. Send photos of mouldy areas, floor area, the flood line and building materials by phone or LINE. WHD is based in Bang Khae, Bangkok 10160, with no branch in Mae Hong Son; for upcountry jobs, contact the team first to arrange a date.
2. Removal, mud-out and washing. Discard mouldy mattresses, carpets, ceilings and absorbent materials, remove mud and wash hard surfaces while wearing an N95 mask, gloves and goggles.
3. Drying and zoning. Ventilate until the house is dry. Technicians zone the space, food and personal items are put away, and people and pets leave the zone.
4. Spraying. Technicians spray or ULV-fog CHEMGENE HLD4H, focusing on lower walls, wooden floors, cabinets, the granary and former mould spots.
5. Waiting and re-entry. According to the service information, wait about 30 minutes, then use the space normally, following the time technicians give on site and keeping the home dry.

According to the service information, customers receive a free CHEMGENE spray bottle and WELLGIENIC wet wipes, and a tax invoice is available. Prices and dates depend on location and job size, so please ask directly.

10 Reasons to Disinfect After a Flood When Mould Takes Hold

1. Mountain homes stay damp for long, and mould grows quickly after flash floods.
2. Mucor and Rhizopus are fungi, and the WHD disinfection spraying service uses a product stated to cover fungi, bacteria and viruses.
3. ULV mist reaches wall gaps, under cabinets and hard-to-wipe surfaces.
4. It treats surfaces after mouldy items are removed, helping limit regrowth while the house stays dry.
5. Trained technicians work zone by zone without missing key spots.
6. No mixing chemicals yourself and risking harmful fumes.
7. It helps protect people with diabetes or asthma, children and older adults.
8. It uses a medical-grade product used in hospitals and airports according to the service information.
9. Shops, homestays and restaurants can reopen with confidence, and a tax invoice for the spraying service is available.
10. You keep a spray bottle and wet wipes for ongoing care.

Before and After: A Wooden Streamside House With Mould

Example Case: A Riverside Homestay After the Flash Flood

This is an illustrative scenario. Ton runs a five-room wooden homestay by the river. The flash flood put three ground-floor rooms under about half a metre of water. A week later the closed rooms smelled musty, the mattresses had mould spots and the lower walls showed white-grey growth. He worried about guest complaints and did not want his asthmatic staff member doing the cleaning.

Ton contacted WHD on LINE with photos of each room. The team advised discarding mouldy mattresses and curtains, having staff without lung conditions wash hard surfaces in N95 masks, and running fans for several days first. Once the rooms were dry, technicians sprayed room by room with everyone out of each zone. After the wait the technicians gave, Ton aired the rooms, refurnished, and considered ozone treatment for rooms that still smelled musty.

Checklist: Preventing Mucor and Rhizopus Mould After a Flood

• Open doors and windows and use fans or dehumidifiers to dry the house fast.
• Throw out rice, dry goods and any food that was flooded or mouldy; do not sun-dry and eat it.
• Discard soaked, mouldy mattresses, pillows, carpets and gypsum ceilings.
• Wear an N95 mask, rubber gloves, goggles and boots when removing mouldy items.
• Never dry-sweep mould; dampen it first and bag it securely.
• People with diabetes, weak immunity or asthma should not clean mould.
• Cover wounds before handling mud and wash any cut with soap and clean water at once.
• Facial swelling, one-sided sinus pain, bloody nasal discharge or a dark-edged wound: go to hospital now.
• Remove, wash and dry first, then book disinfection spraying.

FAQ: Black Fungus, Mucor, Rhizopus and Mould After a Flood

What is black fungus?

A media name for mucormycosis, an infection caused by moulds such as Mucor and Rhizopus. It is uncommon but serious, mostly in people with weak immunity or poorly controlled diabetes.

Is black fungus dangerous?

For most healthy people it does not cause infection, though indoor mould triggers allergies and asthma. People in higher-risk groups can become seriously ill and need a doctor at the first warning signs.

How does black fungus spread?

Not person to person. Exposure comes from breathing spores, from wounds touching soil or mud, and from mouldy food.

Is slime mould the same as black fungus?

No. Slime moulds are a different group of organisms; black fungus relates to Mucor and Rhizopus.

Can I eat rice that went mouldy after a flood?

No. Throw away flooded or mouldy rice; sun-drying or rinsing does not make it safe.

What should I do about mould on walls after a flood?

Dry the house, discard absorbent mouldy materials, wash hard surfaces with water and detergent while wearing an N95 mask, then disinfect.

Is a cough that will not stop after the flood linked to mould?

It may be mould allergy, but there are other causes. See a doctor for a long cough, fever, chest pain or coughing blood.

Does disinfection spraying deal with mould?

The product is stated to cover fungi as a group; Mucor and Rhizopus are not named individually, so ask WHD for test data. Always remove mouldy items and dry the house before spraying.

How do I find a disinfection service near me in Mae Hong Son?

WHD is in Bang Khae, Bangkok, with no branch in Mae Hong Son. Call 065-556-6294 or LINE @whd268 to ask about upcountry service and book.

The Flash Flood Has Passed in Mae La Noi 2026. Let WHD Help Finish the Mould Clean-Up

Mouldy items are out and the house is dry, but you are worried the mould will come back? Talk to the WHD team.

See the Disinfection Spraying Service

Call 065-556-6294 | LINE @whd268

Related Services

• WHD Disinfection Spraying Service
• CHEMGENE HLD4H Disinfectant
• Residential Ozone Disinfection for musty post-flood air

References

• Daily News, Mae La Noi, Mae Hong Son flash flood (18 September 2026): https://www.dailynews.co.th/news/6201060/
• Government Public Relations Department, DDPM data as of 7 October 2026: https://www.prd.go.th/th/content/category/detail/id/33/iid/548715
• World Health Organization, Fact sheets: https://www.who.int/news-room/fact-sheets
• CDC, Floods: https://www.cdc.gov/floods/
• Department of Disease Control, Thailand: https://ddc.moph.go.th/