The 2026 Floods and Why Respiratory Germs Matter

According to Thailand's Department of Disaster Prevention and Mitigation (DDPM), in an update at 06:00 on 5 October 2026 reported by Daily News, flooding had affected 26 provinces plus Bangkok, with 1,270,151 households affected.

After the water recedes, indoor humidity stays high. Plaster and timber hold moisture, ceiling boards remain wet, and soaked mattresses, sofas and carpets become ideal places for mold. At the same time, many people have spent days in shelters or crowded relatives' homes, where respiratory viruses pass easily from person to person.

Example Case: A Grandmother Whose Asthma Returned

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

Nok, in her early forties, lives in a two-storey townhouse with her mother, who is in her seventies and has long-standing asthma, and her six-month-old daughter. When water entered their street, the family moved to a relative's house where nearly ten people were sharing the space. A week later the water dropped and they rushed home. The ground floor had a waterline about half a metre high, the fabric sofa was swollen, the curtains were covered in tiny black dots, and the storeroom under the stairs smelled so musty that the door had to stay open.

Nok and her husband spent two days hauling out damaged items, washing floors with ordinary cleaner and pointing fans at the walls. On the third night, her mother began coughing, wheezing and using her inhaler more often. The baby developed a runny nose and cough. A doctor explained that the symptoms could come both from respiratory viruses picked up while living in a crowded house and from mold spores in the damp home triggering asthma. The doctor treated them and advised tackling damp and mold seriously before the patients moved back permanently. Which germs deserve attention first? The ranking below answers that.

How We Ranked Respiratory Germs After Floods

This is an editorial ranking by the World Health Disinfection (WHD) team, intended to help readers prioritise. It is not an official ranking by any government agency, and it is not based on any single set of case statistics. We weighed five criteria:

1. Link to flooding: how often the germ or germ group appears in post-flood guidance from the WHO, the US CDC or Thailand's Department of Disease Control.
2. Severity: whether it usually causes mild symptoms or can lead to pneumonia and hospital care.
3. Who is at risk: how strongly it affects infants, older adults, pregnant women, people with chronic illness or weak immunity.
4. Persistence in damp conditions: whether it survives or multiplies in a wet home after the flood (described qualitatively, without exact hours or days).
5. Ease of spread: through droplets, contaminated surfaces, or inhaled mist and dust, especially in crowded places such as shelters.

A lower rank does not mean harmless. It may simply mean the germ is less likely to be found in an ordinary home after a flood, or that the at-risk group is narrower. If anyone has a high fever, rapid breathing, chest pain or quickly worsening symptoms, see a doctor immediately rather than guessing which germ is responsible.

No. 1: Aspergillus Mold, Spores Released From Wet Walls and Furniture

Why it ranks first: Mold is something the WHO and CDC warn about after nearly every flood, because it can grow in almost any building that does not dry quickly. Aspergillus is one of the molds commonly found in damp buildings, and its spores are small enough to float in the air and be inhaled unnoticed. It scores high on flood link, persistence and the number of people affected.

Where it hides: gypsum walls and ceiling boards that soaked up water, the back of wardrobes pushed against walls, under carpets and underlay, waterlogged mattresses and sofas, cardboard boxes, books and piles of fabric left closed up, and dust in low-mounted air-conditioner filters.

Symptoms and at-risk groups: most people may experience a blocked nose, sneezing, itchy eyes, coughing or throat irritation. People with allergies or asthma may have flare-ups. Those with severely weakened immunity, such as people receiving chemotherapy, organ transplant recipients or people on immune-suppressing medicines, face a higher risk of serious lung infection and should avoid cleaning moldy homes themselves.

Prevention: dry the house as fast as possible, open doors and windows, discard porous materials that were soaked and cannot be cleaned, and wear an N95 mask, gloves and goggles when handling moldy items. Avoid dry sweeping, which throws spores into the air.

How cleaning and spraying help: removing moldy materials and scrubbing hard surfaces is the main step. Spraying disinfectant onto cleaned surfaces afterwards reduces what remains on walls, floors and hard furniture. According to WHD's product information, CHEMGENE HLD4H is stated to cover fungi as a group. We do not claim a specific test result against Aspergillus; you can ask the team for test data on this organism.

No. 2: Respiratory Syncytial Virus (RSV), a Threat to Babies and Older Adults

Why it ranks second: Thai floods usually arrive in the rainy season, when RSV is already circulating. Evacuation brings small children from different families into close contact, so the virus spreads easily. RSV can cause bronchiolitis or pneumonia in infants and older adults, so it scores high on severity and at-risk groups.

Where it hides: RSV spreads through droplets from coughs and sneezes, and through touching contaminated surfaces and then the nose or eyes. Hotspots include toys, cot rails, feeding bottles, bibs, door handles, dining tables and shared seating.

Symptoms and at-risk groups: it starts like a cold with a runny nose, cough and fever. Young children may breathe fast, wheeze or feed poorly. Watch for laboured breathing, ribs pulling in, or pale lips, and seek care quickly. Premature babies, children with heart or lung conditions, and older adults with chronic illness need extra care.

Prevention: wash hands often, keep babies away from anyone with a cough or cold, do not share bottles or cups, clean toys and frequently touched surfaces, and keep rooms ventilated.

How cleaning and spraying help: according to WHD's service and product information, CHEMGENE HLD4H is stated to cover RSV. Spraying surfaces in nurseries, living rooms and crawling areas after cleaning reduces the chance of virus lingering where little hands touch. Spraying cannot stop droplet spread between people, so it must go together with handwashing and keeping sick people apart.

No. 3: Influenza, Fast-Spreading Where People Crowd Together

Why it ranks third: the Department of Disease Control already warns about influenza in the rainy season. During evacuation, families share sleeping spaces, bathrooms and utensils, raising the risk. Influenza can be serious for older adults, young children, pregnant women and people with chronic disease.

Where it hides: droplets in poorly ventilated rooms and frequently touched surfaces such as door knobs, light switches, remote controls, stair rails, phones and dining tables. After a flood many households keep windows shut against mosquitoes or rain, reducing airflow.

Symptoms and at-risk groups: sudden high fever, muscle aches, headache, fatigue, dry cough and sore throat. Some people develop pneumonia. People with diabetes, heart, lung or kidney disease should see a doctor early.

Prevention: get vaccinated as advised by doctors and health authorities, wear a mask when sick, wash hands, keep personal items separate and rest at home when ill.

How cleaning and spraying help: WHD's service information states the disinfectant covers influenza H1N1 and H5N1. Spraying shared surfaces after cleaning is especially sensible when someone has just recovered, or when the home hosted several families during the flood.

No. 4: SARS-CoV-2 (COVID-19), Still Circulating

Why it ranks fourth: COVID-19 is no longer at pandemic levels, but the virus still circulates. Floods bring crowding, poor sleep and stress, and older adults and people with chronic illness can still become seriously ill.

Prevention: masks in crowded spaces, handwashing, distance where possible, vaccination as advised and good ventilation.

How cleaning and spraying help: WHD's product information lists results against SARS-CoV-2 and Human Coronavirus 229E; the service page states 99.99% efficacy and the product page states 99.85% against COVID-19 within one minute. Surface spraying after cleaning is a reasonable choice for homes with a recent patient or offices reopening.

No. 5: Legionella, Bacteria in Stagnant Water Systems

Why it ranks fifth: Legionella grows in warm, stagnant water inside building plumbing, water heaters, showerheads, cooling towers and storage tanks left unused. After floods, many buildings stay closed for days and water sits still in pipes, which is why the CDC offers guidance on managing water systems in buildings that have been shut. It causes Legionnaires' disease, a form of pneumonia that can be severe in older people, smokers and those with chronic illness. It is less likely in ordinary homes than in large buildings, so it sits mid-table.

Where it hides: showerheads, rarely used taps, storage water heaters, rooftop tanks, and cooling towers in condos, hotels and offices.

Symptoms and at-risk groups: infection comes from inhaling contaminated water mist, not normal drinking. Symptoms include high fever, cough, shortness of breath and muscle pain. People over fifty, smokers and those with chronic lung disease or weak immunity are more at risk.

Prevention: flush taps and showers before use, clean showerheads and water heaters per manufacturer guidance, and have large buildings checked under a proper water management plan.

How cleaning and spraying help: to be clear, surface spraying is not the way to manage Legionella inside plumbing; that requires water-system treatment. Spraying helps reduce germs on bathroom surfaces, tiles and damp areas after scrubbing. Legionella belongs to the bacteria group the product says it covers, but we do not claim a specific test result; ask the team for test data.

No. 6: Burkholderia pseudomallei (Melioidosis) From Soil and Mud

Why it ranks sixth: the Department of Disease Control regularly warns about melioidosis in the rainy season, especially in the Northeast. The bacterium lives in soil and water. Wading, shovelling mud or outdoor work raises exposure, and it can enter through wounds, inhaled mist or dust, or swallowing. Pneumonia is a common presentation, but because it is concentrated in certain regions, it ranks mid-table.

Where it hides: mud left in homes, under raised houses, yards, gardens, animal pens, and unwashed boots and shovels.

Symptoms and at-risk groups: fever, cough, chest pain, abscesses or infected wounds. People with diabetes, kidney disease, heavy alcohol use or weak immunity are key risk groups. If you develop fever after wading or mud work, tell your doctor about the exposure.

Prevention: wear boots, rubber gloves and a mask, cover wounds, avoid unnecessary wading, and wash immediately after work.

How cleaning and spraying help: removing mud and washing floors is the key step. Spraying cleaned surfaces then reduces remaining bacteria. It belongs to the bacteria group the product says it covers; we do not claim a specific test result and you may request test data.

No. 7: Streptococcus pneumoniae, a Common Cause of Pneumonia

Why it ranks seventh: pneumococcus is a leading cause of community bacterial pneumonia and often strikes after influenza or other viruses weaken the body. Exhaustion, poor sleep and crowding after floods raise the odds, but it is not carried by floodwater itself.

Where it hides: in the nose and throat of some healthy people, spreading via droplets, shared utensils and hands.

Symptoms and prevention: fever, productive cough, fast breathing and chest pain. Young children, older adults, smokers and people with chronic disease are more at risk. Pneumococcal vaccination for risk groups, as advised by a doctor, is the main protection.

How cleaning and spraying help: it belongs to the bacteria group the product says it covers. Spraying reduces contamination on dining tables and areas a patient used, but it does not replace vaccination or treatment. No specific test result is claimed.

No. 8: Adenovirus, Fever, Sore Throat and Pink Eye

Why it ranks eighth: adenovirus causes fever, sore throat, bronchitis and conjunctivitis, and some types cause diarrhoea. It is fairly hardy on surfaces and spreads among children in shared spaces. Most cases are mild.

Where it hides: shared towels, pillows, toys, door handles and unclean water.

Prevention: separate towels, wash hands, avoid rubbing eyes, and clean shared toys and surfaces.

How cleaning and spraying help: adenovirus belongs to the virus group the product says it covers; we do not claim a specific test result. Spraying after cleaning reduces it on shared surfaces, and test data can be requested.

No. 9: Other Household Molds: Stachybotrys, Penicillium and Cladosporium

Why it ranks ninth: besides Aspergillus, common post-flood molds include Stachybotrys (black mold on cellulose materials that stay wet, such as gypsum paper and wood), Penicillium (blue-green patches on fabric, books and food) and Cladosporium (dark patches on window frames, curtains and grout). These usually cause irritation and allergy rather than serious infection, so they rank ninth, although they are found in a very large number of homes.

Prevention: discard deeply moldy porous items, reduce humidity with ventilation or dehumidifiers, fix leaks, and never paint over mold without cleaning first.

How cleaning and spraying help: after removal and scrubbing, spraying reduces what remains on hard surfaces. The product is stated to cover fungi as a group; no specific test result is claimed for each species. If musty air persists, WHD's residential ozone disinfection can be a complementary service.

No. 10: Bordetella pertussis (Whooping Cough), a Risk for Babies in Shared Shelters

Why it ranks tenth: whooping cough is not carried by floodwater, but it spreads very easily in crowded places and is dangerous for babies who are not fully vaccinated. Families with infants in shelters or relatives' homes should know about it.

Symptoms and prevention: it begins like a cold, then progresses to bouts of coughing, sometimes with a "whoop". Babies may not cough but may pause breathing or turn blue, which needs hospital care at once. Vaccination on schedule, and advice for pregnant women from their doctor, are the best protection.

How cleaning and spraying help: WHD's product information states that the disinfectant covers Bordetella pertussis. Spraying surfaces in a baby's room after cleaning reduces surface contamination, but vaccination remains the strongest defence.

Why Soap, Floor Cleaner or Bleach Alone May Fall Short

Washing with water and detergent is essential: it removes mud, grease and dirt where germs shelter. But cleaning removes dirt; it does not directly disinfect, so some germs remain. Bleach mixed at the wrong strength may underperform or irritate the airways, which people with asthma should avoid. Never mix bleach with ammonia or certain toilet cleaners, as dangerous gases can form. Wiping a whole house with one cloth moves germs around, and a quick wipe may not leave the product in contact long enough. Fans blown onto moldy walls and air fresheners masking odours do not remove the cause, and painting over mold usually lets it return. That is why the WHO and CDC recommend cleaning first, then disinfecting flood-contaminated surfaces.

WHD's Post-Flood Disinfection Spraying Service

WHD's disinfection spraying service uses trained technicians who spray and/or ULV-fog (Ultra Low Volume fine mist) with CHEMGENE HLD4H, a medical-grade disinfectant from the UK containing Benzalkonium Chloride and Didecyldimethylammonium Chloride. According to the service information it is a broad-spectrum disinfectant covering viruses, bacteria and fungi, listing COVID-19, RSV, H1N1, H5N1 and hand-foot-mouth virus, with a stated 99.99% efficacy. The page lists the Department of Medical Sciences, Mahidol University, NHS England and EN 14476:2013+A2:2019, and customers including hospitals, schools, malls, airports, offices, airlines, banks and residential buildings.

1. Survey: assess damage, waterlines, mold and rooms used by vulnerable people.
2. Mud removal and washing: remove mud, discard damaged porous items and wash surfaces first.
3. Zoning: plan room order, protect or move electronics, food and personal items; people, pets and plants leave the zone.
4. Spraying: technicians cover floors, lower walls, handles, switches, counters and hard furniture.
5. Re-entry: wait for the time the technicians advise (about 30 minutes per the service information), ventilate, then use the space.

Spraying does not replace mud removal, drying or leak repairs, and we do not claim it leaves no residue. Anyone who is ill should see a doctor. Promotion per the service information: a free CHEMGENE spray bottle and WELLGIENIC wet tissues, with tax invoices available.

10 Reasons to Book Disinfection Spraying When Respiratory Germs Worry You

1. Reduces germs on surfaces everyone touches, the route from hands to face.
2. The disinfectant's listed organisms include RSV, influenza and COVID-19. See service details
3. Fine-mist equipment reaches corners, under furniture and lower walls.
4. Treats walls and floors after mold removal, before allergy sufferers return.
5. Your family avoids handling concentrated chemicals or mixing products.
6. Clear zoning and re-entry times limit unnecessary exposure.
7. Suits homes with babies, older adults or people with lung conditions. Talk to the team
8. Works for homes, condos, offices, shops, clinics and schools reopening.
9. Saves time for exhausted families trying to get back to normal.
10. You can ask for test data on specific germs and request tax invoices.

Before and After

Results vary with damage, remaining moisture and ongoing care. In the example case, Nok discarded the sofa and curtains, had swollen gypsum removed, washed everything, then booked spraying room by room while the family waited outside. Her mother returned after her doctor's treatment, and Nok kept ventilating and running a dehumidifier.

Recovery Checklist

• Have electrics checked before re-entry; never run generators indoors (carbon monoxide).
• Wear an N95 mask, gloves, goggles and boots for mud and mold work.
• Keep asthmatics, immunocompromised people, pregnant women and small children away during heavy cleaning.
• Ventilate; do not blow fans directly at mold.
• Discard soaked mattresses, carpets and fabric sofas that cannot dry.
• Clean or replace air-conditioner filters; have flooded units checked.
• Flush taps and showers and clean showerheads.
• Wash hard surfaces before spraying; leave the zone during spraying and follow re-entry times.
• Afterwards, keep humidity down and watch for symptoms; see a doctor for fever or breathing difficulty.

FAQ: Respiratory Germs After Floods

Why is everyone coughing after we moved back?

It can be viruses caught while living in crowded conditions, mold spores and dust in a damp house, or both. See a doctor and deal with damp and mold at the same time.

Is this an official ranking?

No. It is WHD's editorial ranking based on flood link in WHO, CDC and Department of Disease Control guidance, severity, risk groups, persistence and ease of spread.

Will spraying stop colds spreading at home?

It reduces germs on surfaces but not droplet spread. Keep washing hands, masking when sick and following vaccination advice.

Can we just spray over black mold?

No. Remove deeply moldy porous materials, scrub and dry hard surfaces, then spray. Large areas need professional assessment.

Does the product cover Legionella or melioidosis?

Both belong to the bacteria group the product says it covers, but no specific test result is claimed. Ask us for test data. Legionella in pipes needs water-system treatment.

How long before we can go back in?

About 30 minutes per the service information, but always follow the technicians' advice and ventilate first.

Help Your Home Breathe Easy Again

Finished the cleanup but still worried about mold, viruses and bacteria? Talk to World Health Disinfection about a spraying plan for your home.

Book Post-Flood Disinfection Spraying

Call 065-556-6294 | LINE @whd268

Related Services and References

• WHD Disinfection Spraying Service
• Residential and Building Ozone Disinfection
• Daily News, DDPM flood update at 06:00, 5 October 2026: https://www.dailynews.co.th/news/6249374/
• WHO 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/