After a flood, people ask "what germs are in my house?" and usually get answers one disease at a time: leptospirosis today, diarrhoea tomorrow, mold the day after. The reality is that a single flooded home typically hosts many kinds of germs at once: bacteria carried in by sewage and mud, viruses that sit on surfaces and travel on hands, and fungi that quietly colonise walls and furniture while they stay damp. Seeing all three groups as one picture helps you plan a recovery that does not leave any of them behind.

This article is a practical overview of what each group is, how it gets into a home, the symptoms it can cause, who is most at risk, and where the disinfection spraying service from World Health Disinfection (WHD) fits into the process. Our example is a home in the Chalong Krung Road area of Lat Krabang district, Bangkok, where water was still standing in early October 2026.

A Typical Scenario: A Three-Generation Townhouse Near Chalong Krung

(An illustrative example based on common situations, not a specific customer record.)

Nok lives in a two-storey townhouse in a soi off Chalong Krung Road. Three generations share the house: her mother, in her seventies and living with diabetes; Nok and her husband, who both work at factories in the nearby industrial area; and their three-year-old daughter, who has just started nursery. When heavy rain hit in late September, water crept up to the front gate and then into the ground floor, where it stayed for days. The family moved upstairs and only came down when they had to.

While the water sat in the house, Nok noticed several things at once. The downstairs bathroom smelled like the drains were backing up. Her husband, who waded out to work every day, developed itching between his toes. Their daughter had a day of diarrhoea after playing with a toy that had fallen into the water. Grey-green spots appeared on the living-room wall just above the waterline. And her mother coughed more whenever she spent time downstairs.

Nok was not facing five separate problems. She was looking at three groups of germs in one house: bacteria from sewage, viruses passed on through a toy, and fungi on skin and walls. It is a very common picture after a flood. Treating each person's symptoms is a doctor's job; making the home safe again needs a plan that deals with every group together.

The Situation on Chalong Krung Road, Lat Krabang, Early October 2026

According to a Thairath headline on 5 October 2026, the Bangkok Metropolitan Administration (BMA) updated its list of flooded main roads, and Chalong Krung Road still had water 15 to 25 cm deep. Earlier, on 26 September 2026, the BMA declared all 50 districts a disaster zone, and according to the Department of Disaster Prevention and Mitigation (DDPM) on 2 October 2026, 329,000 households in Bangkok were affected.

For people around Chalong Krung this means the water did not come and go in a day. It lingered. Standing water matters for germs: the longer it sits, the more contaminated sediment settles on surfaces, the deeper materials soak, and the more time mold has to establish itself. The area is also mixed, with housing estates, townhouses, dormitories and apartments for workers and students, small restaurants and businesses, so all three germ groups can turn up in many kinds of building.

The right move now, while the water is going down, is to have a plan ready rather than wait for smells or mold to appear first.

Group 1: Bacteria Carried by Sewage and Mud

Bacteria are single-celled organisms found everywhere, and most are harmless. Floodwater, however, gathers disease-causing bacteria from sewage, septic tanks, animal waste and soil and deposits them inside homes. The main ones to know:

Faecal bacteria: E. coli, Salmonella, Shigella

Escherichia coli mostly lives harmlessly in the gut, but some strains cause diarrhoea and cramps, occasionally with bloody stools. Salmonella causes food poisoning with fever, diarrhoea and abdominal pain. Shigella causes dysentery with mucus and blood in the stool. All three spread by the faecal-oral route: contaminated hands, food rinsed in unsafe water, and dishes that sat in floodwater.

Leptospira, the cause of leptospirosis

These bacteria come from the urine of rats and other animals and enter the body through cuts, scrapes, or the lining of the eyes, nose and mouth when people wade through water or handle contaminated mud. Warning signs include sudden high fever, headache, muscle pain (especially in the calves) and red eyes. Thailand's Department of Disease Control warns about leptospirosis with every flood. If these symptoms follow wading, see a doctor immediately and mention the floodwater exposure.

Indicator and opportunistic bacteria

Enterococcus is used as an indicator of faecal contamination in water. Staphylococcus and Streptococcus, which live on skin, can infect cuts picked up while wading or carrying furniture, causing swelling, redness and pus. Thai soil and water also harbour Burkholderia pseudomallei, the cause of melioidosis, and people with diabetes are at higher risk, which is another reason to wear boots and gloves whenever you handle mud.

Most at risk from bacteria: young children, older adults, people with diabetes or kidney disease, anyone with wounds or catheters, and anyone cleaning without protection.

Group 2: Viruses That Sit on Surfaces and Travel on Hands

Viruses are far smaller than bacteria and cannot multiply outside living cells, but many survive on surfaces long enough to reach the next pair of hands. After a flood, they fall into two broad types.

Gut viruses: norovirus, rotavirus, hepatitis A

Norovirus causes sudden vomiting and diarrhoea and is extremely contagious; a very small amount can make someone ill. Rotavirus is a major cause of severe diarrhoea in young children and can lead to dehydration quickly. Hepatitis A virus causes fever, fatigue, nausea and yellowing of the skin and eyes. All of them spread through water and food contaminated with faeces, and through surfaces that hands touch.

Crowding viruses: HFMD, RSV, influenza, COVID-19

During floods many people share small spaces: the upper floor of a house, a relative's home or an evacuation shelter. Hand-foot-and-mouth disease spreads easily among small children, with fever, mouth sores and a rash on hands and feet. RSV causes respiratory illness in infants and older adults, sometimes with breathing difficulty. Influenza and COVID-19 spread readily at close quarters. These viruses do not arrive in floodwater as such, but flood living conditions help them spread, and they can sit on toys, door handles, remote controls and tables.

Most at risk from viruses: small children who cannot yet wash their hands properly, older adults, pregnant women and people with chronic illness. If a child has a high fever, is unusually drowsy, refuses fluids, passes little urine or breathes rapidly, seek medical care at once.

Group 3: Fungi That Grow Quietly After the Water Recedes

Fungi differ from bacteria and viruses because they do not need to arrive with the floodwater: mold spores are already in ordinary air. What a flood supplies is moisture, the one thing mold needs to grow. WHO and the CDC advise drying a home as quickly as possible, generally within 24 to 48 hours, to reduce the chance of mold taking hold.

Household molds: Aspergillus, Penicillium, Cladosporium, Stachybotrys

Molds commonly found on walls, ceilings, wallpaper, mattresses and wooden furniture include Aspergillus, Penicillium and Cladosporium. On materials that stay wet for a long time, such as gypsum board or paper, Stachybotrys, often greenish-black, may appear. Breathing mold spores can cause a stuffy nose, cough and eye or throat irritation, and can trigger allergies and asthma. People with severely weakened immunity, such as those receiving chemotherapy, can be at risk of serious fungal lung infections.

Skin fungi: athlete's foot and Candida

Feet that soak in water or stay in wet shoes become soft and macerated, letting dermatophyte fungi cause athlete's foot, with itching and peeling between the toes. The yeast Candida can cause rashes in warm, damp skin folds. Wash feet with soap, dry them carefully, especially between the toes, and see a doctor if things do not improve or a wound becomes infected.

Most at risk from fungi: people with allergies, asthma or chronic lung disease, older adults, young children and anyone with weakened immunity.

Summary Table: Many Germs, One Flooded Home

The table shows why spraying is most useful when the whole house is treated as a space holding several germ groups, rather than chasing one organism.

What Happens When Many Germ Groups Share One Home

The whole family's health. With several groups present, each person may fall ill differently: a child with diarrhoea, an adult with itchy feet, a grandparent with a cough. The family ends up managing many problems at once, and people who were already unwell recover more slowly.

Rising costs. Doctor visits, medicines, transport and repeated repairs when mold comes back usually add up to more than a systematic restoration done right the first time.

Lost time. Factory and office workers in Lat Krabang may need leave to care for sick children or parents, just when work has piled up after the flood.

Rental and business impact. Dormitory and apartment owners need tenants to feel safe moving back in, and restaurants need customers to return. A single musty corner or patch of mold can push a tenant to leave.

Stress. Not knowing whether the house is safe keeps many families anxious, especially those with toddlers and elderly relatives.

Why Tackling One Germ Group at a Time Usually Fails

Treating only the smell. Musty odours usually come from mold and bacteria. Air fresheners and fans help briefly but leave the cause in place.

Cleaning only the kitchen. Kitchens get attention because of food, but door handles, stair rails and children's toys are just as much a route for viruses.

Scraping mold and painting over it. If the material is still damp, mold returns under the paint within weeks.

Using bleach on everything. Correctly diluted bleach is useful on some hard surfaces, but not on every material, and it must never be mixed with ammonia or other cleaners, as the CDC warns.

Assuming mosquito fogging covers it. More mosquitoes after a flood is a separate problem. Spraying surface disinfectant does not replace removing standing water to prevent dengue; empty and turn over containers as well.

A Restoration Plan That Covers All Three Germ Groups

WHO, the CDC and Thailand's Department of Disease Control share the same principle: clean first, then disinfect. This sequence is designed to cover bacteria, viruses and fungi together:

1. Wait until it is safe. Keep ground-floor power off until an electrician has checked it, and do not start while water is still high.
2. Protect yourself. Rubber gloves, boots, a mask and eye protection; cover all cuts to keep out bacteria such as Leptospira.
3. Throw out what cannot be saved. Mattresses, carpets, foam cushions, soft toys and other absorbent items that sat in water feed mold and bacteria.
4. Remove mud and wash. Use water and detergent on floors, lower walls and anything you keep.
5. Dry. Open doors and windows and run fans or dehumidifiers, within 24 to 48 hours where possible, to break the mold cycle.
6. Spray the whole home. Cover floors, walls, corners, high-touch points, and rooms the water did not reach but people walked through, to deal with bacteria and viruses on surfaces.
7. Follow up. Check for new mold weekly during the first month. If humidity stays high, fix the cause, such as leaks or materials that are still wet.

WHD Disinfection Spraying: Broad-Spectrum According to the Product Information

The WHD disinfection spraying service is carried out by trained technicians. According to the service information, they use both spraying and ULV (Ultra Low Volume) fogging, which disperses disinfectant as a fine mist that reaches corners and gaps.

The disinfectant is CHEMGENE HLD4H, a medical-grade product from the United Kingdom containing Benzalkonium Chloride and Didecyldimethylammonium Chloride. According to the product and service information, CHEMGENE is broad-spectrum, covering viruses, bacteria and fungi. The service page states 99.99% effectiveness, and the product page states 99.85% against COVID-19 within one minute. The service page lists endorsements and standards including the Department of Medical Sciences, Mahidol University, NHS England and EN 14476:2013+A2:2019, and clients such as hospitals, schools, shopping malls, airports, offices, airlines, banks and residential buildings.

Named Organisms Versus Germ Groups

According to the product and service information, the organisms named on WHD's pages are SARS-CoV-2 (COVID-19), Human Coronavirus 229E, RSV, influenza H1N1 and H5N1, HIV, norovirus, hand-foot-and-mouth disease virus, vaccinia virus, mycobacteria, Salmonella, Bordetella pertussis (whooping cough), plus bacteria in general and fungi. Other organisms in this article, such as E. coli, Leptospira, Shigella, rotavirus, hepatitis A, Aspergillus or Candida, are not named, so we make no organism-specific test claim for them. They belong to the bacteria, virus or fungi groups the product says it covers, and WHO and the CDC advise cleaning and then disinfecting flood-contaminated surfaces. If you need test data for a particular organism, ask WHD.

Importantly, we do not quote any number of strains, because neither the service page nor the product page gives one. The accurate wording is "broad-spectrum". For mold that has penetrated porous materials, spraying treats the surface, but you must also fix moisture and replace damaged materials. If a musty smell lingers, the residential ozone service can be considered as a complement.

Service Steps

1. Book. Share the size of the home, number of floors and how high the water rose.
2. Prepare. Remove mud, wash, dry, and put away food and personal items.
3. Technicians spray. Everyone in the household and all pets leave the zone being treated.
4. Wait about 30 minutes. According to the service information, then re-enter at the time the technician advises.

We do not claim the product leaves no residue. For food-contact surfaces and toys that children mouth, ask the technician about wiping or rinsing.

10 Reasons Chalong Krung Homes Should Plan Spraying That Covers Every Germ Group

1. The water stood for days. The longer it stands, the more time bacteria have to settle and mold has to take hold.
2. One home, several germ groups. Whole-home spraying avoids missing spots where viruses or bacteria linger.
3. A disinfectant stated to cover all three groups. CHEMGENE HLD4H is described as covering viruses, bacteria and fungi.
4. ULV reaches corners. Under stairs, behind cabinets, under beds and wall corners are often missed.
5. Protects small children. Toys and crawling areas are hotspots for gut viruses and HFMD.
6. Protects older and chronically ill relatives. People with diabetes or lung disease face risks from both bacteria and mold spores.
7. Trained technicians. They know how to cover a space systematically.
8. Short wait. About 30 minutes according to the service information, with re-entry when the technician says so.
9. Works for homes and businesses. Dormitories, apartments, restaurants and offices in Lat Krabang can request a tax invoice.
10. Extras for ongoing care. The promotion on the disinfection service page includes a CHEMGENE spray bottle and WELLGIENIC wet tissues.

Before and After: A Townhouse With Three Germ Groups

Example Case: A Four-Storey Dormitory Near Chalong Krung Road

(An illustrative example of a common situation.)

Ek owns a four-storey dormitory near Chalong Krung Road. Most tenants are factory workers and students. Water flooded the ground floor: the lobby, the coin laundry, the motorbike parking and four rooms. Upstairs tenants still had to walk through the ground floor every day, carrying mud and germs up the stairs and into the lift.

When the water receded, Ek split the work by germ group. First, bacteria from sewage: he washed the lobby, laundry and ground-floor rooms with water and detergent. Second, mold: he removed carpets and mattresses from flooded rooms and kept windows open with fans running for several days. Third, viruses spread by hands: he focused on lift buttons, stair rails, entrance doors and washing machines. Then he booked WHD to spray the ground floor, the stairwell and high-touch points on every floor, giving tenants notice to stay out of each zone during treatment.

Afterwards he left a spray bottle in the lobby, put up a sign encouraging handwashing, and reminded tenants to see a doctor if they developed fever after wading. Most tenants moved back in as normal and felt the owner genuinely cared about their health.

Three-Group Checklist: Before and After Spraying

For bacteria

• Wear boots and gloves when handling mud; cover every cut.
• Throw away food that touched floodwater; wash dishes with soap and clean water.
• Drink boiled or bottled water.

For viruses

• Wash hands with soap often, especially before eating and after using the toilet.
• Separate submerged toys; wash plastic ones and discard soft toys that cannot be cleaned.
• Sick children or older relatives should rest apart and see a doctor.

For fungi

• Dry the home as fast as possible with fans or dehumidifiers.
• Discard absorbent materials that stayed wet; never paint over damp walls.
• Wash and dry feet after wading.

On spraying day

• Everyone and all pets leave the treatment zone.
• Re-enter at the time the technician advises and ventilate.
• Wipe or rinse food-contact surfaces as the technician recommends.

FAQ: Many Germ Types After a Flood

Q: How many strains does the spraying service kill?
A: Neither the service page nor the product page states a number of strains. The wording used is "broad-spectrum", covering viruses, bacteria and fungi, with a list of certain named organisms. For organism-specific data, ask WHD.

Q: Do I need to know which germs are in my home before spraying?
A: No need to test for each one. WHO and CDC guidance is to assume flood-contaminated surfaces are contaminated, clean them and then disinfect. If someone at home is ill, tell the technician so the plan can be adjusted.

Q: Will mold stay away after spraying?
A: Spraying treats surfaces, but if materials stay damp or there is a leak, mold can return. Moisture must be fixed as well.

Q: Does disinfection spraying prevent dengue?
A: No. Dengue comes from Aedes mosquitoes. Remove standing water and prevent bites; that is separate from surface disinfection.

Q: Should upstairs rooms the water never reached be sprayed?
A: Consider high-touch points such as stair rails, handles and rooms the family shared during the flood, because germs travel on hands and shoes.

Q: How long must people stay out?
A: According to the service information, about 30 minutes, but always follow the technician's re-entry time.

Q: How do I contact WHD?
A: Call 065-556-6294 or message LINE @whd268.

One Home, Many Germs, One Complete Plan

Once the water is gone and the house is washed, let WHD finish with CHEMGENE HLD4H, a broad-spectrum disinfectant according to the product information.

Book Whole-Home Disinfection Spraying

Call 065-556-6294 · LINE @whd268

Related Links

• World Health Disinfection spraying service
• CHEMGENE HLD4H disinfectant
• Residential ozone disinfection

References

• Thairath, 5 October 2026: BMA update on flooded main roads
• World Health Organization fact sheets: https://www.who.int/news-room/fact-sheets
• CDC Floods: https://www.cdc.gov/floods/
• Thailand Department of Disease Control: https://ddc.moph.go.th/

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