The 2026 Floods Pushed Rats and Cockroaches Indoors

According to Thailand's Department of Disaster Prevention and Mitigation, in a 06:00 update on 5 October 2026 reported by Daily News, flooding affected 26 provinces plus Bangkok and 1,270,151 households. During high water, rats swim and climb to upper floors, ceilings, cupboards and shelves, while cockroaches from drains and sewage pits crawl up through waste pipes and wall cracks. After the water drops, they often stay, drawn by wet food, uncollected rubbish and damp hiding places.

WHO, CDC and Thailand's Department of Disease Control all warn about animal-borne disease after floods, especially leptospirosis, and advise removing rodent food and shelter, cleaning droppings and urine correctly, and disinfecting contaminated surfaces.

One point must be clear from the start: disinfectant spraying is not rat or cockroach control. It deals with germs the animals leave on surfaces. Reducing the animals themselves requires removing food sources, sealing entry points and professional pest control alongside cleaning.

Example Case: A Market Grocery Covered in Rat Droppings After the Flood

Note: a typical scenario compiled from common post-flood situations, not a specific customer's account.

Nid runs a small grocery in a community market in central Thailand. When water stood in the shop for about a week, she moved stock to the top shelves and closed. On reopening, she found droppings scattered across the shelves, gnawed bags of rice and snacks, long dried urine trails along shelf edges and a sharp musky smell. At night, large cockroaches ran out of the drain behind the shop.

Her assistant swept the droppings with a dry broom, raising dust throughout the shop, then wiped the shelves with a damp cloth and restocked. A few days later he had a high fever, calf pain and red eyes. At the clinic the doctor asked whether he had waded through water or touched rat urine, treated him and advised that the shop be cleaned again properly, never dry-sweeping droppings.

Scenes like this play out in many shops and homes after floods. Knowing which germs rats and cockroaches bring, and how to clean safely, stops clean-up from becoming the moment of infection.

Ranking Criteria for Germs Spread by Rats and Cockroaches After Floods

This is an editorial ranking by World Health Disinfection (WHD), not an official list, and it uses no case statistics. We weighed:

• Link to floods in WHO, CDC and Department of Disease Control warnings, such as leptospirosis.
• Strength of the animal link: whether the animal is a direct source or a mechanical carrier.
• Route to people via surfaces: food, dishes, shelves, floors, dust and wounds.
• Severity and risk groups: children, older adults, pregnant women and people with chronic illness.
• How common it is in Thailand, described qualitatively.

Use the ranking to prioritise cleaning and watch for symptoms, not to diagnose. Anyone unwell should see a doctor.

No. 1: Leptospira, the Cause of Leptospirosis, from Rat Urine

Why first: rats are a key reservoir. Infected rats may look healthy but shed the bacteria in urine. When that urine mixes into floodwater, puddles or wet mud, the germ enters people through cuts, scrapes or the eyes, nose and mouth. Thai health authorities warn about leptospirosis after every flood, making it the clearest rat-and-flood germ.

Risk spots: yard puddles, under-house spaces, warehouses, storerooms, shelves with urine stains, around bins and drains.

Symptoms and risk: sudden high fever, headache, muscle pain especially in the calves and red eyes; some develop liver, kidney or lung complications. People who wade or clean without boots and gloves, or with cuts on hands and feet, face the highest risk. Anyone with fever after such exposure should see a doctor promptly and mention it.

Prevention: rubber boots and gloves, covering wounds, draining puddles, sealing food away and never handling urine-stained items bare-handed.

Cleaning and spraying: after food sources are removed and surfaces cleaned, spraying floors, shelves and rat paths reduces residual contamination. Leptospira falls in the bacteria group CHEMGENE HLD4H is stated to cover generally; WHD makes no organism-specific claim and will share data on request.

No. 2: Salmonella, Carried to Food by Both Rats and Cockroaches

Why second: rats can carry Salmonella in their guts and shed it in droppings, while cockroaches walking through sewage and rubbish can carry it on their legs and bodies to food and dishes. Linked to both pests and a major cause of food poisoning, it ranks high.

Risk spots: dry-food shelves, gnawed rice sacks, kitchen counters, upturned dishes, food cupboards and areas around bins.

Symptoms and risk: diarrhoea, fever, cramps, nausea and vomiting. Children, older adults, pregnant women and people with weak immunity risk dehydration and complications; see a doctor for high fever or persistent symptoms.

Prevention: discard gnawed food or anything with droppings, wash dishes before use, store food in sealed boxes and cook thoroughly.

Cleaning and spraying: WHD product information lists Salmonella among organisms CHEMGENE HLD4H is stated to cover. Spraying shelves, floors and walls around food storage after spoiled stock is removed and surfaces washed reduces what pests left behind.

No. 3: E. coli, Carried by Cockroaches from Drains to Counters

Why third: cockroaches live and feed in drains, sewage pits and toilets full of faecal bacteria. When they climb into kitchens after floods, they bring E. coli and other gut bacteria on their legs. Many studies have found a range of bacteria on cockroaches, which act as mechanical carriers moving germs from dirty places to clean ones.

Risk spots: counters, sinks, dish racks, chopping boards, under fridges and around floor drains.

Symptoms and risk: diarrhoea and cramps, sometimes bloody stools; young children and older adults dehydrate easily.

Prevention: cover drains at night, leave no food scraps in the sink, store clean dishes in closed cupboards and wipe counters before preparing food.

Cleaning and spraying: E. coli falls in the bacteria group the product covers generally; WHD makes no organism-specific claim and will provide data. Spraying around sinks, under cabinets and around pipes after cleaning targets cockroach routes.

No. 4: Shigella, a Dysentery Germ Cockroaches May Move onto Food

Why fourth: Shigella comes from human stool and causes illness in small doses. Cockroaches passing through toilets or sewer pipes are one possible route onto uncovered food, along with flies, which also increase after floods.

Risk spots: uncovered food, dishes left on tables, bathrooms and kitchens next to bathrooms.

Symptoms and risk: fever, cramps, frequent stools, sometimes with mucus or blood. Young children are most at risk; seek care immediately for bloody stools.

Prevention: cover food, wash hands after the toilet, wash dishes before use and remove wet rubbish daily.

Cleaning and spraying: Shigella falls in the bacteria group covered generally, with no organism-specific claim. Spraying bathrooms and kitchens after scrubbing reduces surface contamination.

No. 5: Staphylococcus, Klebsiella, Pseudomonas and Enterococcus on Cockroaches

Why fifth: besides gut bacteria, cockroaches may carry environmental and drain bacteria such as Staphylococcus aureus, Klebsiella, Pseudomonas and Enterococcus. These rarely sicken healthy people but matter for anyone with wounds, older adults and bedridden patients, which is important for homes caring for patients and small clinics.

Risk spots: patient rooms, wound-care supplies, bed sheets, bathrooms and areas near drains.

Symptoms and risk: infected wounds, boils, and urinary or lung infections in vulnerable people.

Prevention: cover wounds, keep dressings in closed boxes, change sheets often and seal gaps cockroaches use to enter patient rooms.

Cleaning and spraying: these belong to the bacteria group covered generally, with no organism-specific claim. Patients must leave the room during spraying and return at the technician's stated time.

No. 6: Hantavirus from Dust of Dried Rat Droppings and Urine

Why sixth: some rodent species carry hantaviruses and shed them in urine, droppings and saliva. People are infected by breathing dust stirred up from dried droppings or urine, for example while sweeping a storeroom. It is uncommon in Thailand, hence a middle rank, but it is the main reason CDC advises never to sweep or vacuum rodent droppings dry.

Risk spots: warehouses, storerooms, ceilings, roof spaces, long-closed cupboards and nesting areas.

Symptoms and risk: fever, muscle aches, headache and fatigue; some forms affect the kidneys or lungs. Those cleaning enclosed spaces with heavy droppings face the most risk and should see a doctor for any fever afterwards.

Prevention: air the space before entering, wear a mask, rubber gloves and goggles, soak droppings and urine with disinfectant for the time on the label, then pick up with paper or cloth into a sealed bag.

Cleaning and spraying: hantavirus is an enveloped virus within the virus group the product covers generally; WHD makes no organism-specific claim. Having protected technicians spray heavily soiled areas reduces the need for household members to handle them.

No. 7: Murine Typhus (Rickettsia typhi) from Rat Fleas

Why seventh: murine typhus is caused by a rickettsia with rats as the reservoir and rat fleas as the vector. People are infected when flea faeces enter scratches or wounds. It occurs in Thai urban areas where rats are common, and when rats move indoors after floods, their fleas may come too.

Risk spots: nests in ceilings, storage cupboards, piles of sacks, cardboard boxes and dark corners of shops and warehouses.

Symptoms and risk: fever, headache, body aches and sometimes a rash. Workers in rat-infested shops, markets and warehouses should see a doctor for a persistent fever.

Prevention: remove nests, seal entry points, discard nesting boxes and sacks, and use pest control when rats are numerous.

Cleaning and spraying: spraying disinfectant does not eliminate fleas or rats; prevention depends on rodent and flea control. Spraying is a supporting step after nests and contaminated materials are removed, to deal with other germs on surfaces.

No. 8: Rat-Bite Fever (Streptobacillus moniliformis)

Why eighth: this bacterium lives in rats' mouths and airways. People are infected through bites or scratches, or occasionally through food and water contaminated by rat excreta. It is uncommon, but after floods people move belongings and open cupboards where rats hide, raising the chance of a bite.

Risk spots: cupboards, drawers, piles of belongings and under beds during clean-up.

Symptoms and risk: fever, chills, joint pain and rash, sometimes after the wound has healed. Wash any bite or scratch with soap and clean water and see a doctor.

Prevention: wear thick gloves, tap dark spaces with a stick before reaching in, never handle rats bare-handed and keep children away from uncleared piles.

Cleaning and spraying: it falls in the bacteria group covered generally, but prevention relies on avoiding bites and controlling rats. Spraying reduces germs on surfaces rats touched after cleaning.

No. 9: Stomach Viruses Moved by Pests Across Surfaces

Why ninth: norovirus and hepatitis A come from human stool, not from rats or cockroaches. But cockroaches that cross toilets, sewer pipes and rubbish and then walk over food or dishes may be one route that moves contamination onto clean surfaces. The link is weaker than for higher-ranked germs, but worth knowing to protect food.

Risk spots: uncovered food, dishes, counters and food preparation areas.

Symptoms and risk: vomiting, diarrhoea, fatigue or jaundice with hepatitis A. Young children and older adults need attention to hydration.

Prevention: cover food, wash dishes before use, wash hands with soap and remove cockroaches from the kitchen.

Cleaning and spraying: WHD service and product information lists norovirus among covered organisms; hepatitis A falls in the virus group covered generally, with data available on request.

No. 10: Mold Spores and Cockroach Allergens in Damp Corners

Why tenth: this entry is different. Cockroach allergens are not germs but proteins from droppings, bodies and shed skins, and they are important triggers of asthma and allergies, especially in children. Combined with mold spores such as Aspergillus and Penicillium growing in damp corners after floods, the same corners cockroaches favour, these spots become a source of breathing problems at home.

Risk spots: under sinks, behind fridges, under-stair cupboards, storerooms and wet cardboard.

Symptoms and risk: blocked nose, sneezing, coughing and wheezing; asthma and allergy flare-ups. People with weak immunity should avoid moldy areas.

Prevention: discard wet cardboard, dry damp corners, use dehumidifiers, wipe cockroach droppings with a damp cloth rather than sweeping, and keep up cockroach control.

Cleaning and spraying: CHEMGENE HLD4H is stated to cover fungi, so spraying helps with surface mold after cleaning and drying. Allergens must be removed by physical cleaning, and WHD does not claim spraying removes them.

Why Sweeping, Plain Water or Insecticide Alone Falls Short

• Dry sweeping droppings raises contaminated dust you then breathe in.
• Plain water removes some residue but does not disinfect.
• Insecticide is not a disinfectant; dead cockroaches still leave germs and debris to clean up.
• Bleach needs correct dilution, must never be mixed with ammonia and is hard to apply evenly over large areas.
• Disinfecting without pest control lets rats and cockroaches return and contaminate again.

The effective order is: control pests, seal entry points, remove contaminated materials, clean correctly, then spray-disinfect surfaces.

Post-Flood Disinfection Spraying for Germs Left by Rats and Cockroaches

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

Please note: this is a disinfection service, not rat or cockroach extermination. Where pests remain numerous, arrange pest control first or alongside.

1. Survey: droppings, urine stains, gnaw marks and pest routes are mapped to set spray points.
2. Pest control and cleaning first: seal entries, discard contaminated food and materials, remove mud and clean residue correctly. Spraying follows cleaning and never replaces it.
3. Zoning: food stock and dishes sealed away; people, pets and plants leave the zone.
4. Spraying: shelves, floors, lower walls, around pipes, under cabinets and damp corners.
5. Re-entry: the service information says wait about 30 minutes, then use the space normally; follow the technician's time.

WHD does not claim zero residue, and spraying is not medical treatment. For lingering rat musk or musty odours, residential ozone disinfection is a complementary option.

10 Reasons Shops and Homes with Pest Signs Choose WHD

1. Spray points follow pest routes, droppings and urine stains.
2. Protected technicians handle contaminated areas instead of family or staff.
3. Medical-grade CHEMGENE HLD4H stated to cover viruses, bacteria and fungi.
4. Listed organisms include Salmonella, norovirus and fungi.
5. Mist reaches under cabinets, behind shelves and around pipes.
6. Endorsements from the Department of Medical Sciences, Mahidol University, NHS England and EN 14476.
7. About 30 minutes before normal use, per the service information, so shops can reopen quickly.
8. Honest about limits: spraying is not pest control.
9. Free CHEMGENE spray and WELLGIENIC wet tissues, plus tax invoices.
10. Ask WHD for test data on any organism.

Before and After Spraying

Example Case: Nid's Grocery After Tackling Pests and Germs

Note: a typical scenario, not a verified customer review.

Once her assistant recovered, Nid closed for two days and started over. A pest-control provider planned rat and cockroach control, gaps around pipes and under doors were sealed, all gnawed or soiled stock was discarded, water-damaged wooden shelves were replaced and food went into sealed plastic boxes. A spraying team then treated shelves, floors, the storeroom and the rear drain zone by zone while everyone waited outside. Afterwards the shop kept a new routine: drain covers closed every night, wet rubbish out daily and a morning check for droppings. Hesitant customers came back.

Checklist

FAQ: Germs from Rats and Cockroaches After Floods

Will spraying get rid of rats and cockroaches?

No. Spraying handles germs on surfaces; it is not designed to kill or repel pests. Seal entries, remove food sources and use pest control where needed.

Why must rat droppings not be swept dry?

Dry sweeping or vacuuming raises dust that may carry germs from droppings and urine. CDC advises soaking them with disinfectant for the time on the label, then picking them up with paper into a sealed bag.

Is food safe if rats only chewed the outer bag?

Do not take the risk; discard gnawed, soiled or urine-stained food. Undamaged sealed cans can be washed and wiped before opening.

I used insecticide. Do I still need to disinfect?

Yes. Insecticide does not disinfect, and dead cockroaches and droppings still leave germs and allergens. Remove them, clean, then spray.

Does the product cover Leptospira?

Leptospira falls in the bacteria group the product covers generally, but WHD makes no organism-specific claim. Contact WHD for test data.

Rats and Cockroaches Left Germs Behind? Let WHD Help

Ranking the germs spread by rats and cockroaches after floods shows that shelves, kitchens, pipes and storerooms come first. Once pests are under control and cleaning is done, let the team spray zone by zone.

Book Post-Flood Disinfection Spraying

Call 065-556-6294 | LINE @whd268

Related Services and References

• WHD Disinfection Spraying Service
• CHEMGENE HLD4H Disinfectant
• Residential and Building Ozone Disinfection

• Daily News, flood situation from the Department of Disaster Prevention and Mitigation, 5 October 2026: https://www.dailynews.co.th/news/6249374/
• CDC, Floods: https://www.cdc.gov/floods/
• CDC, Rodents: https://www.cdc.gov/rodents/
• World Health Organization, Fact sheets: https://www.who.int/news-room/fact-sheets
• Department of Disease Control, Thailand: https://ddc.moph.go.th/