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Dealing With Infection Risks In
The Home After A Flood

Advice Sheet issued by the International Scientific Forum on Home Hygiene

Jan 2005

This resource has been put together to provide advice and background information on cleaning up the home and post-flood decontamination of drinking water sources after floods. It also gives advice on treatment of water for domestic use during the flood.

1. A global problem

Flooding is the most common type of natural disaster worldwide, comprising forty percent of all natural disasters.

While the numbers of other types of natural disasters continue to decrease, the number of floods continues to rise.

Every year in South East Asia, hundreds of millions of people living in lowland river-line or coastal areas are affected by flooding. In the UK five million people live in places with a risk of flooding.

Quite apart from the devastation caused by the Tsunami in South East Asia, many countries around the world are often devastated by floods, particularly during the monsoon time:

In South East Asian countries like India, Bangladesh, Myanmar, Nepal, Laos, Vietnam etc monsoon floods & cyclones are almost annual phenomena

The 1999 cyclone in Orissa (India) killed 10,000 people and affected 10-15 million people.

In Bangladesh the devastating flood of 1991 & 1998 affected more than 30 million people, and the death toll was 140,000

The recent floods in China & Korea have made more than 2 million homeless           

Torrential rain and flooding hit the Dominican Republic and Haiti with drastic effects

In Prague, in 2002 more than 35,000 people were evacuated from their homes when the Vltava River burst its banks

In 2003, there was significant flooding in Florida and Jamaica following the hurricanes which hit the area.

2. Health risks after a flood

Floods present obvious health risks including drowning, electrical shock and starvation. Advice and fact sheets on what to do before a flood, once the flood arrives and after a flood can be found on the FEMA website.

Floods can also bring the risk of epidemic disease, which if not addressed appropriately can persist in the environment a long time after the flooding has ceased. This is exacerbated in hot climates. In the rural areas such as those in South
East Asian countries like Myanmar, Nepal, India, Bangladesh, Laos, Vietnam etc many or most of the tube wells/Dug wells which serve as sources for domestic water supply (both for private as also for public supply) get grossly contaminated with faecal matters during the floods. Unless they are thoroughly decontaminated (super chlorination) during the post flood situation, water borne infections like diarrhea, dysentery, typhoid, infectious hepatitis etc are likely to occur.

3. General guidelines for cleaning up and decontaminating water sources after a flood

Flood water affecting the home or other property is likely to be heavily contaminated with sewage and other organic material such as animal carcasses and therefore, it must be assumed that it is contaminated with human pathogens (germs). It may take a long time to dry out after flooding, especially in humid climates, and moulds can establish and grow on surfaces causing spoilage of items.
Thorough cleaning and disinfection is recommended on all surfaces affected. Ventilation is also important in order to assist the drying process.

Protect yourself from floodwater and other possible sources of germs as much as possible, particularly covering open cuts and wounds on exposed skin.

Waterproof dressings, rubber gloves and a mask to cover the nose and mouth are ideal if available.

It is advisable to wear rubber boots in case there has been a backflow of sewage into the house.

As soon as possible, remove and bury any faecal material from humans or animals to prevent spread of germs. The risk of spread of germs from residues of faecal material can be reduced by application of concentrated bleach solution*. This can also help reduce the infection risk to those involved in cleaning up the area.

As soon as possible, transfer all refuse to secure plastic bags or other containers to prevent the spread of germs until the refuse can be taken away.

Remove as much silt and water as possible from the home. Good ventilation and heating of the home will speed up the drying

Process, prevent mould growth and reduce the risk of spread of germs.

Remove and discard contaminated household materials such as soft furnishings and fittings that are damaged beyond repair eg.

Wall coverings, rugs.

For those items which are not irreparably damaged, but which cannot be washed or dry cleaned such as mattresses or upholstered
Furniture, air dry them in the sun and then, if there is no risk of colour damage, spray them thoroughly with a solution of bleach.

Steam clean all carpeting if possible.

Bedding, clothing and other soft / fabric articles including children’s toys etc should be laundered washing at 40-60°C with a bleach-based product (check ingredients on the package), or washing at 60°C or above (using any product as the higher temperature kills germs).

All hard surfaces should be hygienically cleaned either by cleaning followed by disinfection or by using a cleaner/disinfectant**. Be particularly careful to thoroughly disinfect surfaces that may come into contact with food, such as work surfaces, pantry shelves, refrigerators etc.
Areas where small children play should also be carefully cleaned and disinfected with bleach. Allow all surfaces to dry thoroughly good ventilation and heating will speed up the drying process.

When the surface is visually clean, clean again with a fresh solution of bleach in order to kill any remaining non-visible mould spores.

Allow all surfaces to dry thoroughly.

Any item that comes into contact with food such as crockery, cutlery, utensils and cooking equipment MUST be “hygienically cleaned before re-use.

If an adequate supply of hot water is available this can be done by detergent-based cleaning followed by thorough rinsing. Otherwise

The items should be cleaned and then disinfected by soaking in a solution of bleach**.

Do not be tempted to salvage foodstuffs. Any food item that has been in contact with floodwater should be regarded as contaminated and

Discarded. If it is not possible to reach shops, eat canned food provided that the can has not been punctured, corroded or damaged in any way and is not showing any signs of bulging or leakage.
Never use untreated floodwater for drinking, food preparation and cooking. Point of use treatment of the turbid floodwater to make it drinkable

Can be undertaken with a simple technique of coagulation, flocculation & disinfection.

Before treatment, remove any solid materials and filter through a cotton cloth.

Water sources must be thoroughly decontaminated to avoid the risk of water borne infections with Super Chlorination.
This can be achieved by adding chlorine to the water (in the form of bleaching powder (calcium hypochlorite) or bleach solution) and ensuring a contact period of 24 hours. The final concentration of chlorine in the water should be 25-50mgm/l available chlorine.

4. Useful sources of information.

a) On the IFH website

For comprehensive guidelines on how, when and where, hygiene should be applied in the home to prevent the spread
of infectious disease:

Guidelines for prevention of infection and cross-infection in the domestic environment: Focus on home hygiene issues in developing countries:

Recommendations for selection of suitable hygiene procedures for use in the domestic environment:

b) On the Internet


Why use Bleach?

Bleach contains hypochlorite. It is highly effective against viruses, bacteria, yeast and moulds. Bleach acts very quickly (within 1 minute) but longer times

 are required for killing moulds and fungi. Bleach is an excellent “cleaner” for even the toughest soils, and for the removal of mould growth. Bear in mind

 that chlorine-based bleaches can damage and/or bleach fabrics, carpets, soft furnishings and can corrode metal surfaces. Household bleach (both thick and thin bleach)

 for domestic use typically contains 4.5 to 5.0% available chlorine. Bleach/cleaner formulations (e.g sprays) are formulated to be used “neat” (i.e without dilution).

 It is always advisable however to check the label as concentrations and directions for use can vary from one formulation to another.

* Concentrated bleach

In situations where concentrated bleach is required, a solution containing not less than 4.5% or

45,000ppm available chlorine should be used.

**Hygienic cleaning of surfaces

Since flood water affecting the home or other property is quite likely to be contaminated with sewage, animal faeces, refuse etc it is important that all surfaces

are “hygienically cleaned” in order to get rid of germs as well as visible dirt. Hygienic cleaning of surfaces can be achieved in a number of ways according to the extent  of the contamination and the facilities available:

 Cleaning using detergent (liquid or soap) and hot water

Detergent and hot water cleaning can be used to produce a hygienically clean surface provided that the surface is then thoroughly rinsed using clean( potable) running water. Mechanical action using a cloth, sponge or brush to maximize removal of soil and microbes is an important part of the process. Removal of soil by wiping with a cloth without subsequent rinsing is not considered sufficient to achieve a surface that is hygienic. Use of a contaminated cloth can actually spread pathogenic organisms onto previously uncontaminated hands and hand and food contact surfaces.

If the surface is heavily soiled, clean thoroughly to remove the visible soil using a solution of detergent or soap. Using a clean cloth, apply a solution of bleach diluted to 0.5% or 5000ppm available chlorine to the surface. Since disinfectants are inactivated to a greater or lesser extent by the presence of soil, heavily soiled surfaces MUST be cleaned before application of a disinfectant.

If the surface is only “superficially” dirty, it may be hygienically cleaned using a combined bleach/cleaner containing 0.5% or 5000ppm available chlorine. The solution should be applied with a clean cloth or via a spray bottle and the surface then wiped. If necessary, repeat the process until the surface appears visibly clean.

*** Hygienic cleaning of laundry

Washing at temperatures of 40°C or less with a non bleach product is considered to carry a risk of inadequate decontamination. Laundry can be made hygienically clean by;

§         washing at 40-60°C with a bleach-based product (check ingredients on the package)

§         washing at 60°C or above (using any product as the higher temperature kills 

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