Rod R. Blagojevich, Governor; Eric E. Whitaker, M.D., M.P.H., Director
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Protect your home against mosquitoes After the Flood Summer? No Sweat.



After a flood, the physical devastation to personal property and the community is obvious. These tragic consequences can be compounded by injuries or illness, though, if certain precautions are not taken to protect your personal health and safety. In addition to your physical health, you need take to time to consider your mental health as well. Remember, some sleeplessness, anxiety, anger, hyperactivity, mild depression or lethargy are normal. If these symptoms are acute or if they persist, however, seek some counseling.

This information is provided by the Illinois Department of Public Health to help flood victims protect themselves against diseases and other hazards in the days and weeks following a flood.



Following a flood, it can be difficult to maintain good hygiene and cleanliness.

Doing so is imperative, however, if the risk of disease is to be minimized.

One of the most important things you can do to prevent the spread of waterborne disease is to always wash your hands with plenty of soap and clean, warm, running water. This is particularly important —

  • before preparing or eating food, handling a baby, smoking, or any other activity that involves touching something that may enter a person's mouth (Adults should make sure children do the same.);
  • after toilet use;
  • after handling articles contaminated with floodwater or sewage.

When no regular safe water supply is available, use bottled, boiled or chemically disinfected water for washing hands (and brushing teeth).

Keep wash cloths and dish towels clean. Bacteria can remain on towels and cloths, so wash linen often with clean water and soap.

Parents need to take special care that their children follow these precautions. Do not allow children to play in floodwater or in areas that have been flooded. Wash their hands frequently, especially before meals. Contaminated toys should be disinfected in a solution of 1 ounce of bleach (1/8 cup) in 2 gallons of water.

Protective Clothing

When entering an area that is or has been flooded, it is important to wear protective clothing, such as boots, rubber gloves and long-sleeved shirts, to help reduce contact with contaminated items. Take care not to step on nails or other protruding items.


Floodwater may contain fecal material from overflowing sewage systems, and agricultural and industrial byproducts. While skin contact with floodwater does not, by itself, pose a serious health risk, ingesting anything contaminated with floodwater can cause disease.

Although disease outbreaks are rare after flooding, floodwater can contain various bacteria, viruses and other infectious organisms that may cause disease. If you are in a flood area and become ill, report your condition to your physician or local health department. The symptoms of most waterborne illnesses are similar — nausea, vomiting, diarrhea, abdominal cramps, muscle aches and fevers. Individuals may need to seek medical attention if these symptoms are severe or persist.

If you have any kind of cut, burn or infection on your hands, be sure to use plastic or rubber gloves if you must to be in contact with floodwater. If open sores become exposed to contaminated water, disinfect the area(s) with soap and clean water to control infection. If a wound develops redness, swelling or drainage, immediately seek medical attention.

One of the most serious problems that can arise from skin contact with floodwater is tetanus. The tetanus bacteria typically enters the body through places where the skin is broken, so it is very important to protect these areas. Anyone sustaining a puncture wound or who has a wound that becomes contaminated with feces, soil or saliva should have a doctor determine whether a tetanus booster is necessary. Specific recommendations for vaccinations should be made on a case-by-case basis.


Public and private water supplies may be contaminated in a flood. After a flood, consider all water unsafe. Listen for public announcements on the safety of your area's water supply and follow the instructions of local authorities.

Private water wells should be pumped out, allowed to recharge naturally, disinfected and the water tested before drinking or being used for cooking. If you need assistance in having your well water analyzed, contact the local health department in your area for information. In areas without local health departments, persons can contact the nearest Illinois Department of Public Health regional office.

The safest approach is to drink and cook with bottled water or water previously stored in the refrigerator. If you have to use tap water, boil it vigorously for at least three minutes. If you cannot boil it, add five drops of household bleach to each gallon of water. Mix thoroughly and allow to stand for 30 minutes. This method should be used only with water that is clean in appearance and free of odor.

Do not use contaminated water to make ice, brush your teeth or wash dishes. If there is a shortage of safe drinking water, use clean disposable eating utensils, plates and napkins.


Generally, do not eat any food that has come in contact with floodwater. If the safety of any food or beverage is questionable, follow this simple rule: When in doubt, throw it out.

Canned Goods

Carefully examine all canned and bottled goods that have been submerged or come in contact with floodwater. Some cans or bottles may be safe to use after a good cleaning. Follow these guidelines:

  • After being under water, containers with cork-lined lids or caps, screw tops or pop tops are nearly impossible to clean thoroughly around the opening. Any major temperature changes can actually cause contaminants to be sucked into such containers. They should be discarded.

  • If they appear undamaged, tin cans are usually safe. Wash in bleach water (1/4-cup bleach in 1 gallon of water) for one minute, then dry to prevent rusting.

  • If cans have pitted rust spots that cannot be buffed off with a soft cloth, contamination may have entered through corroded holes in the walls of the can. Discard these cans.

  • Cans with ends that bulge or spring in and out when pressed should be discarded immediately. This usually means bacteria are growing inside and producing gas that expands the can. Do not taste the contents of such cans.

  • If a can is crushed, dented or creased, closely examine it to see if it is safe to use. A dent may weaken the seam and allow contamination. If a dent or crease is very sharp, the contents may be contaminated. Discard these cans. Do not taste.

What To Do When Your Freezer Fails

When the electricity is off, a fully stocked freezer will keep food frozen two days if the door remains closed. A half-full freezer can keep foods frozen about one day. What can you do if electric service will not be reconnected within one or two days?

  • Keep the freezer door closed.

  • If your friends have electricity, divide your frozen foods among their freezers.

  • Seek freezer space in a store, church, school, or commercial meat locker or freezer that has electrical service.

  • Know where you can buy dry and block ice. Dry ice freezes everything it touches; 25 pounds of it will keep a 10-cubic-foot freezer below freezing for three to four days. When using dry ice, though, be sure to take several precautions. Never touch dry ice with bare hands! Also, do not stick your head into a freezer that contains dry ice. It gives off carbon dioxide, which replaces oxygen, so leave the door open a short time before examining your food.

  • If food is still "cold-to-the-touch," it may be cooked and eaten immediately, or refrozen.

What To Do When Your Refrigerator Fails

When power goes off in the refrigerator, you can normally expect food inside to stay safely cold for four to six hours, depending on how warm your kitchen is.

  • Add block ice to the refrigerator if the electricity is off longer than four to six hours.

  • High-protein foods (dairy products, meat, fish, poultry) should be consumed as soon as possible if power is not restored immediately. They cannot be stored safely at room temperature.

  • Fruits and vegetables can be kept safely at room temperature until there are obvious signs of spoilage (mold, slime, wilt). In fact, with good ventilation, vegetables will last longer at room temperature. Remove them from the refrigerator if electrical service may not resume soon.


Flooded indoor areas must be scrubbed with warm soapy water. Pay particular attention to food-contact surfaces (counter tops, pantry shelves, refrigerators, stoves, cutting boards, etc.) and areas where small children play. Then, rinse with a solution made by adding 1/2 cup (4 ounces) of laundry bleach to each gallon of water.

Wash all linens and clothing in hot water or have them dry cleaned. Items that cannot be washed or dry cleaned, such as mattresses and upholstered furniture, should be air dried in the sun and then vacuumed and sprayed thoroughly with a disinfectant. Steam clean all carpeting.

If there has been a back-flow of sewage into the house, remove and discard any absorbent household materials, such as wall coverings, cloth, rugs and sheetrock. Be sure to wear rubber boots and waterproof gloves during the cleanup.


After floodwaters recede, usually only minimal repairs may be necessary for a private sewage system to properly function. Outdoor toilets that have been flooded should be scrubbed thoroughly with a solution of 1/2 cup of laundry bleach per gallon of water. In the aftermath of a flood, most communities will provide portable toilets, but these may be limited.

If no toilet facilities are available, deposit body waste in a water-tight receptacle used for that purpose only. Place a small amount of water in the receptacle before it is used to make emptying easier. Dig a trench or pit and empty the contents of the receptacle into this pit as soon as possible after each use. Cover the waste in the trench after each use with a small layer of dirt, ashes or lime. Also, empty the water used to wash the receptacle into the pit or trench. When closing the trench, cover it with at least 12 inches of earth.


Gas Lines

When returning to your home, check immediately for leaking gas pipes. Do this by smell only. If you must have light, use battery-powered flashlights or lanterns. DO NOT turn lights on or off and do not use candles, oil or gas lanterns, or torches because, if gas lines are broken, an explosion could occur.

If you smell gas or suspect a leak, turn off the main gas valve at the meter, open all windows and leave the house. Notify the gas company or the police or fire department. Do not re-enter the house until you are told it is safe to do so.


Your electrical system also may be damaged. If you see frayed wiring or sparks, or if there is an odor of something burning, but no visible fire, you should immediately shut off the electrical system at the circuit breaker.

Consult your utility company before using electrical equipment, including power generators. Be aware that it is against the law and a violation of electrical codes to connect generators to your home's electrical circuits without approved, automatic interrupt devices. If a generator is on-line when electrical service is restored, it can be a major fire hazard. In addition, improperly connecting a generator to your home's electrical circuits may endanger line workers helping to restore power.

If any of your electrical appliances are wet, first turn off the main power switch, then unplug the appliance, dry it out, reconnect it and finally turn on the main power switch. If fuses blow when the electric power is restored, turn off the main power switch again and then inspect for short circuits in your home wiring, appliances and equipment. Caution: Do not do any of these things if you are wet or standing in water.

Outdoors, exercise extreme caution if you find yourself around power lines. Do not touch downed power lines, particularly those in water, or objects that are in contact with downed power lines.


The large amount of pooled water that remains after a flood provides an ideal breeding ground for mosquitoes. While the majority of these mosquitoes will be merely pests, some can carry communicable diseases.

To protect yourself from mosquitoes, you should —

  • Be sure door and window screens are tight-fitting and in good repair.

  • Wear long-sleeved and long-legged clothing.

  • Check to see that your mosquito repellent contains DEET, a chemical commonly found in these products. When outdoors, apply repellent sparingly to exposed skin or clothing, as indicated on the product's label.

  • Drain standing water in old tires, tin cans, bird baths, yard ornaments or other places where mosquitoes might breed.

Other Hazards

Swiftly Flowing Water

Do not enter swiftly flowing water, regardless of your ability to swim. You risk drowning even in swiftly moving shallow water. Do not rely on cars or other vehicles to protect you from floodwaters. People are more likely to drown inside a vehicle.

Even shallow standing water holds hazards. Small children can drown in standing water. You should avoid wading in standing water because it may hide glass or metal fragments.


Many wild animals are forced from their natural habitats by flooding. Take care to avoid these animals because they may carry rabies. Many domestic animals also are without homes after a flood. Remember, both wild and domestic animals are disoriented when displaced. Do not corner any animal. If an animal must be removed for safety reasons, contact your local animal control authorities.

Rats may be a problem during and after a flood. Secure all food supplies and have any animal carcasses in the vicinity removed by local animal control authorities or private rendering companies.

If you are bitten by any animal, seek immediate medical attention.

If bitten by a snake, first try to accurately identify the type of snake. If it is poisonous, seek medical care immediately so that the correct anti-venom may be administered.

Chemical Hazards

When returning to your area, be aware of potential chemical hazards you may encounter during flood recovery. Floodwater may have buried or moved hazardous chemical containers. These containers may harbor solvents or other industrial chemicals.

Propane tanks or drums, including those from gas grills, should not be moved. Contact your police or fire department for assistance.

Car batteries, when submerged in water, may still contain an electrical charge. They should be moved with extreme caution using insulated gloves.


To assist water well owners with disinfection, a 10-minute video titled How to Disinfect Your Water Well is available through local libraries and health departments.

Drilled Wells

  1. Using the table "How to Disinfect a Drilled Well," determine the amount of water in the well by multiplying the gallons per foot by the depth of the well in feet. For example, a well with a 6-inch diameter contains 1.5 gallons of water per foot. To determine the number of gallons in a well that is 120 feet deep, multiply by 120 (1.5 x 120=180).

  2. For each 100 gallons of water in the well, use the amount if chlorine (liquid or granules) indicated. For example, 180 gallons of water x 2 ounces of chlorine granules per 100 gallons of water=3.6 ounces of granules (use 4 ounces).

    Mix this total amount of liquid or granules in about 10 gallons of water. Be sure dry granules or tablets are completely dissolved before adding them to the well.

  3. Pour the solution into the top of the well before the seal is installed.

  4. Connect a hose from a faucet on the discharge side of the pressure tank to the well casing top. Start the pump. Spray the water back into the well and wash the sides of the casing for at least 15 minutes.

  5. Open every faucet in the system and let the water run until the smell of chlorine can be detected. Then close all the faucets and seal the top of the well.

  6. Let stand for several hours, preferably overnight.

  7. After you have let the water stand, operate the pump, discharging water from all outlets (turning on ALL faucets) until all odor of chlorine disappears. Adjust the flow of water from faucets or fixtures that discharge into septic tank systems to a low flow to avoid overloading the disposal system.


Diameter of Well
(in inches)
Per Foot
3 0.37
4 0.65
5 1.0
6 1.5
8 2.6
10 4.1
12 6.0

Amount of Disinfectant Required for Each 100 Gallons of Water

Laundry bleach (5.25% chlorine)....................................................3 cups*
Hypochlorite granules (70% chlorine)........................................2 ounces**

* 1 cup=8 oz. measuring cup ** 1 ounce=2 heaping tablespoons of granules

Dug or Bored Wells

  1. The amount of water in the well determines how much disinfectant (bleach or granules) is required. Use the table below to make calculations.

    To determine the exact amount of chlorine liquid or granules to use, multiply the amount of disinfectant indicated (according to the diameter of the well) by the depth of the well. For example, a well 5 feet in diameter requires 4½ cups of bleach per foot of water. If the well is 30 feet deep, multiply 4½ by 30 to determine the total cups of bleach required (4½ x 30=135); 135 cups=8.44 gallons (16 cups=1 gallon), so use 8½ gallons.

  2. Here is another example: A well 6 feet in diameter requires 4 ounces of chlorine granules or powder per foot of water. If the well is 40 feet deep, multiply 4 (ounces) by 40 (feet). This well, then, requires 160 ounces of granules or powder, or 10 pounds.

  3. Add this total amount of liquid or dry bleach to about 10 gallons of water. Splash the mixture around the lining or wall of the well. Be certain the bleach solution contacts all parts of the well.

  4. Seal the well top.

  5. Open all faucets and pump water until strong odor of chlorine is noticeable at each faucet. Then stop the pump and allow the solution to remain in the well overnight.

  6. After it stands overnight, operate the pump, discharging water from all outlets (turning on ALL faucets) until the chlorine odor disappears. Adjust the flow of water faucets or fixtures that discharge to septic tank systems to low flow to avoid overloading the disposal system.


Diameter of Well
(in feet)
Amount of 5.25%
Laundry Bleach
Per Foot of Water
Amount of 70%
Chlorine Granules
Per Foot of Water
3 1.5 cups 1 oz.
4 3.0 cups 2 oz.
5 4.5 cups 3 oz.
6 6.0 cups 4 oz.
7 9.0 cups 6 oz.
8 12.0 cups 8 oz.
10 18.0 cups 12 oz.

Driven Well

All that is necessary to restore a driven or sand-point well is to pump it out thoroughly.

If the well has a pit, pump out any water that has accumulated in it.

For additional copies of this handbook,
contact your local health department or write to —

Illinois Department of Public Health
Division of Communications
535 W. Jefferson St.
Springfield, IL 62761
TTY (hearing impaired use only) 800-547-0466