Updated

Hurricane Katrina is gone. But the disaster left in its wake continues to evolve.

Public health officials are still scrambling to find stranded people and treat the injured. In the immediate aftermath, aid workers are struggling to provide basic human needs: shelter, drinking water, food, clothing, and sanitation.

Also in short supply are the daily medicines needed by people with chronic illnesses such as diabetes and heart disease.

Disasters are humbling events. America is big, rich, and deep in resources. Yet the public health aftermath of Hurricane Katrina will continue for days, weeks, months, and years.

What can we expect as time goes by?

Contaminated Water

Floodwaters inevitably are contaminated with raw sewage. Even so, this water is not particularly dangerous unless a person drinks it or unless it gets into untreated wounds.

With water systems inoperative, sanitation becomes very difficult. Hand washing is the best way to prevent disease — but even hand washing is difficult in the absence of clean water. If available, alcohol-based hand sanitizers are very effective.

And water can be disinfected. This can be done by boiling water (a rolling boil for one minute) or, if boiling is impossible, by disinfection (1/8 teaspoon unscented chlorine bleach per gallon of clear water, 1/4 teaspoon per gallon of cloudy water; mix and let sit for 30 minutes).

One often overlooked source of contamination is bottled water from unsafe sources. If the source of bottled water is not known — especially if the seal on the bottle is not intact — it's a good idea to disinfect it.

Children's toys are also a source of contamination. If the toys come into contact with floodwater, they must be disinfected.

Once floodwaters recede, the risk of waterborne illness remains until municipal and home water systems can be fully disinfected. Most infections come from drinking water contaminated with fecal matter.

Waterborne illnesses have similar symptoms: diarrhea, cramping, fever, and/or vomiting. The specific symptoms — and their severity — depend on the type of illness and on the infected person's health. Common waterborne diseases in the U.S. include:

—Amebiasis

—Campylobacteriosis

—Cryptosporidiosis

—Giardiasis

—Hepatitis A

—Salmonellosis

—Shigellosis

—Viral gastroenteritis (such as norovirus and rotavirus infections)

The good news is that widespread disease rarely follows modern U.S. disasters.

Contaminated Food

In the days following a disaster, fresh food is in short supply. And with the power down, foods go bad very quickly. Any perishable food left out for more than two hours is unsafe. So is any food that has come into contact with floodwater.

Home-canned food that has come into contact with floodwater should not be eaten unless boiled. This holds true for all food containers with screw-top lids, snap lids, soda bottles, and other foods or beverages with crimped caps, flip-top, or snap-open tops.

Other canned foods can still make people sick if they come into contact with floodwater and are not disinfected before being opened. This means removing the label, washing the cans, and dipping them in a solution made of one cup of bleach and five gallons of water. It's a good idea to discard cans that have been tossed about by winds or water — their seals may have weakened and allowed contamination or spoilage.

Babies may become ill if fed powdered formula prepared with treated water. Only preprepared, canned baby formula is considered completely safe.

Mosquito-Borne Disease

With power down, windows open, and many people exposed to the elements, mosquitoes will have a field day.

Mosquitoes carry a number of diseases. West Nile virus season was just peaking when Hurricane Katrina hit.

Injuries

An injury seen after almost every disaster is carbon monoxide poisoning. The deadly gas comes from generators, cars and trucks, charcoal grills, camp stoves, or any other gas- or charcoal-burning device used in a poorly ventilated area.

Fallen power lines also tend to be killers. Power lines often lurk beneath floodwaters.

As power comes back on, generators attached to home electrical circuits pose a fire hazard as well as a danger to line workers trying to restore power.

People working in floodwaters often get injured by chain saws. They also risk electrocution if they operate plug-in electric power tools while standing in water.

Dead Bodies

In the aftermath of disaster, rescuing living people takes precedence over dealing with the bodies of those who have died.

Although it is counterintuitive, dead bodies do not pose an immediate health threat. It's hard to get an infection from the body of a person killed in a disaster. There's no hurry to bury the dead until every effort is made to identify the bodies and contact surviving family members.

Emotional Illness

Humans are remarkably resilient beings. But the trauma of a disaster pushes us to our limits.

Normal feelings include panic, feeling out of control, anger, despair, anxiety, and disorientation. On the other hand, there may also be unusually strong feelings of brotherhood, generosity, and caring for others. All of these powerful emotions are most likely to surface in the days following the disaster.

Those of us who lose loved ones will experience terrible grief. With time, this usually eases. But for reasons not fully understood, about one in 10 people who lose a loved one experience something called complicated grief. They get stuck in the grieving process and need professional help.

The single most important thing that lets people cope with a disaster is helping — or getting help from — other people. It's at least as true for children as it is for adults. This help includes:

—Simply being with others and talking about one's experience.

—Listening to others. Having answers is not as important as showing empathy. Crying is OK; it does not mean a person has "lost it," but that a person is processing strong feelings.

—Showing others you care through small deeds and sincere expressions of appreciation or empathy.

—Don't stop helping. A traumatized person's need for human contact continues for months. And it takes years to pull shattered lives back together.

By Daniel J. DeNoon, reviewed by Brunilda Nazario, MD

SOURCES: CDC. American Red Cross. University of Illinois Extension Disaster Resources. Pan American Health Organization. Randall D. Marshall, MD, director of trauma studies and services, New York State Psychiatric Institute.