The Spread of Waterborne Illnesses

With Hurricanes Harvey, Irma, and Maria ravaging Texas, Florida, and Puerto Rico, respectively, the 2017 Atlantic hurricane season was one of the worst in recent history. In addition to hundreds of billions of dollars in destruction, these hurricanes combined claimed scores of lives.

Although the immediate effects of Category 5 hurricanes are shocking, resulting in floodwaters carry more insidious threats such as waterborne disease. A review of 548 outbreaks dating back to 1900 showed that 51% of these outbreaks were preceded by heavy downpours.

Aerial view of a flooded neighborhood in Houston, Texas after Hurricane Harvey
Win McNamee / Getty Images

Waterborne illnesses are transmitted via the fecal-oral route. Microscopic fecal particles make their way into water and food, thus spreading infection. After heavy flooding, sewage plants fail and release copious amounts of untreated waste.

Let’s take a closer look at five waterborne diseases: bacterial dysentery, cholera, enteric fever, hepatitis A, and leptospirosis.

Bacterial Dysentery

Dysentery refers to infectious, bloody diarrhea. Bacteria that cause dysentery include C. jejuni, E. coli 0157:H7, E. coli non-0157:H7 strains, Salmonella species, and Shigella species. E. coli 0157:H7 and E. coli non-0157:H7 strains and Shigella dysenteriae produce Shiga toxin. Shigella is the most common cause of dysentery, and like other pathogens can be detected using stool culture.

Common symptoms of dysentery include painful defecation, abdominal pain, and fever. Because bacteria invade the colon and rectum, pus and blood are also present in the stool. The bacteria can cause bowel ulceration. Moreover, bacteria can be spread to the blood—resulting in bacteremia, or blood infection. Patients who have weakened immune systems or are malnourished are at higher risk for bacteremia.

Dysentery is more severe than stomach flu—especially in children younger than 5 and adults older than 64. This infection frequently results in hospitalization and can be deadly.

When the cause of dysentery is unclear or the patient fails to improve with first-line antibiotic therapy, colonoscopy can aid with diagnosis. Computerized tomography can also be used to diagnose dysentery in more severe cases.

Dysentery is treated with antibiotics and oral or intravenous fluids. In children, Shigella, Salmonella, or Campylobacter infection is treated with azithromycin, ciprofloxacin, or ceftriaxone. In adults, dysentery is treated with azithromycin or fluoroquinolones.

The treatment of Shiga-toxin-producing E. coli 0157:H7 and E.coli non-0157:H7 strains with antibiotic is controversial. There are concerns that antibiotics will precipitate hemolytic-uremic syndrome by increasing Shiga toxin production. Hemolytic uremic syndrome is a deadly condition that affects the blood and the kidneys.


Cholera refers to acute diarrhea caused by certain strains of Vibrio cholerae. Cholera toxin is secreted by Vibrio cholerae, which activates adenylyl cyclase, an enzyme located in the epithelial cells of the small intestine, thus producing hypersecretion of water and chloride ion in the gut leading to profuse diarrhea. The volume of diarrhea can amount to 15 L a day! Severe fluid losses quickly result in hypovolemic shock, a very dangerous and deadly condition.

The watery diarrhea of cholera is gray, cloudy, and without odor, pus, or blood. This stool is sometimes referred to as “rice-water stool.”

Stool cultures and blood tests show evidence of cholera infection.

Even in areas of flooding, cholera is rarely found in the United States. Modern sanitation and sewage treatment have eliminated endemic cholera in the United States. All recent cases of cholera in the United States can be traced back to international travel.

Cholera ravages developing nations with poor water and sewage treatment, and is the scourge of famine, crowding, and war. The last big outbreak of cholera in the Western hemisphere occurred in the aftermath of the 2010 earthquake in Haiti. The Haitian outbreak killed thousands of people.

The cornerstone of treatment for cholera is a fluid replacement. In mild or moderate cases, fluid replacement can be oral. Intravenous fluid replacement is used with the more severe disease.

Antibiotics can be used to shorten the duration of cholera illness. These antibiotics include azithromycin, ampicillin, chloramphenicol, trimethoprim-sulfamethoxazole, fluoroquinolones, and tetracycline. Of note, multiple drug-resistant strains of cholera exist.

Although there is a vaccine for cholera, it’s expensive, not that effective, and not that helpful in managing outbreaks. From a public health perspective, the best way to deal with cholera outbreaks is to establish proper waste disposal and provide clean food and water.

Enteric Fever

Enteric fever is caused by Salmonella species of bacteria. Typhoid fever specifically refers to enteric fever caused by the strain Salmonella typhi. Salmonella passes into the body through the small intestine and invades the blood. The bacteria can then spread from the gut to other organ systems, including the lungs, kidney, gallbladder, and central nervous system.

In uncomplicated cases, enteric fever manifests as a headache, cough, malaise, and sore throat as well as abdominal pain, bloating, and constipation. Fever climbs in a stepwise fashion, and during recovery, body temperature gradually returns to normal.

Without complications, the fever will break and a person with an enteric fever will recover in a week or two. However, even after the fever breaks, a patient may relapse and become sick with enteric fever again.

Complications are deadly and include bleeding, intestinal perforation, and shock. About 30% of people with enteric fever who receive no treatment develop complications, and these people account for 75% of deaths due to enteric fever. In people who are treated with antibiotics, the death rate is about 2%.

Blood cultures can be used to diagnose enteric fever. Leukopenia, or a drop in white blood cells, is also diagnostic.

Because of increasing antibiotic resistance, fluoroquinolones are the antibiotic of choice for treatment of typhoid fever. Ceftriaxone, a cephalosporin, is also effective.

Although a vaccine for typhoid fever is available, it isn’t always effective. The best way to prevent typhoid fever is by ensuring adequate waste disposal and consumption of clean food and water.

Typhoid fever can be spread from person to person; thus, people with this infection shouldn’t handle food. A minority of people who are infected with Salmonella typhi become chronic, asymptomatic carriers and can spread disease if not treated for several weeks with antibiotics. Chronic carriers can also be treated with a cholecystectomy or gallbladder removal.

Hepatitis A

Although hepatitis A infection is usually transient and not deadly, symptoms of this infection are very uncomfortable. About 80% of adults who are infected with hepatitis A experience fever, abdominal pain, loss of appetite, vomiting, nausea, and later during the course of illness, jaundice.

Death due to hepatitis A is rare and usually occurs in people who are elderly or those with the chronic liver disease, such as hepatitis B or hepatitis C.

Symptoms of hepatitis A usually last fewer than eight weeks. A minority of patients can take up to six months to recover.

Hepatitis A is diagnosed with the aid of a blood test that detects specific antibodies.

No specific treatment for hepatitis A exists, and patients are advised to receive plenty of rest and adequate nutrition.

Fortunately, the hepatitis A vaccine is nearly 100% effective, and ever since its introduction in 1995, the frequency of infection in the United States has dropped more than 90%. The hepatitis A vaccine is recommended for children who are aged 12 months and older as well as adults belonging to high-risk groups such as those living in areas where hepatitis A is routinely spread.

Because infection with hepatitis A takes a couple of weeks to take hold, shortly after exposure, symptoms of infection can be prevented with a vaccine or immune globulin administration.

Although unrelated to natural disasters and flooding, in 2003 and 2017, two major outbreaks of hepatitis A occurred. The first happened in Beaver County, Pennsylvania, and was traced back to contaminated green onions served in a Mexican restaurant. The second took place in San Diego and—due to limited sanitation— the risk was pronounced among members of the homeless population. Together these outbreaks resulted in hundreds of hospitalizations and several deaths.


In recent years, leptospirosis has reemerged as a clinically relevant pathogen with outbreaks occurring on every continent. Leptospirosis is a zoonotic disease, which means that it is transmitted to humans by animals. It appears that leptospirosis can also be transmitted between two people.

Leptospires are thin, coiled, motile bacteria transmitted to humans by rats, domestic animals, and farm animals. Human exposure usually occurs via environmental exposure but can also occur secondary to direct interaction with animal urine, feces, blood, or tissue.

Leptospirosis is distributed globally; however, it is most common in tropical and subtropical regions. It’s estimated that leptospirosis affects one million people a year, with 10% of infected people dying of the infection.

In 1998, there was a leptospirosis outbreak in Springfield, Illinois, among triathlon competitors. These triathletes were infected after swimming in contaminated lake water. Apparently, heavy rainfall caused agricultural runoff into the lake.

Transmission of leptospirosis occurs across cuts, denuded skin, and mucous membrane of the eyes and mouth.

Leptospirosis presents with a wide range of symptoms. In some people, leptospirosis causes no symptoms and is thus asymptomatic. In mild forms, symptoms of leptospirosis include fever, headache, and muscle aches. Severe leptospirosis causes jaundice, kidney dysfunction, and bleeding; this triad of symptoms is referred to as Weil’s disease. Severe leptospirosis can also present with pulmonary hemorrhage, or bleed from the lungs, which may or may not be accompanied by jaundice.

Most people who are infected with leptospirosis recover. Death can occur in cases of advanced disease that involve renal dysfunction and lung bleeding. Elderly and pregnant patients are also at increased risk for death secondary to leptospirosis.

It’s important to treat leptospirosis with antibiotics to prevent organ failure. Patients should be treated as soon as possible before organ failure occurs. Leptospirosis can be treated with a broad range of antibiotics, including, ceftriaxone, cefotaxime, or doxycycline.

In addition to antibiotics, supportive care such as the administration of intravenous fluids is also necessary.

In cases of severe disease, kidney dysfunction needs to be treated with short-term dialysis. Patients with lung bleeding may need mechanical ventilation.

There is a leptospirosis vaccine for animals. Some adults have also been vaccinated; however, this is an area that requires further study.

A Word From Verywell

Even though the United States is a wealthy country with excellent sanitation and infrastructure, disasters—such as hurricanes and flooding—do happen. During these times of crisis, waterborne illnesses can spread.

Due to climate change and greenhouse gas emissions, climate modeling suggests that by the year 2100, there will be an increase in heavy precipitation events, which could contribute to the further dissemination of waterborne illnesses.

Verywell Health uses only high-quality sources, including peer-reviewed studies, to support the facts within our articles. Read our editorial process to learn more about how we fact-check and keep our content accurate, reliable, and trustworthy.
  • Pfeiffer M, DuPont HL, Ochoa TJ. The patient presenting with acute dysentery—a systematic review. J Infect. 2012;64(4):374-86.
  • Bernstein AS. Climate Change and Infectious Disease. In: Kasper D, Fauci A, Hauser S, Longo D, Jameson J, Loscalzo J. eds. Harrison's Principles of Internal Medicine, 19e New York, NY: McGraw-Hill; 2014.
  • Infectious Diseases. In: Iserson KV. eds. Improvised Medicine: Providing Care in Extreme Environments, 2e New York, NY: McGraw-Hill
  • Schwartz BS. Bacterial & Chlamydial Infections. In: Papadakis MA, McPhee SJ, Rabow MW. eds. Current Medical Diagnosis & Treatment 2018 New York, NY.
  • The Abdomen, Perineum, Anus, and Rectosigmoid. In: LeBlond RF, Brown DD, Suneja M, Szot JF. eds. DeGowin’s Diagnostic Examination, 10e New York, NY.

By Naveed Saleh, MD, MS
Naveed Saleh, MD, MS, is a medical writer and editor covering new treatments and trending health news.