Bacterial, viral, algal and protozoan infections are common after exposure to contaminated water. Swimming in ponds, lakes and oceans that are near developed areas may increase your risk of exposure to waste-water contamination if the areas have inadequate or overburdened sewage or waste-water treatment facilities. See a physician immediately on onset of fever after swimming, especially if traveling outside the United States.
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Leptospirosis is an infection caused by corkscrew-shaped bacteria of the genus Leptospira, which is passed through feces and urine of affected mammals and is characterized by fever, chills and intense headache. Researchers from the Robert Koch Institute in Berlin identified a case of leptospirosis in a triathlon athlete after he completed the swimming portion of the event in the Neckar River outside Heidelberg. Medical teams attempted to contact all of the participants to determine the risks of a possible outbreak. Of the 142 participants who responded, five more cases were confirmed. The authors said that heavy rains preceding the event most likely led to contamination of the water and that open wounds were probably the point of entry of the bacteria.
Enteroviruses are intestinal parasites that can contaminate water through human feces and cause a variety of illnesses, including meningitis, an inflammatory condition of the brain and spinal cord marked by sudden fever, paralysis and an altered mental state. An article in the September 2008 issue of “Clinical Infectious Disease” described an outbreak of viral meningitis among a school group returning from a trip to Mexico. Of the 29 travelers, 21 became ill four days after an extended swim in the Gulf of Mexico. Test results confirmed viral meningitis, and statistical analysis showed that the time spent swimming was positively correlated to the occurrence of the infection. The researchers concluded that the group was likely swimming in sewage-polluted seawater.
Lyngbya majuscule are a type of algae that bloom in tropical seawater and release toxins that cause illnesses marked by skin rashes, gastrointestinal disturbance, headache and fever. An April 2003 article in “Environmental International” assessed the health of swimmers at Moreton Bay, Australia, during an algal bloom. Researchers mailed 5000 residents questionnaires on recreational water activities and the occurrence of illness. Of the 1350 respondents, 78 percent reported being in the water at the time of the bloom and 34 percent of those reported one or more symptoms, with skin irritation the most frequent. Although a relatively large number of respondents reported symptoms of algal toxicity, only 29 appeared to be serious.
A study in the April 2005 issue of the “Journal of the Medical Association of Thailand” reported a case of a man's complaining of a low-grade fever, headache and bloody mucus in nasal discharge lasting for one week. Physicians found that he had been swimming in a natural pond two to three days before the onset of symptoms. Microscopic examination of the nasal discharge revealed the presence of two types of flagellated amoeba: the Naegleria and Acanthamoeba species. The authors concluded that this was the first report of a double infection of free-living amoeba in a live patient.