Differential Diagnosis for Diarrhea after Swimming in Ocean

• Single most likely diagnosis
  • Giardiasis: This is a common cause of diarrhea in individuals who have been swimming in contaminated water. Giardia lamblia is a parasite that can be found in ocean water, especially near areas with sewage or animal contamination.
• Other Likely diagnoses
  • Norovirus infection: Norovirus is highly contagious and can be spread through contaminated water, food, or person-to-person contact. Swimming in ocean water contaminated with norovirus could lead to infection.
  • Vibrio infection: Vibrio species, such as Vibrio vulnificus, can be found in ocean water and can cause diarrhea, especially in individuals with open wounds or compromised immune systems.
  • Cryptosporidiosis: Cryptosporidium is a parasite that can be found in contaminated water and can cause diarrhea in humans.
• Do Not Miss (ddxs that may not be likely, but would be deadly if missed.)
  • Vibrio vulnificus septicemia: While less common, Vibrio vulnificus can cause severe septicemia, especially in individuals with liver disease or compromised immune systems. This condition can be life-threatening if not promptly treated.
  • Marine toxin poisoning: Certain marine toxins, such as those produced by dinoflagellates, can cause severe gastrointestinal symptoms, including diarrhea. These toxins can be deadly if ingested in large amounts.
• Rare diagnoses
  • Schistosomiasis: Schistosoma species are parasites that can be found in contaminated water and can cause diarrhea, among other symptoms. However, this diagnosis is less likely in individuals swimming in ocean water, as schistosomiasis is more commonly associated with freshwater exposure.
  • Diphyllobothriasis: Diphyllobothrium latum is a parasite that can be found in contaminated fish and can cause diarrhea. However, this diagnosis is rare and typically associated with consuming undercooked or raw fish, rather than swimming in ocean water.