Differential Diagnosis for Bad Diarrhea after Returning from a Cruise

Single Most Likely Diagnosis

• Norovirus infection: This is a common cause of outbreaks of gastrointestinal illness on cruise ships due to its highly contagious nature and the close living quarters on ships, which facilitate the spread of the virus.

Other Likely Diagnoses

• Vibrio infections (including Vibrio vulnificus and Vibrio parahaemolyticus): These bacteria can be found in seafood and contaminated water, which might be consumed during travel, especially if the water or seafood handling practices are not optimal.
• Salmonella or Shigella infections: These bacterial infections can be contracted through contaminated food or water and are known to cause diarrhea.
• Giardiasis: Caused by the Giardia lamblia parasite, this infection can occur through the consumption of contaminated water or food, and travel increases the risk of exposure.
• Food poisoning from other bacterial sources (e.g., E. coli, Campylobacter): Various bacteria can cause food poisoning, which could be contracted through improperly handled or cooked food during the cruise.

Do Not Miss Diagnoses

• Cholera: Although less common in travelers, cholera is a severe diarrheal disease caused by Vibrio cholerae, which can be life-threatening if not promptly treated. It's crucial to consider this diagnosis, especially if the patient has severe symptoms or if there was a known outbreak in the areas visited.
• Amoebic dysentery (Entamoeba histolytica): This parasitic infection can cause severe diarrhea and is more common in travelers to certain regions. It's essential to consider this diagnosis due to its potential severity and the need for specific treatment.

Rare Diagnoses

• Cyclosporiasis: Caused by the Cyclospora cayetanensis parasite, this infection can lead to prolonged diarrhea and is associated with the consumption of contaminated food or water, particularly in tropical regions.
• Cryptosporidiosis: This parasitic infection can cause diarrhea and is more commonly seen in immunocompromised individuals, but it can also affect healthy travelers who consume contaminated water or food.
• Yersinia enterocolitica infection: A less common cause of diarrhea, this bacterial infection can be contracted through contaminated food or water and might be considered in cases where other diagnoses have been ruled out.