A person recently swam and now has watery diarrhea, fever, cramping, and N/V. Which organism is most likely, and what is a treatment option?

• A. Cryptosporidiosis
• B. Giardiasis
• C. Salmonellosis
• D. Shigellosis

Answer: (A)

When you see watery diarrhea after a recent swim, think about a waterborne protozoal infection, with Cryptosporidium as a classic cause. The oocysts can contaminate pools and splash areas, and they’re unusually resistant to typical chlorine levels, so outbreaks can occur even in well-kept water. The clinical pattern often includes profuse watery diarrhea, abdominal cramps, nausea or vomiting, and sometimes fever, which fits the swimmer’s presentation.

Management centers on keeping the person hydrated and replacing electrolytes. For those with normal immune function, nitazoxanide is an approved option that can shorten illness. There are no reliable antibiotics for Cryptosporidium, and the illness can be more prolonged or severe in immunocompromised individuals, where supportive care and addressing underlying immune status are important. In contrast, Giardia usually causes greasy, foul-smelling stools with bloating and less fever, while Salmonella or Shigella infections tend to present with higher fever and often bloody diarrhea linked to food exposure.