Symptom	Potential illness or agent	Diagnostic test	Initiate urgent disease-specific therapy pending cultures?
Acute febrile illness after swimming in endemic area	Leptospirosis	Serologic testing	Yes, with doxycycline (outpatients) or ampicillin/sulbactam (Unasyn; inpatients)
Cellulitis (rapidly progressing) after exposure to salt or brackish water	Vibrio vulnificus sepsis	Blood culture, wound culture	Yes, with tetracycline (plus third-generation cephalosporin for hospitalized patients)
Diarrhea, any setting	Cryptosporidiosis, giardiasis	Stool studies	No, supportive treatment only
Diarrhea (bloody), any setting	Shiga toxin–producing Escherichia coli	Stool culture	No, symptomatic and supportive treatment only
Meningeal signs after exposure to infested fresh water	Primary amebic meningoencephalitis	Lumbar puncture	Yes, with miltefosine (Impavido, available from the Centers for Disease Control and Prevention)
Pneumonia after exposure to fresh water	Legionnaires' disease	Urine antigen test	Yes, with quinolone antibiotics