I have found a couple government sites that explain it, so I have pasted five of the most accurate writings on them. It starts out feeling like a fever pretty much. (I know - Never siphon water from a turtle tank, FYI...)

     The illness it causes, salmonellosis, typically includes fever, diarrhea and abdominal cramps.  In persons with poor underlying health or weakened immune systems, it can invade the bloodstream and cause life-threatening infections.

     Fever, abdominal cramps, and diarrhea (sometimes bloody). Occasionally can establish localized infection (e.g., septic arthritis) or progress to sepsis.

     The disease causes acute intestinal distress with sudden onset of headache, fever, abdominal pain, diarrhea, nausea, and sometimes vomiting.

     These symptoms, along with loss of appetite, can last for several days. Dehydration (extreme loss of body water), especially among infants, can be severe. Salmonella is an invasive organism that can escape from the intestine and be spread by the blood to other organs. It can become a chronic infection in some people, who may have no symptoms yet can spread the disease to others.

     Symptoms of Salmonella include diarrhea, fever, and abdominal cramps that develop 12 to 72 hours after infection. The illness usually lasts 4 to 7 days, and most persons recover without treatment.