Viral Gastroenteritis: This is the most common cause of acute gastroenteritis, characterized by fever, vomiting, and diarrhea. Viruses such as norovirus, rotavirus, and adenovirus are common culprits, and the symptoms typically resolve within a few days.

Bacterial Gastroenteritis: Bacteria like Salmonella, Shigella, and Campylobacter can cause similar symptoms. The presence of blood in the stool or a more severe course might suggest a bacterial etiology.
Food Poisoning: Consuming contaminated food can lead to symptoms of fever, vomiting, and diarrhea. The onset is usually rapid, and the duration is typically short.
Inflammatory Bowel Disease (IBD) Exacerbation: In patients with a history of IBD (Crohn's disease or ulcerative colitis), an exacerbation could present with these symptoms.

Appendicitis: Although appendicitis typically presents with abdominal pain, fever, and vomiting, diarrhea can occasionally be a symptom. Missing this diagnosis could lead to perforation and severe complications.
Intussusception: A condition where a part of the intestine telescopes into another, intussusception can cause vomiting, diarrhea, and fever, along with abdominal pain and potentially bloody stools. It's a medical emergency.
Septicemia or Bacteremia: Bacterial infections in the blood can present with non-specific symptoms including fever, vomiting, and diarrhea. Identifying and treating the source of infection is crucial.

Giardiasis: An intestinal infection caused by the parasite Giardia lamblia, which can lead to chronic diarrhea but may also present acutely with fever and vomiting.
Clostridioides difficile (C. diff) Infection: Typically associated with antibiotic use, C. diff can cause severe diarrhea, fever, and potentially life-threatening colitis.
Hemolytic Uremic Syndrome (HUS): A complication of certain bacterial infections (like E. coli O157:H7), HUS can present with diarrhea, vomiting, and fever, progressing to kidney failure and hemolytic anemia.