Differential Diagnosis for Vomiting, Nausea, and Associated Symptoms

Single Most Likely Diagnosis

• Viral Gastroenteritis: This diagnosis is likely due to the combination of vomiting, nausea, upset stomach, and diarrhea. The presence of a fever at the onset, followed by periods of feeling better and then worsening, is consistent with a viral infection. The recent history of a sore throat and cough also supports a viral etiology.

Other Likely Diagnoses

• Influenza: Given the symptoms of fever (initially), sore throat, cough, headaches, body aches, and fatigue, influenza is a plausible diagnosis. The fact that the cough is worse in the morning and night and the presence of daytime and nighttime symptoms align with influenza.
• Strep Pharyngitis: Although the primary complaint is gastrointestinal, the intermittent sore throat could suggest strep pharyngitis, especially if the throat symptoms persist or worsen.
• Viral Pharyngitis: Similar to strep pharyngitis, viral pharyngitis could explain the sore throat and is often accompanied by other viral symptoms such as cough and fatigue.

Do Not Miss Diagnoses

• Appendicitis: Although less likely given the duration and fluctuating nature of symptoms, appendicitis can present with nausea, vomiting, and abdominal pain. It's crucial to consider this diagnosis due to its potential for severe consequences if missed.
• Food Poisoning: This could explain the gastrointestinal symptoms, especially if there was a recent consumption of contaminated food. The presence of diarrhea and vomiting supports this possibility.
• Inflammatory Bowel Disease (IBD): While less common, IBD (Crohn's disease or ulcerative colitis) could present with chronic gastrointestinal symptoms, including diarrhea, vomiting, and abdominal pain, especially if the symptoms persist or worsen over time.

Rare Diagnoses

• Cyclic Vomiting Syndrome: A rare condition characterized by recurrent episodes of severe vomiting lasting hours to days, with periods of normal health in between. This could be considered if the vomiting pattern is cyclic and other causes are ruled out.
• Gastroparesis: A condition where the stomach takes too long to empty its contents, which can cause nausea, vomiting, and feeling full after eating only a small amount of food. This is less likely but could be a consideration if other diagnoses are excluded and symptoms persist.