Viral Gastroenteritis: This is often the most common cause of acute nausea, especially if Ed has been exposed to someone with similar symptoms or has recently traveled. Viral gastroenteritis can cause sudden onset of nausea, vomiting, and diarrhea.

Food Poisoning: Consuming contaminated or spoiled food can lead to acute nausea and vomiting. This is a common issue and can be related to eating at a new restaurant, consuming undercooked meat, or eating expired food products.
Motion Sickness: If Ed has been traveling by car, boat, plane, or any other vehicle, motion sickness could be a likely cause of his nausea.
Medication Side Effect: Many medications can cause nausea as a side effect. If Ed has recently started a new medication, this could be a contributing factor.

Appendicitis: Although less common, appendicitis can present with nausea and vomiting, especially if accompanied by abdominal pain. Missing this diagnosis could lead to severe complications, including perforation of the appendix.
Urinary Tract Infection (UTI) or Kidney Stone: In some cases, a UTI or kidney stone can cause severe nausea and vomiting. These conditions require prompt medical attention to prevent complications like sepsis or kidney damage.
Meningitis: This is an infection of the protective membranes covering the brain and spinal cord. Nausea and vomiting can be symptoms, along with headache and fever. Meningitis is a medical emergency.

Brain Tumor: Although extremely rare, a brain tumor can cause nausea and vomiting, especially if it's putting pressure on certain areas of the brain.
Gallbladder Disease: Gallstones or cholecystitis (inflammation of the gallbladder) can cause nausea, especially after eating fatty foods.
Inflammatory Bowel Disease (IBD): Conditions like Crohn's disease or ulcerative colitis can cause chronic nausea but can also have acute exacerbations.