Viral Gastroenteritis: This is a common cause of nausea, especially if the onset is acute and there's a history of exposure to someone with similar symptoms or recent travel. The duration since June 8th could fit within the timeframe for a viral infection.

Food Poisoning: Similar to viral gastroenteritis, food poisoning can cause nausea and typically has a more rapid onset after consuming contaminated food.
Gastroesophageal Reflux Disease (GERD): Chronic nausea can be a symptom of GERD, especially if it's associated with eating or lying down.
Pregnancy: For female patients, nausea can be an early sign of pregnancy, often accompanied by other symptoms like vomiting and breast tenderness.
Medication Side Effect: Many medications can cause nausea as a side effect, so it's essential to review the patient's current medications.

Appendicitis: Although less common, appendicitis can initially present with nausea and vomiting before abdominal pain becomes more pronounced. Missing this diagnosis can lead to severe consequences.
Pancreatitis: Acute pancreatitis can cause severe nausea and vomiting, along with abdominal pain, and requires immediate medical attention.
Intestinal Obstruction: This is a surgical emergency that can present with nausea, vomiting, and abdominal pain. Early diagnosis is crucial to prevent complications.
Myocardial Infarction: In some cases, especially in women, nausea and vomiting can be symptoms of a heart attack, making it a critical diagnosis not to miss.

Brain Tumors: Rarely, brain tumors can cause nausea and vomiting due to increased intracranial pressure.
Meningitis: Inflammation of the protective membranes covering the brain and spinal cord can cause nausea, among other severe symptoms.
Addison's Disease: This rare endocrine disorder can cause chronic nausea, among other symptoms like fatigue and weight loss.
Porphyrias: A group of rare disorders that can cause acute episodes of nausea, vomiting, and abdominal pain, among other symptoms.