Musculoskeletal strain: This is the most common cause of upper back pain, especially in the absence of systemic symptoms like fever or cough. The colicky nature of the pain could be due to muscle spasms.

Costochondritis: Inflammation of the cartilage that connects the ribs to the sternum, which can cause sharp, stabbing pains in the upper back.
Scoliosis or thoracic spine degeneration: Although less common in a 37-year-old without a history of back problems, these conditions can cause upper back pain, especially if there's an acute exacerbation.
Gallbladder disease: While the patient denies GERD, gallbladder issues can sometimes refer pain to the upper back, especially if the pain is colicky and worsens after eating.

Pulmonary embolism: Although the patient denies cough and fever, pulmonary embolism can present atypically, especially in younger patients, and is a life-threatening condition that must be considered.
Aortic dissection: A tear in the aorta's inner layer can cause severe, tearing chest pain that may radiate to the back. It's a medical emergency.
Spinal infection or osteomyelitis: Infection of the spine, which can cause back pain, fever, and other systemic symptoms, although the patient denies fever.

Pancreatitis: Inflammation of the pancreas can cause severe upper abdominal pain that radiates to the back, but it's less common without a history of gallstones or alcohol abuse.
Thoracic spine tumor: A tumor in the thoracic spine can cause back pain, but it's relatively rare and usually accompanied by other symptoms like weight loss or neurological deficits.
Herpes zoster (shingles): Reactivation of the varicella-zoster virus can cause a painful rash, but the pain usually precedes the rash and is dermatomal, which might not fit the central upper back pain description unless it involves a specific dermatome.