The Board finds that the Veteran has an undiagnosed illness manifested by flu-like symptoms, which represents a complete grant of the benefit sought on appeal.

The Board has not made a final determination on the claims of service connection for inguinal hernia, PTSD, joint pain, fibromyalgia, left knee disability, right knee disability, tinnitus, chronic fatigue syndrome, respiratory disability, sleep disorder, IBS, and headaches. The claims are remanded to obtain additional evidence and determine if these conditions are related to service.

The Board has determined that the AOJ did not obtain all necessary opinions regarding whether the Veteran's symptoms are related to an undiagnosed illness or medically unexplained chronic multisymptom illness (MUCMI). The claims for service connection for fatigue, fibromyalgia, left elbow disorder, right elbow disorder, and sleep disorder are remanded for further development.

The Veteran's claim for service connection for migraine headaches, as secondary to tinnitus, is granted. The claims for service connection for hearing loss disability and a disability manifested by shortness of breath other than chronic sinusitis and allergic rhinitis are denied. The claims for service connection for an intestinal disability (diverticulitis), fatigue, hypertension, neck disability, right upper extremity radiculopathy, left upper extremity radiculopathy, right shoulder disability, left shoulder disability, upper and lower back disability, right lower extremity radiculopathy, left lower extremity radiculopathy, right hip disability, left hip disability, right foot pain, left foot pain, gastroesophageal reflux disease (GERD), and an acquired psychiatric disorder are all denied.

The Board dismissed the Veteran's claims of service connection for attention deficit disorder and joint pain due to his death during the appeal process.