Viral Conjunctivitis: This condition is characterized by hyperaemic eyes (redness due to increased blood flow), often accompanied by symptoms like fever, body pain, and running nose, which are indicative of a viral upper respiratory infection. The age and symptoms of the patient align well with this diagnosis.

Allergic Conjunctivitis: Although more common in younger populations, allergic reactions can occur at any age. Symptoms include itchy, red, and watery eyes, which could be accompanied by a running nose due to allergic rhinitis.
Bacterial Conjunctivitis: This infection can cause red, painful eyes with discharge. While it's less likely to be associated with systemic symptoms like fever and body pain compared to viral conjunctivitis, it's still a consideration, especially if the discharge is purulent.
Influenza or Other Respiratory Viruses: The symptoms of fever, body pain, and running nose could indicate an influenza infection or another respiratory virus, with the eye symptoms being secondary or coincidental.

Kawasaki Disease: Although rare in adults, Kawasaki disease can cause fever, conjunctivitis, and other systemic symptoms. It's crucial to consider this diagnosis due to its potential for serious cardiac complications if left untreated.
Temporal Arteritis (Giant Cell Arteritis): This condition, more common in older adults, can cause fever, headache, and visual disturbances, including conjunctival injection. It's a medical emergency due to the risk of vision loss.
Endophthalmitis: A severe, sight-threatening infection within the eye that can follow trauma, surgery, or bloodstream infection. Symptoms include severe eye pain, redness, and vision loss, which could be accompanied by systemic signs of infection like fever.

Relapsing Polychondritis: A rare autoimmune disorder that can cause conjunctivitis, among other symptoms like fever and arthralgias, due to its inflammatory nature affecting cartilaginous structures.
Sarcoidosis: A systemic granulomatous disease that can affect the eyes, causing uveitis or conjunctivitis, and is often accompanied by systemic symptoms like fever and fatigue.
Wegener's Granulomatosis (Granulomatosis with Polyangiitis): A rare autoimmune disorder that can cause a wide range of symptoms, including conjunctivitis, sinusitis, and systemic symptoms like fever and weight loss, due to its vasculitic nature.

Evaluation: A thorough history and physical examination, including ophthalmologic examination, are crucial. Laboratory tests may include complete blood count (CBC), blood cultures, and specific tests based on suspected underlying conditions (e.g., influenza testing, autoimmune panels).
Medication: Treatment will depend on the diagnosis. For viral conjunctivitis, supportive care with artificial tears and cold compresses may suffice. Bacterial conjunctivitis may require topical antibiotics. Systemic conditions like influenza may be treated with antivirals, and allergic conjunctivitis with antihistamines or mast cell stabilizers. For "Do Not Miss" diagnoses, specific treatments are available, such as high-dose aspirin and corticosteroids for Kawasaki disease, and corticosteroids for temporal arteritis.