Viral Pharyngitis: This is the most common cause of sore throat in adults, often presenting with minor cervical adenopathy and without fever. The short duration of symptoms (24 hours) and the absence of fever also support this diagnosis.

Streptococcal Pharyngitis: Although less common than viral pharyngitis, streptococcal (strep) throat can present similarly and is a significant consideration due to its potential for complications if not treated. The presence of minor cervical adenopathy could be consistent with this diagnosis.
Acute Mononucleosis (Mono): Caused by Epstein-Barr virus (EBV), mono can present with sore throat, cervical adenopathy, and sometimes without fever, especially in adults. However, it often includes other symptoms like fatigue and may have a more prolonged course.
Allergic Pharyngitis: Allergies can cause throat irritation and minor cervical adenopathy, especially during peak allergy seasons. This would be more likely if the patient has a history of allergies.

Lemierre's Syndrome: A rare but potentially life-threatening condition that starts with pharyngitis and progresses to neck abscess and sepsis. It's crucial to consider this, especially if the patient's condition worsens or if there are signs of severe infection.
Epiglottitis: Although more commonly associated with severe throat pain and difficulty swallowing, epiglottitis can present atypically and is a medical emergency due to the risk of airway obstruction.
HIV Acute Retroviral Syndrome: In the early stages of HIV infection, patients can present with a flu-like illness that includes sore throat and cervical adenopathy. This diagnosis is critical to consider, especially in individuals with risk factors for HIV.

Diphtheria: A bacterial infection that can cause a severe sore throat and is characterized by a pseudomembrane on the tonsils or pharynx. It's rare in developed countries due to vaccination but should be considered in unvaccinated individuals or those traveling from areas where diphtheria is common.
Tuberculous Pharyngitis: A rare form of tuberculosis that affects the pharynx, often presenting with chronic symptoms. This would be more likely in individuals with a history of TB exposure or immunocompromised states.
Syphilitic Pharyngitis: Caused by Treponema pallidum, the bacterium that causes syphilis, this condition can present with a sore throat and is considered in individuals with risk factors for sexually transmitted infections.