Viral Pharyngitis (including COVID-19): This is the most likely diagnosis given the combination of sore throat, fatigue, and night sweats. Both COVID-19 and other viral pharyngitis can present with these symptoms, and the current pandemic situation makes COVID-19 a particularly plausible cause.

Streptococcal Pharyngitis (Strep Throat): This bacterial infection is a common cause of sore throat and can be accompanied by fatigue. While night sweats are less typical, they can occur, especially if the infection is severe or if the patient has a high fever.
Influenza: Influenza (the flu) can cause sore throat, significant fatigue, and night sweats, especially during flu season. The symptoms overlap significantly with both COVID-19 and strep throat.
Mononucleosis (Mono): Caused by the Epstein-Barr virus, mono can lead to sore throat, profound fatigue, and night sweats. It's more common in younger adults and teenagers.

Tuberculosis (TB): Although less common, TB can cause chronic sore throat, fatigue, and night sweats. It's crucial to consider TB, especially in individuals with risk factors such as immunocompromised status, recent travel to or from areas with high TB prevalence, or exposure to someone with TB.
Lymphoma: Certain types of lymphoma can present with systemic symptoms like fatigue and night sweats, along with sore throat if there is lymph node involvement in the neck.

Lemierre's Syndrome: A rare condition characterized by a bacterial infection of the throat (usually by Fusobacterium necrophorum) that can lead to sepsis and thrombophlebitis of the internal jugular vein. Symptoms can include sore throat, fever, and fatigue, but it's much less common than viral or streptococcal pharyngitis.
Human Immunodeficiency Virus (HIV) Acute Retroviral Syndrome: The initial infection with HIV can cause a variety of symptoms, including sore throat, fatigue, and night sweats, mimicking other viral illnesses. This diagnosis is important to consider in individuals with risk factors for HIV exposure.