Infectious mononucleosis and cold sores.
Infectious mononucleosis is caused by Epstein-Barr virus (EBV, human herpesvirus type 4), characterized by fatigue, fever, pharyngitis, and lymphadenopathy. Fatigue may persist weeks or months. Severe complications, including splenic rupture and neurologic syndromes, occasionally occur. Diagnosis is clinical or with heterophil antibody testing. Treatment is supportive.
Herpes labialis (cold sores) is an infection caused by the herpes simplex virus. It leads to the development of small and usually painful blisters on the skin of the lips, mouth, gums, or lip area. These blisters are commonly called cold sores or fever blisters.
Chlamydia, human papillomavirus (HPV), gonorrhea, herpes, hepatitis (multiple strains), and other sexually transmitted diseases (STDs)—including HIV—can be transmitted through oral sex.