The parents of a 7-year-old child complain that their child for the last 2 days had body temperature of 38.8°C and sore throat. Objectively, catarrhal stomatitis is observed on the gums, cheeks, lips, and on the floor of the oral cavity. The submandibular lymph nodes are enlarged and painful. Bright-red catarrhal inflammation is present on the soft palate, tonsils, and palatine arches. The tongue is edematous, red, and dry. The skin of the face is hyperemic, except for the white nasolabial triangle. Make the provisional diagnosis: