A patient complains of fever up to 38°C, headache, pain in the joints anf muscles, vesicles in the oral cavity, mainly in the frontal part. Eating is sharply painful. For the last several years the disease has been recurring during wet and windy weather. The patient often suffers from cases of URTI. Objectively: on the buccal, lingual, labial mucosa there are con?uent erosions against the erythematous background, with gray-white coating. There are bloody scabs on the vermillion border and in the angles of the mouth. Make the diagnosis: