A 5-year-old boy presents with body temperature rise up to 39,2°C, sore throat, headache, nausea. Objectively: mucous membrane of soft palate and palatine arches is evidently hyperemic, there is distinct border between it and surrounding tissues. The child's tongue is dry, edematic, its lateral surfaces are red and free of fur, fungiform papillae are evidently enlarged. Face skin is covered with spotty rash, hyperemic except for pale nasolabial triangle. Submandibular lymph nodes are painful on palpation. What is the causative agent of this disease?