A 12-year-old child presents with temperature 38°C, chills, nausea, vomiting, delirium, and weakness. On the middle third of the face there is hyperemia in a butterfly-shaped pattern. Regional lymph nodes are enlarged and mildly painful. In blood: leukocytes - 12 × 109/l, lymphocytes 8.0×109/l, ESR - 26 mm/hour. What diagnosis should be made?