A 14-year-old girl complains of headache, nausea, fever of 39°C, chills, lumbar pain, and dizziness. It is the second day after the onset of the disease. Blood pressure 130/80 mm Hg. Blood test results: hemoglobin 128 g/L, erythrocytes 4.1012/L, leukocytes 14.109/L, ESR 27 mm/hour. Urinalysis results: specific gravity 1.010, leukocytes 20-35 in sight, erythrocytes 4-6 in sight, protein 0.099 g/L. What is the most likely diagnosis in this case?