A child, aged 4, has being ill for 5 days, suffers from cough, skin rash, t°- 38,2°С, facial hydropy, photosensitivity, conjunctivitis. On the face, neck, upper part of the chest there is bright maculopapular rash with areas of merging. Hyperemic throat. Seropurulent nasal discharge. In lungs there are dry crackles. What is the most probable preliminary diagnosis?