The Big Pair and Aleksei recovered first, followed by Anastasia and then Maria. Olga had the highest fever and pericarditis, Tatiana had abcesses in her ears, and Maria had double pneumonia. Anastasia and Aleksei presumably had run-of-the-mill measles.
When Kerensky visited, the Little Pair were still sick in bed, but Olga, Tatiana, and Aleksei were all well enough to meet him with their parents.