https://www.scientificamerican.com/article/cause-of-wuhans-mysterious-pneumonia-cases-still-unknown-chinese-officials-say/ > The cause of mysterious pneumonia cases in the Chinese city of Wuhan remains unknown, health authorities in the city said Sunday, as the number of infected people rose to 59 from 44 on Friday. > Seven of the sick are listed as critically ill, down from 11 on Friday. The number of close contacts of cases under medical observation has risen to 163.