A sixth child has died in the United States from puzzling liver inflammation—aka hepatitis—and the number of unexplained cases has risen to 180 across 36 states, according to the Centers for Disease Control and Prevention.

The latest death was announced in a press briefing Friday, led by CDC Deputy Director for Infectious Diseases Jay Butler, who said it was reported to the agency Thursday. He did not indicate in which state the death occurred.

In addition to the deaths, 15 of the 180 cases required liver transplants, Butler reported. The cases all occurred in children under the age of 10 but skewed to preschool-age children, with the median age being around 2 years.