The Netherlands is experiencing a bizarre uptick in pneumonia cases among children, marking the second country to report an outbreak of this type this week.

The Netherlands Institute for Health Services Research (NIVEL), a research institute in Utrecht, around 25 miles south of Amsterdam, reports that 80 of every 100,000 children between ages 5 and 14 came down with pneumonia last week.

This is the largest outbreak of pneumonia NIVEL has recorded in recent years. At the peak of the 2022 flu season, when pneumonia cases were most common, there were 60 recorded cases for every 100,000 children in the age group.