CODY, Wyo. (AP) — Wyoming health officials are investigating more than 30 pneumonia cases in a single county this year.

The Cody Enterprise reports that the earliest cases occurred in February but health officials found a spike in late April.

The Wyoming Department of Health is handling the investigation into the 31 cases. Officials say most of the people infected are elementary-aged children.

Pneumonia is a lung infection that can be caused by bacteria, viruses or fungi. Symptoms can include a cough, fever, chills and trouble breathing; they may be mild or become severe.