BOISE, Idaho (AP) — A popular Boise, Idaho, music festival has been postponed until September amid growing concerns about the coronavirus outbreak.

Treefort Music Fest attracts crowds of more than 20,000 people each spring. This year more than 400 artists and bands were in the lineup for the week-long festival originally scheduled to begin March 25.

Treefort organizers made the announcement Wednesday.

Idaho has not had any confirmed cases of COVID-19, the illness caused by the new coronavirus, but nearby states have seen growing community spread. The announcement on Treefort came the same day the World Health Organization declared the illness a global pandemic and Washington state Gov. Jay Inslee announced a ban on events of more than 250 people in the Seattle area.

Other major music festivals have made similar decisions. The Coachella music festival in California, originally scheduled for April, was postponed until October. The two-week-long film and music festival South by Southwest in Texas was canceled last week.

Treefort officials said all tickets purchased for the March event will be valid for September, and customers can request refunds by emailing the festival.

Lori Shandro, festival co-founder, said the decision was tough but the community has always been organizers' top priority.

“In light of event cancellations around the globe and uncertainty about how this outbreak will impact Idaho, it was decided that postponing our festival is the best way to reduce unknown risk for our community,” she said in a prepared statement.

For most people, the new coronavirus causes only mild or moderate symptoms, such as fever and cough. For some, especially older adults and people with existing health problems, it can cause more severe illness, including pneumonia.

The vast majority of people recover from the new virus. According to the World Health Organization, people with mild illness recover in about two weeks, while those with more severe illness may take three to six weeks to recover.