All events with more than 250 people in King County will be prohibited following orders from state and local officials on March 11 in an attempt to slow the spread of COVID-19.

Gov. Jay Inslee announced at a press conference Wednesday morning that all events larger than 250 attendees will be banned in King, Snohomish and Pierce counties through the end of March. He said it will likely be extended beyond that.

It applies to all social gatherings, including church events, concerts and sporting events.

In addition, events smaller than 250 attendees will also be prohibited in King County unless organizers can meet certain criteria for social distancing and COVID-19 screening. County Executive Dow Constantine said he had directed the county’s Public Health Officer Jeff Duchin to sign the measure authorizing the restrictions. The orders went into effect on March 11 and there is no specific end date.

“Today’s actions will help relieve the strain on our hospital system,” Constantine said.

Under the order, an event is defined as a public gathering for business, social or recreational activities. It’s broadly interpreted, and includes community, civic, public, leisure or sporting events, parades, concerts, festivals, conventions and fundraisers. However, this is not a full list.

Grocery stores, retail businesses, drug stores, movie theaters and restaurants may continue to provide service as long as they follow the guidelines.

Organizers of events with less than 250 people must ensure that older adults and people with underlying medical conditions are encouraged not to attend, including employees. Social distancing recommendations must be met by limiting the time people spend within six feet of each other to 10 minutes or less.

Employees must further be screened for coronavirus symptoms each day, and excluded if they have symptoms. Further hand washing stations have to be available to all attendees and employees and enironmental cleaning guidelines from the Centers for Disease Control must be met. These include cleaning and disinfecting high-touch surfaces at least daily.

Inslee also directed school districts in coming days to develop contingency plans for school closures that could last weeks to months. Children have been relatively free of serious disease associated with the coronavirus outbreak, Inslee said, but they can still transmit it to other people.

Duchin said a severe outbreak is expected in coming weeks, which could go on for months. Snohomish County will also be mirroring King County’s guidelines on smaller events.

The goal of the measures is to reduce social interaction by at least 25 percent to slow the spread of the virus. Inslee said if left unchecked, infections across the state could reach 60,000 by mid-May.

Inslee said the guidelines would be “profoundly disturbing” to the way people live in the area today.

“These are not easy decisions,” he said.

As a result, the National Guard and State Guard were being mobilized to address the outbreak.

Last updated at 3:30 p.m.