Philadelphia Mayor Jim Kenney on Sunday issued a stay-at-home order for the entire city, his most dramatic effort yet to slow the spread of the novel coronavirus.

The order goes into effect Monday at 8 a.m. and prohibits public and private gatherings outside a single household, with certain exceptions, Philadelphia Managing Director Brian Abernathy said during a news conference Sunday.

Kenney said the was forced to issue the order because prior guidance telling people to stay home to slow the spread of the virus was not having the intended effect.