notify_holders_and_above

notify_holders_and_above = {
	save_scope_as = infected_county
	if = {
		limit = {
			# Just so we don't fire multiple alerts for the Black Death
			scope:infected_county = {
				NOT = {
					any_county_province_epidemic = {
						intensity = apocalyptic
						epidemic_type = epidemic_type:bubonic_plague
					}
				}
			}
		}
		if = {
			limit = {
				scope:infected_county = {
					any_county_province_epidemic = {
						intensity = apocalyptic
						NOT = { epidemic_type = epidemic_type:bubonic_plague }
					}
				}
			}
			holder.top_liege = {
				trigger_event = epidemic_events.1101
				every_vassal_or_below = { #Toast notif
					limit = { 
						is_ai = no
						NOT = {
							is_target_in_variable_list = {
								name = plagues_notified
								target = scope:epidemic
							}
						}
					}
					add_to_variable_list = {
						name = plagues_notified
						target = scope:epidemic
					}
					send_interface_toast = {
						type = msg_epidemic_outbreak
						title = epidemic_events.alert_title
						left_icon = scope:infected_county
						custom_tooltip = epidemic_events.alert_description
					}
				}
			}
			holder = {
				if = {
					limit = { 
						is_ai = no
						notified_of_plague_trigger = no
					}
					trigger_event = epidemic_events.1101
				}
				every_liege_or_above = {
					limit = { 
						is_ai = no
						notified_of_plague_trigger = no
					}
					trigger_event = epidemic_events.1101
				}
				every_vassal_or_below = {
					limit = { 
						is_ai = no
						notified_of_plague_trigger = no
					}
					trigger_event = epidemic_events.1101
				}
			}
		}
		else_if = {
			# If it's minor we send you a toast unless it's in your domain
			limit = {
				scope:infected_county = {
					any_county_province_epidemic = {
						NOR = {
							epidemic_type = epidemic_type:bubonic_plague
							outbreak_intensity >= major
						}
					}
					holder = {
						this != top_liege
					}
				}
			}
			if = {
				limit = {
					holder.top_liege = { 
						notified_of_plague_trigger = no
					}
				}
				holder.top_liege = {
					send_interface_toast = {
						type = msg_epidemic_outbreak
						title = epidemic_events.alert_title
						left_icon = scope:infected_county
						custom_tooltip = epidemic_events.alert_description
					}
					add_to_variable_list = {
						name = plagues_notified
						target = scope:epidemic
					}
					every_vassal_or_below = { #Toast notif
						limit = {
							is_ai = no
							this != scope:infected_county.holder
							notified_of_plague_trigger = no
						}
						add_to_variable_list = {
							name = plagues_notified
							target = scope:epidemic
						}
						send_interface_toast = {
							type = msg_epidemic_outbreak
							title = epidemic_events.alert_title
							left_icon = scope:infected_county
							custom_tooltip = epidemic_events.alert_description
						}
					}

As written in game/common/scripted_effects/06_dlc_ce1_epidemics_effects.txt.