The city of Los Angeles on Wednesday approved an emergency measure to curb the spread of the nation’s most deadly West Nile virus outbreak by penalizing citizens who allow standing water on their property.

California now leads the nation with four fatal cases of the mosquito-borne virus, according to state health officials.

The bulk of the state’s 116 West Nile infections have occurred in southern counties, including Los Angeles and neighboring San Bernardino and Riverside.

Only Arizona has reported more human West Nile infections but its 274 cases have resulted in just two deaths, according to the Centers for Disease Control.

The Los Angeles City Council on Tuesday ordered the city attorney to draft an emergency ordinance to cite those with stagnant swimming pools or fountains, and to pay for a West Nile prevention campaign.

The measure is expected to receive final approval by the end of the month, a spokesman for Council Member Greig Smith, the ordinance’s sponsor, said.