Today's announcement comes after the Tulsa City-County Health Department said last week that four birds found in Tulsa had the mosquito-borne illness.
Now, 39 birds and eight horses statewide have tested positive for the disease this year. No humans have been infected so far but a Turpin man is being tested.
The virus killed two Oklahomans last year and infected 19 others. It usually causes flu-like symptoms but in rare cases can cause fatal brain inflammation.
Officials in Tulsa are spraying insecticide to control the mosquito population and say Tulsans should wear insect repellant and long-sleeve clothing outdoors.