How can a NON certified Nursing Assistant get certified?

I work for a major non-profit hospital in Virginia, as a Nursing Assistant. My hospital provided a 5 day class in Nursing Assisting, and the rest has been on the job training. They DO NOT certify anyone. Is there a state certification board I can go to and take an exam? Do I need to take an actual college course? I would like to do private duty on the side.
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