SAN DIEGO -- San Diego's Health Department shut down a day care center Friday after at least one child tested positive for whooping cough.

Mary Duty, the owner and operator of Little Fingers Day Care in Spring Valley, said she had to turn away a dozen children Friday and then tell their parents they couldn't return until the kids had seen their doctor and started taking antibiotics.

"I have never seen a child cough that hard and that bad, and it was scary for me to see the child turning red, the colors in her face," said Duty.

Duty said the girl's whooping cough went undiagnosed.

"The doctors didn't do what they needed to do when the first child went to the doctor," said Duty.

Duty told 10News shutting down just one day will cost her $500. County health officials also asked that the carpet in her day care be professionally cleaned, which will cost her at least $100.

There have been about 300 cases of whooping cough in San Diego County so far in 2010, which is more than double the amount seen in all of 2009.

County health officials said it's on pace to have more whooping cough cases this year than in the last 50 years..