South Carolina health officials thought they successfully isolated a case of a dangerous strain of E. coli for 11 days until a second case emerged in an outbreak.

State Epidemiologist Dr. Linda Bell of the Department of Health and Environmental Control (DHEC) said as soon as the second case emerged they immediately linked the second case back to a Greenwood day care and urged testing of all employees and children at the Learning Vine.

Bell said, "We investigate every report of this kind of E. coli by conducting an interview. It's a five- or six-page questionnaire about what all you've eaten since before you got sick and whether you've been somewhere like a state fair".

Every year South Carolina typically reports just a few isolated cases of the dangerous bacteria. The bacteria can cause vomiting and severe diarrhea.

DHEC said scientists are yet not aware of the origin of the bacteria, but it is likely that it spreads from person to person through human waste instead of food.

According to the Department of Social Services' website, the day care was inspected last week and cited for a dozen violations, including problems with restrooms, diaper changing, sanitation and food safety.

Bell stated that the latest outbreak appears being restricted to the day care center. No additional cases were discovered since Monday, she said.

A laboratory reported the first case to the agency on May 18, and health officials immediately contacted the infected person.

DHEC checked across the state and saw no other cases until May 29. A child in Greenwood was diagnosed with a disease that damages red blood cells that clog the kidneys, and it can be caused by an E. coli infection, Bell said.