(CNN) Pigs at family-friendly fairs are responsible for infecting children with a type of swine flu not previously seen in humans, according to a report published by Thursday by the US Centers for Disease Control and Prevention. In August, the CDC confirmed variant swine flu viruses in 18 people -- 16 of them children -- who attended agricultural fairs in Michigan and Ohio. When a flu virus that normally circulates in pigs is found in a person, it is called a variant virus. The largest known outbreak of this same virus, referred to as influenza A (H3N2), occurred in 2012.The CDC confirmed variant swine flu viruses in 18 people in AugustTwo patients were hospitalized, but all recovered fully
The _ looked at all the samples from the 18 infected people. The report indicates that the _ is aware of these variant viruses and "keeping an eye on this," he said.