A Minnesota baby with a mild case of the flu has attracted national attention after officials discovered the child had a rare strain of virus that normally affects pigs, not people.

The baby, who fell ill in October, was only the second person in five years known to be infected with a novel strain of influenza A (H1N2) that is typically found in swine herds, according to the U.S. Centers for Disease Control and Prevention (CDC).

Health officials have been on the alert for cases like this because of concerns about new viruses spreading from animals to humans, especially since the H1N1 outbreak in 2009.

But there's no sign that this virus poses a danger to the public, because no one else in the child's family got sick, said Dr. Aaron DeVries, medical director of infectious disease for the Minnesota Department of Health.

"We haven't observed any additional cases," he said of the six weeks since the child developed symptoms.

DeVries said the case came to light because of a routine surveillance program in which flu samples are submitted to the state for testing. When lab tests confirmed the unusual strain, state officials notified the CDC.

Last week, the CDC reported the Minnesota case, along with a similar one in West Virginia. Both involved children who were infected with unusual strains of swine flu. But because neither child had any known contact with the animals, the CDC speculated that "limited human-to-human transmission may have occurred."

DeVries said it's important to keep an eye on these cases as possible early warning signs of emerging infections. At the same time, he said, it's likely that improved surveillance is picking up cases that would have been missed in the past. "We're finding them ... because we're looking much harder," he said.

The Minnesota child, who was not identified, has since recovered, DeVries said.

Maura Lerner • 612-673-7384