MINNEAPOLIS -- Concern, but not alarm. Not yet.

That's how Dr. Gregory Poland, the head of the Mayo Clinic's Vaccine Research Group, sums up his reaction to thediscovery of the H7N9 influenza in China.

"If we were to see cases outside of China or in the US, or evidence of human-to-human transmission, then I think it would be justified for us to be very concerned," Dr. Poland told KARE.

Poland was among the experts who appeared at a conference onvaccines and preventable diseasesFriday at the Minnesota Landscape Arboretum in Chaska.

"Right now they're in the very early stages, as they say, shoe leather epidemiology," he explained.

"Trying to learn where is the virus, how is it spreading and isolation of people who are infected."

As of Fridayat least 43 people had become infected with the H7N9 strain of the bird flu in China, and at least a dozen had died as a result of it.

Researchers suspect the virus spread from wild birds to domestic birds, and then to pigs, and possibly back to birds. But it's not known yet exactly how it has been transmitted to humans.

"Not all of them have had direct poultry contract, or are not poultry workers," Poland said.

"So where did they get it? it's really important to define what species did this come from, or come through."

One of the troubling aspect with the new form of the flu, in contrast with the H5N1 influenza, is that infected birds aren't falling from the sky.

"It was easy with H5 because you'd see birds dying," Poland said, "but H7 doesn't cause death in birds."

He said some of those infected with the H7 have responded to anti-viral drugs, which is a positive development. Specialized vaccines, on the other hand, may take months to create and produce in large quantities.

Poland said what's happening in China has all of the features of a pandemic, with the exception of human-to-human transmission.

"It's a novel virus, which means we haven't seen this one before andpeople don't have immunity to it," he said.

"If itspreads rapidly person to person thenyou'd call it a pandemic."

The Centers for Disease Controlin Atlanta has already advised medical providers in the US to look for signs of H7N9 in patients who have traveled to China recently, or are visiting from that nation.

Kris Ehresmannof the Minnesota Dept of Health said the MDH is encouraging anyone who has recently traveled to China, and is feeling sick, to see a doctor.

Doctors and hospitals are advised to take throat swabs of those patients and submit them to the CDC for analysis.

On Friday the CDC received its first sample of the virus from China.

So far there are no travel advisories have been issued.