Seven people have been diagnosed with a new kind of swine flu in California and Texas, the U.S. Centers for Disease Control and Prevention reported on Thursday.

All seven people have recovered but the virus itself is a never-before-seen mixture of viruses typical among pigs, birds and humans, the CDC said.

CDC officials are unsure whether the cases are related to an unusually late and severe flu season in Mexico in which 20 people have died.

It is genetically different from the fully human H1N1 seasonal influenza virus that has been circulating globally for the past few years. The new flu virus contains DNA typical to avian, swine and human viruses, including elements from European and Asian swine viruses.

SEVEN people have been diagnosed with a strange and unusual new kind of swine flu in California and Texas, the US Centers for Disease Control and Prevention reported.

All seven people have recovered but the virus itself is a never-before-seen mixture of viruses typical among pigs, birds and humans, the CDC said.

"We don't think this is time for major concern around the country."

However, some experts fear this strain, or another strain, could spark a pandemic that could kill millions.

"We believe at this point that human-to-human spread is occurring," Dr Schuchat said.

"That's unusual. We don't know yet how widely it is spreading.

"We are also working with international partners to understand what is occurring in other parts of the world."

SEVEN people have been diagnosed with a strange and unusual new kind of swine flu in California and Texas, the US Centers for Disease Control and Prevention reported.

All seven people have recovered but the virus itself is a never-before-seen mixture of viruses typical among pigs, birds and humans, the CDC said.

"We are likely to find more cases," the CDC's Dr Anne Schuchat said.

"We don't think this is time for major concern around the country."

However, some experts fear this strain, or another strain, could spark a pandemic that could kill millions.