Last spring, a case was confirmed in Canada where the H1N1 flu virus was passed from a human being to a pig. Since then, there have been two similar cases reported in Norway, reports YLE.fi.

Research Professor Petri Ruutu of the National Institute for Health and Welfare says that the authorities in Finland have been aware of the cases in those two countries.

Concerning inocculation of pork farm workers, Professor Ruutu says that it must be kept in mind that establishing priorities for the vaccination programme required some tough decisions. The order in which different groups are being vaccinated is the result of cooperation among experts in a wide range of different fields.

"Restructuring priorities would be an unweildy process," says Professor Ruutu.

Influenza is basically a zoonosis, a communicable disease passed between animals and humans. However, that does not necessarily mean that all forms of influenza are easily passed from humans to animals.