(Reuters) — A newly discovered type of immune system protein or antibody can neutralise H5N1 avian influenza and other, seasonal viruses.

Here are some facts about influenza:

Seasonal influenza kills between 250,000 and 500,000 people globally every year, according to the World Health Organisation. This includes 36,000 people in the United States alone.

A new strain of flu could cause a pandemic, a global epidemic that could kills tens of millions of people.

No one can say where or when this might happen but scientists are very worried about H5N1 flu, currently affecting birds in Asia, the Middle East, Europe and Africa.

H5N1 rarely infects people but it has killed 254 out of 408 infected since 2003.

The fear is it could mutate into a form that people easily transmit to one another, in which case it would spread rapidly.

Several drugs can fight flu but only if given within a day or two of symptoms beginning.

The new antibodies appear to work even three days after infection, the researchers said.