The current thinking is that although this is not known to have happened yet, it is possible. Scientists have only recently identified the H3N8 virus in US harbour seals, and they are concerned that this is very close to a form of avian flu that was discovered some years ago. This means that the virus may have jumped the species barrier, which always causes concern that it could do so again - especially since seals, like humans, are mammals.

This could be a similar case to swine flu - like pigs, seals can catch both bird and mammal viruses, which makes it easier for a new strain to evolve and possibly reach other animal groups.

However, now that the virus has been identified it should be much easier to deal with it. It was only last year that scientists noticed some puzzling deaths among seals in the northern US, which at first they thought were due to pneumonia. Now the cause is known, it will be possible to examine the virus more closely and learn more about its risks and how to reduce them.