An unrealistically optimistic belief that others are at greater risk than ourselves can reduce our willingness to enact healthy behaviours [20] . During pandemics, particular 'out-groups' may be vulnerable to discrimination [21] . Although respondents correctly identified groups such as the immunocompromised as at greater risk [22] , half our respondents saw the sexually active as at greater risk, almost a third of Malaysians suggested homosexuals were at more risk of infection. This may reflect a popular belief in Malaysia that homosexuals are likely to be already immunocompromised through infection with HIV/AIDS. The homeless were also perceived as at greater risk in both Malaysia and Europe. Political and health authorities need to be wary of increased stereotyping and prejudice towards particular societal groups during an influenza pandemic. Our Europe-only data suggested that individuals underestimate the threat of regular seasonal flu, while a quarter of our respondents incorrectly believed seasonal flu and swine flu symptoms were different, and that seasonal flu vaccination could help immunise against swine flu. Despite major media and governmental campaigns across Europe, there is obviously still a need for greater information with respect to symptom logy and immunisation against infection.