People in Guernsey classed as "high risk" have been urged to get a flu vaccination.
Four islanders have been admitted to the Princess Elizabeth Hospital this week with flu-like symptoms, according to Health and Social Services.
Dr Brian Parkin, Guernsey's deputy medical officer of health, has advised elderly people and those with ongoing illnesses to contact their GPs.
A vaccine to protect against seasonal flu and swine flu is available.
People aged 65 and over, pregnant women, those with chronic health conditions and anyone caring for the elderly are advised to have the vaccination.
In Jersey, 11 people have been confirmed as having the H1NI swine flu.