Fiji's Ministry of Health has declared a measles outbreak in the Serua and Namosi areas.
It said there had been two confirmed cases and two suspected cases at the Wailali Settlement in Wainadoi.
One person was in hospital, and the other three had either recovered or were recovering at home.
Anyone who was at Navua Hospital on Tuesday evening, or the IMCI children's clinic on Wednesday morning, is being urged to contact medical officers.
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The ministry had activated its measles response plan, which includes isolating cases as well as training and vaccinating those who had contact with the cases and at-risk communities.
People are being urged to avoid non-essential travel to the outbreak area, and to ensure their children have received at least two doses of the measles vaccine.
Fiji is the third Pacific country to declare a measles outbreak, following Samoa and Tonga last month.
In response to those outbreaks - and the initial outbreak in New Zealand - the Fiji authorities have made vaccines free as it tried to stem the spread of measles.
