More travellers are returning to New Zealand with dengue fever with the mosquito-borne disease spreading in the region, health authorities say.
There have been 35 cases in Auckland so far this year, with 24 cases from Fiji alone.
Health services have advised people travelling to the Pacific to take steps to avoid mosquito bites.
Since October 2013, Fiji has recorded more than 10,000 cases of dengue fever, with 11 deaths.
Dengue fever has also emerged in French Polynesia, Vanuatu and New Caledonia.
The zika virus, which is similar to dengue, is widespread in French Polynesia, with cases also in New Caledonia and the Cook Islands, while another similar virus, chikungunya, has recently appeared in Papua New Guinea.
Anyone travelling to these countries is urged to exercise caution, Auckland Medical Officer of Health Dr Simon Baker said.
"Dengue fever can be a severe illness," he said.
"Those who travel to the Pacific frequently are at risk of repeat infections with different strains of the dengue virus. This can lead to dengue haemorrhagic fever, which can be fatal.
''This is heightened by the fact that, for the first time in 20 years, the dengue-three strain is active in the region."
Dengue fever symptoms begin with a high fever and severe headache. Nausea and vomiting are common, as are joint and muscle pain. The illness can last up to 10 days, although people can feel tired and depressed for weeks.
Zika and chikungunya cause similar, but often milder illnesses.
There was no vaccine for dengue fever, zika or chikungunya. The only way to prevent infection, Baker said, was to avoid being bitten by mosquitoes.
"Although the commonest time for bites is early morning and late afternoon, dengue-carrying mosquitoes also bite all through the day," he said.
The best protection from mosquito bites included wearing lightly-coloured clothing that covers your arms and legs, and a hat and shoes, applying insect repellent containing 40 per cent diethyltoluamide (DEET), to skin and clothing, and staying in accommodation that was air-conditioned, or had screens on doors and windows.
Anyone returning from overseas with dengue symptoms, or feeling generally unwell, should contact their GP or Healthline and let them know where they travelled, Baker said. Paracetamol was recommended rather than aspirin, because aspirin could increase the risk of bleeding.
New Zealand mosquitoes do not carry dengue virus, and it is not spread person to person.