A doctor is warning holidaymakers travelling to Asia and the Pacific to take proper protections against dengue fever.
Dr Joan Ingram said the number of cases of the mosquito-borne disease reported in New Zealand had increased nearly fivefold, to 54, in the three months to February compared with the same period two years ago.
Environmental Science & Research said in its latest report that all 32 dengue cases notified in the last quarter of last year had travelled or resided overseas during the incubation period of their illness.
The increase in New Zealand cases mirrors in a small way the large outbreaks occurring in a number of countries where the mosquitoes and dengue fever are common. Since October last year, Fiji has recorded more than 10,000 cases of dengue fever and at least 11 deaths from the disease.
Dr Ingram, an Auckland infectious diseases physician, said the case numbers and the geographic spread of dengue had risen in the past decade, with big outbreaks in Southeast Asia and Latin America.
"Even Singapore, with its fantastic efforts at mosquito control, had an outbreak last year. Now the Pacific is seeing increased numbers of cases, particularly in Fiji, but also in French Polynesia, Vanuatu [and] New Caledonia ... This has led to an increase in cases being diagnosed in people who have returned home with it.
"Some people believe that eating vitamin B or eating lots of Marmite reduces mosquito bites. It's a bit of a myth. There may be some reduction in the itch."
Dr Ingram said the mosquitoes that carried the dengue-causing virus were prevalent throughout most of the Pacific and she urged travellers to use insect repellents containing Deet or picardin, and protect their skin with clothing.
"The Aedes mosquitoes bite during the day - particularly early morning and late afternoon. They can lurk indoors in dark, cool places such as under beds, so try and stay in screened or air-conditioned rooms and spray your rooms."
Two other mosquito-borne viral diseases are also causing problems in the Pacific.
"Zika, an unusual virus previously only seen in Africa and Asia, has been causing illness in French Polynesia since October last year," said Dr Ingram. "It is usually a mild illness, only lasting a few days and causing fever, headache, conjunctivitis, rash and possibly joint and muscle pain ... there have been some neurological complications in some cases."
"Chikungunya fever, also initially from Africa, causes a similar illness to dengue, but with prominent joint pains. This can be severe."
Dengue fever is caused by a virus transmitted by bites from Aedes mosquitoes.
*No vaccine available and no specific treatment.
*Best protection is to avoid bites: Deet insect repellent, long clothing.
*Typical incubation period 7-10 days.
*Symptoms can include high fever, severe headache, rash, muscle and joint pain.
*Acute illness usually lasts up to 10 days. Full recovery can take weeks.