Pacific Economic Ambassador Shane Jones and other New Zealand diplomats are being treated for suspected dengue fever after working in, or travelling to, Papua New Guinea.
The former Labour MP is in Middlemore Hospital in Auckland, where he says he feels ridiculous wearing sunglasses in bed.
The Ministry of Foreign Affairs and Trade (MFAT) confirms three employees are suspected to have contracted dengue fever while working in or travelling in PNG, but is not naming them.
"The staff members have been receiving appropriate medical treatment and we wish them a speedy recovery," a MFAT spokesman says.
Dengue is a mosquito-borne disease and MFAT staff posted to PNG or travelling to the region are all advised to take precautions.
Deputy High Commissioner Nicci Stilwell and Andrew Needs, the NZ-based head of the Pacific Division at MFAT, are believed to be the others affected.
A Defence staffer based in PNG is also understood to have been flown to Australia for treatment.
In 2014, MFAT introduced the new role of ambassador for Pacific economic development, which supports opportunities for Pacific countries to grow their income in sectors like tourism, agriculture, horticulture, and fisheries. Mr Jones was appointed to the role.
New Zealand contributes over $300 million in development funding to the Pacific annually.