The researcher was infected while working with the virus in a laboratory, as part of the dengue fever eradication program said reports on Friday.

Chief Health Officer Dr Jeannette Young says they're not sure yet how he caught the bug, so safety precautions in the lab have been stepped up.

"We don't think he was bitten by a mozzie but we can't exclude it,'' she said on Friday. "The most likely scenario is that he's been infected by some of the dengue virus he was working with.''

The scientist was sick enough to be admitted to hospital but has been released. Dr Young says he's recovering well.

"Because we don't know how he got it, we've increased the use of personal protective equipment in that laboratory,'' she said.

"That means they'll wear the gear all the time - masks, double gloves, gowns, all those sorts of things...no one outside that lab is at any risk,'' she said.