The World Health Organisation announced a pandemic of the AH1N1 swine flu this morning.
There have been 27 confirmed cases of the illness in New Zealand.
The ministry has advised people suffering symptoms of swine flu to contact the Healthline rather than visiting their doctor, in an attempt to help contain the disease.
This has resulted in an increase in the number of calls going to the centre.
A ministry spokeswoman told NZPA normal call levels were about 800 to 900 calls per day. Yesterday the team fielded over 1100 calls.
The staff were "coping well", the spokeswoman said.
"They've been gearing up for the greater volumes." There had been a lot of calls about swine flu as well as seasonal influenza.
Seasonal flu hits up to 20%, about 760,000, New Zealanders each year. On average, 2.7% of the population (156,000 people) will go to their GP because of flu each year and an estimated 95 people will die.