While most people who contract swine flu will be able to recover at home, some people with other health conditions could become critically unwell and should phone a doctor, the Ministry of Health says.
That advice came after two people with swine flu were admitted to intensive care units in critical condition last week.
The ministry's deputy director of public health Fran McGrath said overseas, a number of swine flu cases had been reported in people who were fit and healthy and became very unwell.
Most people would be able to look after themselves but people whose symptoms worsened or who were more at risk, including pregnant women, people with respiratory disease, heart disease, liver disease or blood disorders, should contact their GP or phone Healthline on 0800 611 116, she said.
The total number of confirmed cases today reached 711, up 58 from 653 yesterday.
There were also 51 probable cases, down from 52 yesterday.
At 9pm yesterday, the World Health Organisation had recorded 70,893 cases in 190 countries, along with 311 deaths.
