On Monday, the number of confirmed cases of swine flu had risen by 224 from last Friday, but the Ministry says the actual number is much higher, as testing is carried out only in the most serious cases.
Health officials say they will provide a fuller indication of the impact of swine flu on Tuesday.
The virus has been linked to seven deaths in New Zealand so far.
Warning issued for Pacific community
The Ministry of Pacific Island Affairs has made the rare move of urging Pacific people to take steps to curb swine flu.
The ministry says figures for the H1N1 virus show a high number of the confirmed cases are Pacific people, and action is needed to stop it escalating further.
Health Ministry chief advisor on Pacific Health Dr Api Talemaitoga says people in the Pacific community may face a double burden of existing medical conditions and factors like overcrowding.
Dr Talemaitoga says people with diabetes, respiratory problems and asthma are more affected by both seasonal influenza and swine flu. He says many Pacific people also wait until the last moment to seek help.
The Counties Manukau District Health Board plans to step up communications with the Pacific community, to support the ministry's message.
Chief medical officer Dr Don Mackie says significant numbers of Pacific Islanders have been turning up ill at hospitals.
