The number of people admitted to hospitals with infectious diseases has more than doubled over the last 20 years, with children, elderly and lower socio-economic groups bearing the brunt of the diseases.
A study released by the University of Otago, Wellington shows hospitalisations from infectious diseases has increased by 51 percent over the two decades from 1998 to 2008.
Patients admitted were mainly from lower socio-economic areas of the country, and infections concentrated in children under five years old, and over 70 years old.
The bulk of the infectious diseases fell within the respiratory, skin and gastrointestinal categories, said lead investigator Associate Professor Michael Baker. Skin abscesses, cellulitis and pneumonia were the top three infectious diseases recorded.
The research also showed ethnic and income inequalities in infectious diseases were large and increasing. Maori and Pacific peoples were more than twice as likely as the European population to be hospitalised with a serious infectious disease, said Dr Baker.
"Fundamentally what this new research reveals is that the poorest sections of our community are bearing the brunt of an increasing burden of infectious disease, with children and older people in particular ending up in hospital; this is especially so for Maori and Pacific peoples.''
Those living in deprived neighbourhoods were almost three times the risk compared with those living in the most affluent areas.
Dr Baker said he was "taken aback'' by the size of the increase.
"What we expected to see was a steady incline in serious infectious diseases and a rise in admissions for chronic diseases, such as cancer and diabetes, which is the expected pattern for a developed country.
"Instead we found infectious diseases had rise far faster than chronic diseases. New Zealand now has the double burden of rising rates of both infectious and chronic diseases.''
The rates rose in uneven increments over the two-decade period. Dr Baker said the largest increase in infectious diseases occurred was in the 1990s, coinciding with a period of rapidly rising income and wealth inequalities associated with major restructuring of the New Zealand economy.
Dr Baker said the whole country was paying the price for the increase.
"These contagious diseases affect all sectors of society. The increased rates are adding 17,000 hospitalisations a year and tens of millions of dollars in avoidable health care costs.''
Nine authors worked together on the project for two years, collating data of hospitalisation records from District Health Boards across the country, said Dr Baker.
The study has been published in the international medical journal The Lancet.