Evidence of epidemics
Evidence for epidemics in New Zealand is imprecise before 1872 because statistics on causes of death were not collected. Even after 1872 misdiagnosis and under-reporting were common. Doctors in the 19th century could not easily distinguish diseases with similar symptoms such as diphtheria, scarlet fever and measles. The cause of an infant death might be entered in official records as diarrhoea or ‘want of breast milk’, when typhoid was probably the real cause.
Māori deaths did not have to be registered with the government until the early 20th century, and even in the 1918 influenza pandemic hundreds of reported Māori deaths were not registered. Statistics for Māori births, deaths and marriages remained incomplete until the 1940s.
Rubella (German measles) was not a notifiable disease (one which had to be reported to public health services) and caused very few deaths, but it did cause foetal abnormalities, including deafness. Unusually large numbers of deaf children were born in New Zealand in 1899, 1939 and 1941–42, which suggests that rubella was prevalent in or just before those years.
Improvements in disease identification
With the advent of bacteriology (the study of bacteria in relation to disease) in the late 19th century, identification of many diseases became more precise. New Zealand’s adoption of the Bertillon index of diseases (a list of known diseases) in 1909 reflects this. Since then, laboratory techniques for identifying diseases and their effects on the human body have been vastly improved, which makes modern statistics for epidemics more reliable.
Monitoring infectious diseases in the 21st century
The Ministry of Health monitors infectious diseases and manages programmes designed to contain and minimise their effects. In an international context, the ministry works closely with the World Health Organization (WHO), providing it with New Zealand health statistics and other information.
The Immunisation Advisory Centre based at the University of Auckland provides independent, factual information on immunisation and vaccine-preventable diseases.
The Institute of Environmental Science and Research (ESR) monitors infectious diseases and provides information to the Ministry of Health on disease rates and distribution, identifies outbreaks, monitors interventions and predicts emerging disease hazards.