Improved sanitation and water supplies virtually eliminated the major bacterial diseases of the 19th century from New Zealand’s European population by the 1920s. Epidemic diseases were no longer major causes of death. Non-communicable diseases such as cancer and heart disease replaced them as the leading causes of death.
Polio is probably a very old disease – a 3,500-year-old Egyptian wall carving shows a man with the characteristic withered leg of a polio victim.
Apart from isolated outbreaks of diphtheria and typhoid, and continued high death rates from tuberculosis, the most alarming infectious disease of this era was poliomyelitis (polio), an acute viral disease affecting the spinal cord and nervous system. Symptoms include fever, headache, malaise, pain and stiffness in back and neck, and partial or complete paralysis of limbs or the entire body. Case-fatality rates from paralytic polio have varied from 2% to 10%. New Zealand experienced polio epidemics in 1916, 1925, 1927, 1937, 1948–49, 1952–53 and 1955–56.
Polio is typically a disease of children and adolescents, but the risk of paralysis increases markedly with the age of the patient, making young adults especially at risk if they catch this disease. In early outbreaks there was no effective treatment so careful nursing and palliative care (which alleviates symptoms rather than the cause) were the main medical responses. The lives of seriously paralysed patients could only be saved by long periods in a compression chamber or ‘iron lung’. Survivors with a withered leg were fitted with strengthening callipers, which helped them walk. Public health campaigns in the 1950s stressed personal hygiene – schools provided buckets of disinfectant in their toilet blocks.
Effective polio vaccines were developed in the 1950s. Jonas Salk’s inactivated vaccine of 1955 was followed by Albert Sabin’s weakened live virus oral vaccine in 1960. In New Zealand use of the Salk vaccine delayed the reappearance of polio between 1956 and 1961. After this a mass immunisation campaign using the Sabin oral vaccine achieved high population coverage and eliminated the polio virus from New Zealand.