Epidemiology and direct health care costs of hospitalised legionellosis in New Zealand, 2000–2020

Published:August 26, 2022DOI:


      • Legionellosis is increasingly diagnosed as a cause of hospitalised pneumonia in NZ.
      • Direct health care costs are at least NZ$2·1 million per year.
      • The distribution of cases suggests environmental sources are important.
      • More work is needed to prevent this disease.
      • Surveillance could be improved through routine integration of notification and hospital data.



      Legionellosis is a collective term used for disease caused by Legionella species which result in community and hospital acquired pneumonia worldwide. The aim of this analysis was to describe the epidemiology of legionellosis hospitalisations in Aotearoa New Zealand (NZ) over a 21-year period and quantify the health care costs.


      This study combined national legionellosis notification and hospital discharge data that were linked via the National Health Index (NHI) to provide a more complete dataset of hospitalised cases. The direct cost of hospital care was estimated by multiplying the diagnosis-related group cost-weight by the national price and inflating to 2020/2021 values.


      There were 1479 records matched across notifications and discharge databases, including 990 with principal and 489 with additional diagnosis of legionellosis. Incidence rose to an average of 143 cases per annum for 2016–2020, a rate of 3·2/100,000. The median LOS was 6 days (IQR 4–13·5) with direct costs of $2·1 million per annum over that period. Rates were highest in those aged 65 years and above, male, and of European/Other ethnicity. Hospitalisations showed a peak in spring and summer.


      The rate of hospitalised legionellosis in New Zealand rose from 2000 to 2015, largely reflecting improved diagnosis. This preventable disease results in substantial health care costs. Greater efforts are needed to identify and control sources of exposure. Surveillance could be improved by routine integration of notification and hospital discharge data.


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