New Zealand's experience of the 1918-19 influenza pandemic: a systematic review after 100 years.

BACKGROUND

The 1918-1919 influenza pandemic has been New Zealand's most severe disaster event (around 9,000 deaths). We aimed to review the literature related to this pandemic in New Zealand and among New Zealanders overseas, to identify any remaining research gaps (given ongoing risks of future influenza pandemics and from new pathogens, eg, synthetic bioweapons).

METHODS

Systematic literature searches and comparisons with international findings for this pandemic to facilitate identification of research gaps.

RESULTS

A total of 61 relevant publications were identified. The epidemiological patterns reported were largely consistent with the international literature for this pandemic. These features included the w-shaped age-distribution for mortality, and the much higher mortality rates for indigenous people (ie, seven-fold for Māori vs New Zealand European). But some novel risk factors were identified (eg, large chest size as a risk factor for death in military personnel), and there was an extremely high mortality troop ship outbreak (probably related to crowding). In contrast to some international work, there was an apparent lack of a socio-economic gradient in mortality rates in two studies using modern analytical methods. New Zealand work has clearly shown how the pandemic spread via the rail network and internal shipping routes and the rarity of successful measures to prevent spread in contrast to some other jurisdictions. It has also found a marked lack of memorials to the pandemic (in contrast to war memorials). Nevertheless, some research gaps remain, including on the apparent marked reduction in birth rates in 1918-1919 and the reasons for no socio-economic gradient despite other New Zealand evidence for occupational class variation in lifespan at this time.

CONCLUSIONS

This is a relatively well-studied disaster event but there remain important research questions relating to this pandemic in New Zealand. Filling these gaps may contribute to improved planning for managing future pandemics.