Health impacts of war: case studies of New Zealand veterans of the First World War.

AIM: Armed conflict remains a tragic feature of the modern world and so it is necessary to continue to study its health impacts. Even the study of historical conflicts is relevant given that certain health impacts are common to most wars e.g., post-traumatic stress disorder (PTSD). METHODS: This study built on a previous quantitative analysis of a randomly selected group of 200 New Zealand veterans from the First World War (WWI). From this sample we selected 10 cases that illustrated particular themes around morbidity impacts. RESULTS: The theme of severity of impacts was illustrated with a case who was severely wounded and died from suicide when back in New Zealand, and another case with severe PTSD. The theme of the high frequency of non-fatal conditions was revealed with cases illustrating new diagnoses (a case with n=8 diagnoses), hospitalisations for new conditions (n=6), non-fatal injury events (n=3) and for sexually transmitted infections (n=3). The theme of chronic debility as a consequence of various conditions was illustrated with cases who had suffered from being gassed or having gastroenteritis, malaria or pandemic influenza. CONCLUSION: These 10 selected cases reiterate how severe and extensive the morbidity burden for military personnel in WWI could be. Also illustrated is how the morbidity could contribute to adverse impacts on some of their lives after returning to New Zealand.

The unseen casualties of the First World War: insights from a randomly selected military sample.

AIMS: Studies of the morbidity burden of military personnel participating in the First World War (WWI) have tended to focus on specific outcomes (e.g., injuries). Therefore, we aimed for a more complete assessment. METHODS: From a random sample of active war service-exposed New Zealand WWI veterans used in previously published work, we examined a random subsample of 200 personnel. Data on diagnoses, hospitalisations and outcomes were extracted from the online archival military files. RESULTS: These personnel experienced a very high morbidity burden with 94% having at least one new condition diagnosed during their military service (mean: 2.4 per individual; range: 0 to 8). The relative severity of these conditions was reflected by the high level of hospitalisation (89% at least once; mean: 1.8 hospitalisations for new conditions per individual) and 59% of personnel being deemed no longer fit for military service at some stage. More of the new diagnoses were for infectious diseases than for conflict-related injuries (117 vs 50 cases per 100 personnel). Respiratory conditions such as influenza, pneumonia and tuberculosis affected 33% of personnel, and 14% were diagnosed with sexually transmitted infections. Diseases reflecting hazardous environmental conditions were relatively common e.g., for dysentery/gastroenteritis in 12% and scabies in 5% of personnel. Diagnoses suggestive of post-traumatic stress disorder (PTSD) were present in 10% and chemical warfare injuries in 6%. CONCLUSIONS: The overall morbidity burden of this military force in WWI was very high, and much higher than the previous official estimates.

Tobacco endgame intervention impacts on health gains and Maori:non-Maori health inequity: a simulation study of the Aotearoa/New Zealand Tobacco Action Plan.

BACKGROUND: The Aotearoa/New Zealand Government is aiming to end the tobacco epidemic and markedly reduce Maori:non-Maori health inequalities by legislating: (1) denicotinisation of retail tobacco, (2) 95% reduction in retail outlets and (c) a tobacco free-generation whereby people born after 2005 are unable to legally purchase tobacco. This paper estimates future smoking prevalence, mortality inequality and health-adjusted life year (HALY) impacts of these strategies. METHODS: We used a Markov model to estimate future yearly smoking and vaping prevalence, linked to a proportional multistate life table model to estimate future mortality and HALYs. RESULTS: The combined package of strategies (plus media promotion) reduced adult smoking prevalence from 31.8% in 2022 to 7.3% in 2025 for Maori, and 11.8% to 2.7% for non-Maori. The 5% smoking prevalence target was forecast to be achieved in 2026 and 2027 for Maori males and females, respectively.The HALY gains for the combined package over the population's remaining lifespan were estimated to be 594 000 (95% uncertainty interval (UI): 443 000 to 738 000; 3% discount rate). Denicotinisation alone achieved 97% of these HALYs, the retail strategy 19% and tobacco-free generation 12%.By 2040, the combined package was forcat to reduce the gap in Maori:non-Maori all-cause mortality rates for people 45+ years old by 22.9% (95% UI: 19.9% to 26.2%) for females and 9.6% (8.4% to 11.0%) for males. CONCLUSION: A tobacco endgame strategy, especially denicotinisation, could deliver large health benefits and dramatically reduce health inequities between Maori and non-Maori in Aotearoa/New Zealand.

Disease-Related Loss to Government Funding: Longitudinal Analysis of Individual-Level Health and Tax Data for an Entire Country.

OBJECTIVES: The objective of this longitudinal analysis was to estimate funding loss in terms of tax revenue to the New Zealand (NZ) government from disease and injury among working age adults. METHODS: Linked national health and tax data sets of the usually resident population between 2006 and 2016 were used to model 40 disease states simultaneously in a fixed-effects regression analysis to estimate population-level tax loss from disease and injury. To estimate tax revenue loss to the NZ government, we modeled a counterfactual scenario where all disease/injury was cause deleted. RESULTS: The estimated tax paid by all 25- to 64-year-olds in the eligible NZ population was $15 773 million (m) per annum (US dollar 2021), or $16 446 m for a counterfactual as though no one had any disease disease-related income loss (a 4.3% or $672.9 m increase in tax revenue per annum). The disease that-if it had no impact on income-generated the greatest impact was mental illness, contributing 34.7% ($233.3 m) of all disease-related tax loss, followed by cardiovascular (14.7%, $99.0 m) and endocrine (10.2%, $68.8 m). Tax revenue gains after deleting all disease/injury increased up to 65 years of age, with the largest contributor occurring among 60- to 64-year-olds ($131.7 m). Varied results were also observed among different ethnicities and differing levels of deprivation. CONCLUSIONS: This study finds considerable variation by disease on worker productivity and therefore tax revenue in this high-income country. These findings strengthen the economic and government case for prevention, particularly the prevention of mental health conditions and cardiovascular disease.

Updated Health and Cost Impacts of Electronic Nicotine Delivery Systems, Using Recent Estimates of Relative Harm for Vaping Compared to Smoking.

BACKGROUND: Measuring population health and costs effects of liberalizing access to electronic nicotine delivery systems (ENDS) is an evolving field with high persisting uncertainty. A critical area of uncertainty for policy-makers are estimates of net harms from ENDS relative to cigarettes, therefore, we model these harms using updated estimates incorporating disease specificity. METHODS: We use updated estimates of relative harm of vaping vs smoking, based upon relevant biomarker studies to model the impact of liberalizing access to ENDS in New Zealand (NZ), relative to a ban (where ENDS are not legally available), in an existing proportional multi-state life-table model of 16 tobacco-related diseases. RESULTS: This modeling suggests that ENDS liberalization results in an expected gain of 195 000 quality-adjusted life-years (QALYs) over the remainder of the NZ population's lifespan. There was wide uncertainty in QALYs gained (95% uncertainty interval [UI] = -8000 to 406 000) with a 3.2% probability of net health loss (based upon the number of simulation runs returning positive QALY gains). The average per capita health gain was 0.044 QALYs (equivalent to an extra 16 days of healthy life). Health system cost-savings were expected to be NZ$2.8 billion (US$2.1 billion in 2020 US$; 95%UI: -0.3 to 6.2 billion [2011 NZ$]), with an estimated 3% chance of a net increase in per capita cost. CONCLUSIONS: This updated modeling around liberalizing ENDs in NZ, still suggests likely net health and cost-saving benefits-but of lesser magnitude than previous work and with a small possibility of net harm to population health. IMPLICATIONS: This study found evidence using updated biomarker studies that ENDS liberalization could result in QALY gains across the New Zealand population lifespan that are also cost-saving to the health system. Governments should include the information from these types of modeling studies in their decision-making around potentially improving access to ENDS for existing smokers, while at the same further reducing access to tobacco.

Improving on estimates of the potential relative harm to health from using modern ENDS (vaping) compared to tobacco smoking.

BACKGROUND: Although the harm to health from electronic nicotine delivery systems (ENDS) compared to smoked tobacco remains highly uncertain, society and governments still need to know the likely range of the relative harm to inform regulatory policies for ENDS and smoking. METHODS: We identified biomarkers with specificity of association with different disease groupings e.g., volatile organic compound (VOCs) for chronic obstructive pulmonary disease; and tobacco-specific N´-nitrosamines (TSNAs) and polycyclic aromatic hydrocarbons (PAHs) for all cancers. We conducted a review of recent studies (post January 2017) that compared these biomarkers between people exclusively using ENDS and those exclusively smoking tobacco. The percentage differences in these biomarkers, weighted by study size and adjusted for acrolein from other sources, were used as a proxy for the assumed percentage difference in disease harm between ENDS and smoking. These relative differences were applied to previously modelled estimates of smoking-related health loss (in health-adjusted life-years; HALYs). RESULTS: The respective relative biomarker levels (ENDS vs smoking) were: 28% for respiratory diseases (five results, three studies); 42% for cancers (five results, four studies); and 35% for cardiovascular (seven results, four studies). When integrated with the HALY impacts by disease, the overall harm to health from ENDS was estimated to be 33% that of smoking. CONCLUSIONS: This analysis, suggests that the use of modern ENDS devices (vaping) could be a third as harmful to health as smoking in a high-income country setting. But this estimate is based on a limited number of biomarker studies and is best be considered a likely upper level of ENDS risk given potential biases in our method (i.e., the biomarkers used being correlated with more unaccounted for toxicants in smoking compared to with using ENDS).

Failures of quarantine systems for preventing COVID-19 outbreaks in Australia and New Zealand.

OBJECTIVES: To identify COVID-19 quarantine system failures in Australia and New Zealand. DESIGN, SETTING, PARTICIPANTS: Observational epidemiological study of travellers in managed quarantine in Australia and New Zealand, to 15 June 2021. MAIN OUTCOME MEASURES: Number of quarantine system failures, and failure with respect to numbers of travellers and SARS-CoV-2-positive travellers. RESULTS: We identified 22 quarantine system failures in Australia and ten in New Zealand to 15 June 2021. One failure initiated a COVID-19 outbreak that caused more than 800 deaths (the Victorian "second wave"); nine lockdowns were linked with quarantine system failures. The failure risk was estimated to be 5.0 failures per 100 000 travellers passing through quarantine and 6.1 (95% CI, 4.0-8.3) failures per 1000 SARS-CoV-2-positive travellers. The risk per 1000 SARS-CoV-2-positive travellers was higher in New Zealand than Australia (relative risk, 2.0; 95% CI, 1.0-4.2). CONCLUSIONS: Quarantine system failures can be costly in terms of lives and economic impact, including lockdowns. Our findings indicate that infection control in quarantine systems in Australia and New Zealand should be improved, including vaccination of quarantine workers and incoming travellers, or that alternatives to hotel-based quarantine should be developed.

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 Maori 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.

SecurAcath for Securing Peripherally Inserted Central Catheters: A NICE Medical Technology Guidance.

Central venous catheters are commonly used to deliver therapies and to monitor patients, and require securing at the point of percutaneous entry to avoid dislodgement. SecurAcath is a catheter securement device designed for central venous catheters. The National Institute for Health and Care Excellence, as a part of its Medical Technologies Evaluation Programme, selected this device for evaluation and invited the manufacturer, Interrad Medical, to submit clinical and economic evidence. The King's Technology Evaluation Centre, an External Assessment Centre commissioned by the National Institute for Health and Care Excellence, independently critiqued the manufacturer's submissions. The External Assessment Centre found a lack of evidence comparing SecurAcath with alternative approaches to securement (StatLock, suturing, tape securement), with one unpublished randomised controlled trial providing the strongest evidence. The External Assessment Centre conducted a new systematic review and meta-analysis and concluded that there is some evidence indicating the non-inferiority of SecurAcath compared to StatLock. The External Assessment Centre considered the manufacturer's economic model to be appropriate but made revisions to some parameters and noted significant heterogeneity in the included studies. The revised model indicated that StatLock was more cost effective than SecurAcath for catheter indwell times of up to 5 days; however, for medium- and long-term indwell times, SecurAcath was the most cost-effective option. The National Institute for Health and Care Excellence Medical Technologies Guidance MTG 34, issued in June 2017, recommended the adoption of SecurAcath for securing peripherally inserted central catheters within the National Health Service in England.

Virtual Touch™ Quantification to Diagnose and Monitor Liver Fibrosis in Hepatitis B and Hepatitis C: A NICE Medical Technology Guidance.

Virtual Touch™ Quantification (VTq) is a software application used with Siemens Acuson ultrasound scanners to assess the stiffness of liver tissue. The National Institute for Health and Care Excellence (NICE) Medical Technologies Advisory Committee (MTAC) selected VTq for evaluation and invited the company to submit clinical and economic evidence. King's Technology Evaluation Centre, an External Assessment Centre (EAC) commissioned by NICE, independently assessed the evidence submitted. The EAC conducted its own systematic review, meta-analysis and economic analysis to supplement the company's submitted evidence. The meta-analyses comparing VTq and transient elastography (TE) with liver biopsy (LB) provided pooled estimates of liver stiffness and stage of fibrosis for the study populations (hepatitis B, hepatitis C or combined populations). When comparing significant fibrosis (Metavir score F ≥ 2) for both hepatitis B and C, VTq had slightly higher values for both sensitivity and specificity (77 and 81 %) than TE (76 and 71 %). The overall prevalence of cirrhosis (F4, combined populations) was similar with VTq and TE (23 vs. 23 %), and significant fibrosis (F ≥ 2) was lower for VTq than for TE (55 vs. 62 %). The EAC revised the company's de novo cost model, which resulted in a cost saving of £53 (against TE) and £434 (against LB). Following public consultation, taking into account submitted comments, NICE Medical Technology Guidance MTG27 was published in September 2015. This recommended the adoption of the VTq software to diagnose and monitor liver fibrosis in patients with hepatitis B or hepatitis C.

Multicentre prospective survey of SeHCAT provision and practice in the UK.

OBJECTIVE: A clinical diagnosis of bile acid malabsorption (BAM) can be confirmed using SeHCAT (tauroselcholic ((75)selenium) acid), a radiolabelled synthetic bile acid. However, while BAM can be the cause of chronic diarrhoea, it is often overlooked as a potential diagnosis. Therefore, we investigated the use of SeHCAT for diagnosis of BAM in UK hospitals. DESIGN: A multicentre survey was conducted capturing centre and patient-level information detailing patient care-pathways, clinical history, SeHCAT results, treatment with bile acid sequestrants (BAS), and follow-up in clinics. Eligible data from 38 centres and 1036 patients were entered into a validated management system. RESULTS: SeHCAT protocol varied between centres, with no standardised patient positioning, and differing referral systems. Surveyed patients had a mean age of 50 years and predominantly women (65%). The mean SeHCAT retention score for all patients was 19% (95% CI 17.8% to 20.3%). However, this differed with suspected BAM type: type 1: 9% (95% CI 6.3% to 11.4%), type 2: 21% (95% CI 19.2% to 23.0%) and type 3: 22% (95% CI 19.6% to 24.2%). Centre-defined 'abnormal' and 'borderline' results represented over 50% of the survey population. BAS treatment was prescribed to only 73% of patients with abnormal results. CONCLUSIONS: The study identified a lack of consistent cut-off/threshold values, with differing centre criteria for defining an 'abnormal' SeHCAT result. BAS prescription was not related in a simple way to the SeHCAT result, nor to the centre-defined result, highlighting a lack of clear patient care-pathways. There is a clear need for a future diagnostic accuracy study and a better understanding of optimal management pathways.

A Single-centre Early Phase Randomised Controlled Three-arm Trial of Open, Robotic, and Laparoscopic Radical Cystectomy (CORAL).

BACKGROUND: Laparoscopic radical cystectomy (LRC) and robot-assisted radical cystectomy (RARC) are increasingly popular, but high-level evidence for these techniques remains lacking. OBJECTIVE: To compare the outcomes of patients undergoing open radical cystectomy (ORC), RARC, and LRC. DESIGN, SETTING, AND PARTICIPANTS: From March 2009 to July 2012, 164 patients requiring radical cystectomy for muscle-invasive bladder cancer or high-risk non-muscle-invasive bladder cancer were invited to participate, with an aim of recruiting 47 patients into each arm. Overall, 93 were suitable for trial inclusion; 60 (65%) agreed and 33 (35%) declined. INTERVENTION: ORC, RARC, or LRC with extracorporeal urinary diversion. OUTCOME MEASUREMENTS AND STATISTICAL ANALYSIS: Primary end points were 30- and 90-d complication rates. Secondary end points were perioperative clinical, pathologic, and oncologic outcomes, and quality of life (QoL). The Fisher exact test and analysis of variance were used for statistical analyses. RESULTS AND LIMITATIONS: The 30-d complication rates (classified by the Clavien-Dindo system) varied significantly between the three arms (ORC: 70%; RARC: 55%; LRC: 26%; p=0.024). ORC complication rates were significantly higher than LRC (p<0.01). The 90-d complication rates did not differ significantly between the three arms (ORC: 70%; RARC: 55%; LRC 32%; p=0.068). Mean operative time was significantly longer in RARC compared with ORC or LRC. ORC resulted in a slower return to oral solids than RARC or LRC. There were no significant differences in QoL measures. Major limitations are the small sample size and potential surgeon bias. CONCLUSIONS: The 30-d complication rates varied by type of surgery and were significantly higher in the ORC arm than the LRC arm. There was no significant difference in 90-d Clavien-graded complication rates between the three arms. PATIENT SUMMARY: We compared patients having open, robotic, or laparoscopic bladder removal surgery for bladder cancer and found no difference in Clavien-graded complication rates at 90 d.

The geko™ electro-stimulation device for venous thromboembolism prophylaxis: a NICE medical technology guidance.

The geko™ device is a single-use, battery-powered, neuromuscular electrostimulation device that aims to reduce the risk of venous thromboembolism (VTE). The National Institute for Health and Care Excellence (NICE) selected the geko™ device for evaluation, and invited the manufacturer, Firstkind Ltd, to submit clinical and economic evidence. King's Technology Evaluation Centre, an External Assessment Centre (EAC) commissioned by the NICE, independently assessed the evidence submitted. The sponsor submitted evidence related to the geko™ device and, in addition, included studies of other related devices as further clinical evidence to support a link between increased blood flow and VTE prophylaxis. The EAC assessed this evidence, conducted its own systematic review and concluded that there is currently limited direct evidence that geko™ prevents VTE. The sponsor's cost model is based on the assumption that patients with an underlying VTE risk and subsequently treated with geko™ will experience a reduction in their baseline risk. The EAC assessed this cost model but questioned the validity of some model assumptions. Using the EACs revised cost model, the cost savings for geko™ prophylaxis against a 'no prophylaxis' strategy were estimated as £197 per patient. Following a second public consultation, taking into account a change in the original draft recommendations, the NICE medical technologies guidance MTG19 was issued in June 2014. This recommended the adoption of the geko™ for use in people with a high risk of VTE and when other mechanical/pharmacological methods of prophylaxis are impractical or contraindicated in selected patients within the National Health Service in England.

Mortality of first world war military personnel: comparison of two military cohorts.

OBJECTIVE: To identify the impact of the first world war on the lifespan of participating military personnel (including in veterans who survived the war). DESIGN: Comparison of two cohorts of military personnel, followed to death. SETTING: Military personnel leaving New Zealand to participate in the first world war. PARTICIPANTS: From a dataset of the New Zealand Expeditionary Forces, we randomly selected participants who embarked on troopships in 1914 and a comparison non-combat cohort who departed on troopships in late 1918 (350 in each group). MAIN OUTCOME MEASURES: Lifespan based on dates of birth and death from a range of sources (such as individual military files and an official database of birth and death records). RESULTS: A quarter of the 1914 cohort died during the war, with deaths from injury predominating (94%) over deaths from disease (6%). This cohort had a significantly shorter lifespan than the late 1918 "non-combat" cohort, with median ages of death being 65.9 versus 74.2, respectively (a difference of 8.3 years shown also in Kaplan-Meier survival curves, log rank P<0.001). The difference for the lifespan of veterans in the postwar period was more modest, with median ages of death being 72.6 versus 74.3, respectively (a difference of 1.7 years, log rank P=0.043). There was no evidence for differences between the cohorts in terms of occupational class, based on occupation at enlistment. CONCLUSIONS: Military personnel going to the first world war in 1914 from New Zealand lost around eight years of life (relative to a comparable military cohort). In the postwar period they continued to have an increased risk of premature death.

Risk factors for death from pandemic influenza in 1918-1919: a case-control study.

BACKGROUND: Despite the persisting threat from future influenza pandemics, much is still unknown about the risk factors for death from such events, and especially for the 1918-1919 influenza pandemic. METHODS: A case-control study was performed to explore possible risk factors for death from pandemic influenza among New Zealand military personnel in the Northern Hemisphere in 1918-1919 (n = 218 cases, n = 221 controls). Data were compiled from a Roll-of-Honour dataset, a dataset of nearly all military personnel involved in the war and archived individual records. RESULTS: In the fully adjusted multivariable model, the following were significantly associated with increased risk of death from pandemic influenza: age (25-29 years), pre-pandemic hospitalisations for a chronic condition (e.g. tuberculosis), relatively early year of military deployment, a relatively short time from enlistment to foreign service, and having a larger chest size (e.g. adjusted odds ratio for 90-99 cm versus <90 cm was 2·45; 95% CI=1·47-4·10). There were no significant associations in the fully adjusted model with military rank, occupational class at enlistment, and rurality at enlistment. CONCLUSIONS: This is one of the first published case-control studies of mortality risk factors for the 1918-1919 influenza pandemic. Some of the findings are consistent with previous research on risk factors (such as chronic conditions and age groups), but others appear more novel (e.g., larger chest size). As all such historical analyses have limitations, there is a need for additional studies in other settings as archival World War One records become digitalised.

Fatal injury epidemiology among the New Zealand military forces in the First World War.

BACKGROUND: Despite the large mortality burden of First World War (WW1) on New Zealand (NZ) military forces, no analysis using modern epidemiological methods has ever been conducted. We therefore aimed to study injury-related mortality amongst NZ military forces in WW1. METHODS: An electronic version of the Roll-of-Honour for NZ Expeditionary Force (NZEF) personnel was supplemented with further coding and analysed statistically. We also performed literature searches to provide context. RESULTS: Out of a total of 16,703 deaths occurring during the war (28 July 1914 to 11 November 1918), injury deaths predominated: 65.1% were "killed in action" (KIA), 23.4% "died of wounds" (DOW), 1.0% were other injuries (e.g. "accidents", drownings, suicides and executions), and 10.5% were other causes (mainly disease). During the course of the war, the annual mortality rate from injury (for KIA + DOW) per 10,000 NZEF personnel in the North Hemisphere peaked at 1335 in 1915 (Gallipoli campaign) and then peaked again in 1917 at 937 (largely the Battle of Passchendaele). Some of the offensive campaigns involved very high mortality peaks (e.g. 2 days with over 450 deaths per day in October 1917). CONCLUSIONS: Participation in First World War was by far the worst fatal injury event in New Zealand's history. Many of these injury deaths could be considered to have been preventable through: better diplomacy (to prevent the war), improved military planning to reduce failed campaigns (e.g. Gallipoli, Passchendaele), earlier use of protective equipment such as helmets, and improved healthcare services.

Severe impact of the 1918-19 pandemic influenza in a national military force.

The impact of pandemic influenza on the New Zealand Expeditionary Force (NZEF) in 1918-19 has never been studied using modern epidemiological methods. Therefore we analysed mortality and descriptive data from various sources for these military personnel. An estimated 930 NZEF personnel deaths from pandemic influenza occurred in 1918-19, making it the main cause of disease deaths, and representing 5.1% of all NZEF deaths from World War One (WW1). The epidemic curve was much more drawn out in the Northern Hemisphere compared with the Southern Hemisphere. Mortality rates varied markedly by setting (e.g. in military camps, by country and by hemisphere). Significantly higher mortality rates were found amongst NZEF personnel: aged 30-34 years, those of Maori ethnicity, those with a rural background, and those who left New Zealand for Europe in 1918. In conclusion, this work documents the heavy mortality burden from pandemic influenza amongst this national military force and highlights the large variations in mortality rates through host and environmental factors.