Elsevier

Journal of Infection

Volume 70, Issue 2, February 2015, Pages 127-134
Journal of Infection

Increasing incidence of invasive group A streptococcus disease in New Zealand, 2002–2012: A national population-based study

https://doi.org/10.1016/j.jinf.2014.09.001Get rights and content

Highlights

  • We found an apparent increase in the incidence of invasive GAS disease in New Zealand.

  • There was significant sociodemographic variation in the incidence of disease.

  • Overall, 59% of GAS isolates were theoretically covered by an M-protein vaccine.

Summary

Objectives

To analyse the incidence, demographics and molecular epidemiology of invasive group A streptococcal (GAS) disease in New Zealand between 2002 and 2012.

Methods

Using laboratory-based surveillance data, invasive GAS isolates were identified from the Institute of Environmental Science and Research, New Zealand. Hospitalization and mortality data were obtained from the New Zealand Ministry of Health. Molecular typing was performed by sequence analysis of the emm gene.

Results

The incidence of invasive GAS infections increased from 3.9 per 100,000 population in 2002 to 7.9 per 100,000 population (P < 0.001) in 2012. The incidence was highest in the over 75-year age group, and in Pacific peoples. There was temporal variation in emm types associated with invasive GAS disease, with emm1 being the overall predominant emm type. The diversity of emm types varied significantly according to ethnicity. Overall, 59% of GAS isolates were theoretically covered by an experimental M-protein vaccine.

Conclusions

Our study provides valuable data on the epidemiology of invasive GAS disease in New Zealand, and represents one of the few studies to assess such longitudinal data across an entire nation. The increase in invasive GAS disease is concerning, and reasons for this should be explored further.

Introduction

Group A streptococcus (GAS) is a major human pathogen, and infections with GAS are associated with considerable global morbidity and mortality.1, 2 Acute clinical manifestations of GAS disease range from pharyngitis and superficial skin infections through to severe invasive syndromes such as necrotizing fasciitis, puerperal sepsis, bacteraemia and streptococcal toxic shock syndrome.2, 3 Moreover, the non-suppurative immunological sequelae of GAS infection (rheumatic fever, rheumatic heart disease and post-streptococcal glomerulonephritis) result in a significant clinical and economic disease burden.4, 5

The incidence of invasive GAS disease varies both temporally and geographically.6, 7, 8, 9, 10 In most developed countries, the reported incidence of invasive GAS disease is between 2 and 4 cases per 100,000 population.3 However, a previous study in Auckland, New Zealand suggested that the incidence of invasive GAS disease (8.1 per 100,000 population) was considerably higher in New Zealand compared to similar developed countries.11 In addition, these authors described notable disparity in incidence rates, with the highest incidence in Māori (indigenous New Zealander) and Pacific peoples.11

Contemporary molecular typing of GAS is carried out by sequence analysis of the hypervariable region of the emm gene.12 This gene encodes the M-protein, a major virulence factor of GAS, involved in adhesion to host tissues and immune evasion.13 To date, the most clinically advanced GAS vaccine candidates are those that target the N-terminal region of the M-protein. A 26-valent M-protein demonstrated good safety and immunogenicity in Phase I and II clinical trials,14 and subsequently, a 30-valent vaccine has recently been developed to increase serotype coverage.15, 16 However, a prerequisite for success of these M-protein based vaccines is adequate coverage of locally circulating GAS emm types.

To date, longitudinal changes in the relative proportions of circulating emm types associated with invasive GAS disease have only rarely been described.17 In addition, no studies have systematically assessed temporal trends in the epidemiology of invasive GAS disease in New Zealand. Accordingly, we sought to: (i) describe the incidence, trends and demographics of invasive GAS disease in New Zealand over an 11-year period and (ii) to describe the molecular epidemiology of circulating GAS emm types associated with invasive GAS disease.

Section snippets

Setting, patients and isolates

New Zealand is an island nation in the South West Pacific, with a resident population of approximately 4.4 million. The country is ethnically diverse, consisting of the following main ethnicities: 67% European, 15% Māori, 10% Asian, 7% Pacific peoples and 1% of other ethnicities.

Unlike acute rheumatic fever, invasive GAS disease is not a notifiable condition in New Zealand. Consequently, surveillance of invasive GAS infection is predominantly passive and laboratory-based, depending on

Number, incidence and outcomes of invasive GAS infections

Applying our case definition, a total of 2861 invasive GAS infections were identified over the study period. Of these, 2755 infections (96%) were based on isolation from a sterile site: 2535 (92%) from blood, 159 (6%) bone and joint, 26 (1%) from pleura, 19 (0.5%) from cerebrospinal fluid, 15 (0.5%) from peritoneal fluid, and one isolate from pericardial fluid. Of the remaining 105 cases in which a GAS isolate had no anatomical site specified, 75 had an ICD-10 hospital discharge code of M725

Discussion

In this study, we analysed the trends and demographics of invasive GAS disease in the New Zealand population between 2002 and 2012. The incidence of invasive GAS infections approximately doubled over the study period from 3.9 per 100,000 population in 2002 to 7.9 per 100,000 population (P < 0.001) in 2012. In addition, we observed notable sociodemographic variation in the incidence of invasive GAS disease, with the highest rates in Pacific peoples and Māori populations, and in those patients

Funding

This study was supported by funding from the New Zealand Ministry of Health.

Acknowledgements

We thank all diagnostic microbiology laboratories throughout New Zealand for sending GAS isolates to ESR, and physicians involved in the care of these patients.

References (33)

  • A.P. Ralph et al.

    Group A streptococcal diseases and their global burden

    Curr Top Microbiol Immunol

    (2013)
  • A.C. Steer et al.

    Invasive group A streptococcal disease: epidemiology, pathogenesis and management

    Drugs

    (2012)
  • R.J. Milne et al.

    Mortality and hospitalisation costs of rheumatic fever and rheumatic heart disease in New Zealand

    J Paediatr Child Health

    (2012)
  • W. Wong et al.

    Prospective population-based study on the burden of disease from post-streptococcal glomerulonephritis of hospitalised children in New Zealand: epidemiology, clinical features and complications

    J Paediatr Child Health

    (2013)
  • C. Stockmann et al.

    Evolving epidemiologic characteristics of invasive group a streptococcal disease in Utah, 2002–2010

    Clin Infect Dis

    (2012)
  • R.E. O'Loughlin et al.

    Active Bacterial Core Surveillance Team: The epidemiology of invasive group A streptococcal infection and potential vaccine implications: United States, 2000–2004

    Clin Infect Dis

    (2007)
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