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The pertussis epidemic experienced in NSW in 2008–2009 was likely to be in part due to changes in diagnostic practice since 2007, which amplified disease notifications. We used population-based seroepidemiology as a less biased means of interpreting age-specific pertussis infection patterns in NSW from three serosurveys undertaken in 1997–98 (during an epidemic), 2002 (post-epidemic) and 2007 (inter-epidemic), using a standardised pertussis toxin IgG enzyme-linked immunosorbent assay (ELISA). There was a decrease in the proportion of high anti-pertussis toxin IgG titres (>62.5 ELISA Units/mL) across all age groups in the 2007 serosurvey compared to the previous two serosurveys. In the 2007 serosurvey, the proportion of undetectable (

Phage typing has been the traditional strain typing (or .fingerprinting.) method used in Australia for surveillance of common salmonella serovars (such as Salmonella Typhimurium) and outbreak investigations. The need for more accessible, discriminatory and objective methods has been recognised but, until now, none has been widely accepted. Recently, the molecular typing method, known as MLVA (multilocus variable number tandem repeat analysis), has been applied to several Salmonella serovars and promises to provide faster strain typing and cluster identification than phage typing, with comparable or better sensitivity. The present article is intended as a short primer on MLVA typing, which has recently been introduced into routine use at the New South Wales Enteric Reference Laboratory at the Centre for Infectious Diseases and Microbiology, Institute of Clinical Pathology and Medical Research, Westmead.

Molecular strain typing of Mycobacterium tuberculosis has been possible for only about 20 years; it has significantly improved our understanding of the evolution and epidemiology of Mycobacterium tuberculosis and tuberculosis disease. Mycobacterial interspersed repetitive unit typing, based on 24 variable number tandem repeat unit loci, is highly discriminatory, relatively easy to perform and interpret and is currently the most widely used molecular typing system for tuberculosis surveillance. Nevertheless, clusters identified by mycobacterial interspersed repetitive unit typing sometimes cannot be confirmed or adequately defined by contact tracing and additional methods are needed. Recently, whole genome sequencing has been used to identify single nucleotide polymorphisms and other mutations, between genotypically indistinguishable isolates from the same cluster, to more accurately trace transmission pathways. Rapidly increasing speed and quality and reduced costs will soon make large scale whole genome sequencing feasible, combined with the use of sophisticated bioinformatics tools, for epidemiological surveillance of tuberculosis.

The Gram-negative bacterium Yersina pestis is the causative agent of the infectious disease classically referred to as the plague. Wild rodents, especially ground squirrels and prairie dogs, are the natural reservoir of the organism. The organism can occasionally be transmitted to people who are bitten by an infected animal or infected fleas that feed on those animals. Currently, Y. pestis-infected rodents are present on every continent except Australia and Antarctica. Plague is endemic in animals inmany countries in Africa, the Americas and Asia and sporadic infections occur, at varying rates, in humans. In 2003, nine countries reported 2118 cases and 182 deaths from plague: 99% of those cases and deaths were reported from Africa.

Objective: To review enteric disease outbreaks reported to the NSW Department of Health. Methods: Data from existing electronic enteric disease outbreak summary databases were used to describe the number and type of outbreaks reported, burden of illness and cause of the outbreaks. Results: Between 2000 and 2005, 998 enteric disease outbreaks were reported (148 foodborne and 850 non-foodborne), affecting 24260 people and associated with 771 hospitalisations and 21 deaths. Salmonella was confirmed in 28 per cent of foodborne outbreaks, and norovirus in 18 per cent of non-foodborne outbreaks. Conclusions: Enteric disease outbreaks cause a substantial burden of disease in NSW. Michelle CretikosA,C, Barbara TelferB and Jeremy McAnultyB ANSW Public Health Officer Training Program, NSW Department of Health BCommunicable Diseases Branch, NSW Department of Health CCorresponding author: Email: mcret@doh.health.nsw.gov.au. breaks of gastroenteritis occur in institutions, such as schools, childcare centres and residential care facilities. Institutional outbreaks of gastroenteritis are usually caused by highly infectious viruses such as norovirus and rotavirus, and spread predominantly through person-toperson contact.1,5 Under the Public Health Act (NSW) 1991, 12 enteric conditions are currently notifiable in NSW and must be reported to NSW Health by doctors, laboratories and hospitals, including: botulism, cholera, cryptosporidiosis, giardiasis, haemolytic uraemic syndrome (HUS), shigatoxigenic Escherichia coli (STEC) infection, hepatitis A, hepatitis E, listeriosis, salmonellosis, shigellosis and typhoid. Some of these diseases are primarily foodborne in origin, such as salmonellosis, typhoid and listeriosis. In addition to individual disease notifications, outbreaks of suspected foodborne disease in two or more people related in time or place, and outbreaks of gastroenteritis among people of any age in an institution (eg an educational, residential, childcare or healthcare institution) are also notifiable by doctors and institutions. Where public health units identify clusters of disease or outbreaks, they will launch an outbreak investigation. Summary reports of enteric disease outbreaks are provided by public health units and entered into the relevant enteric disease outbreak databases held at the NSW Department of Health. We analysed enteric disease outbreaks reported to the NSW Department of Health for the five-year period July 2000–June 2005. This analysis aimed to describe the number, epidemiology and cause of the enteric disease outbreaks reported during this period. Methods The two existing NSW Health enteric disease outbreak databases – the OzFoodNet Outbreak Summary Database and the Gastroenteritis in Institutions Database – were used. For the purposes of the present study, the data contained within the two enteric disease outbreak summary databases was separated into two categories: • foodborne and suspected foodborne outbreaks, and • non-foodborne outbreaks of enteric disease. If the setting of the outbreak was an institution (ie aged care facility, hospital, child care centre, school, correctional facility or other institutional setting) and the method of transmission was unknown, the outbreak was assumed

Salmonellosis caused by enteropathogens of the genus Salmonella is a major public health concern in Australia. Serotyping is usually performed in enteric reference laboratories for the initial characterisation and differentiation of Salmonella species. Further strain identification within serovars may be achieved by phage typing and this is used as an epidemiological tool for outbreak investigations. Phage typing has limited discriminatory ability and the necessity of sending specimens interstate from NSW for this test causes delays in recognising outbreaks and reduces the likelihood of identifying the source. Multilocus variable-number tandem-repeat analysis has a high discriminatory power and faster turnaround time, and is the method of choice for outbreak investigation. Additionally, a newly developed multiplex PCR-based reverse line blot hybridisation system is able to identify most of the phage types prevalent in NSW. Combining these last two molecular methods will significantly enhance outbreak investigations and surveillance of Salmonella infections in NSW.

Several molecular typing methods are available to assist public health practitioners in identifying clusters of recently acquired tuberculosis cases. Molecular typing or fingerprinting investigates variations in microbial populations, defines specific clones and identifies outbreaks by matching molecular fingerprints of epidemiologically linked isolates. The combination of two or more methods, with different preselected genomic loci in the Mycobacterium tuberculosis genome, have been used to identify and track outbreaks, define high-risk groups and target prevention strategies.Table 1 compares three current typing methods.