Retrospective use of whole genome sequencing to better understand an outbreak of Salmonella enterica serovar Mbandaka in New South Wales, Australia

Introduction@#Salmonella enterica serovar Mbandaka is an infrequent cause of salmonellosis in New South Wales (NSW) with an average of 17 cases reported annually. This study examined the added value of whole genome sequencing (WGS) for investigating a non-point source outbreak of Salmonella ser. Mbandaka with limited geographical spread.@*Methods@#In February 2016, an increase in Salmonella ser. Mbandaka was noted in New South Wales, and an investigation was initiated. A WGS study was conducted three months after the initial investigation, analysing the outbreak Salmonella ser. Mbandaka isolates along with 17 human and non-human reference strains from 2010 to 2015.@*Results@#WGS analysis distinguished the original outbreak cases (n = 29) into two main clusters: Cluster A (n = 11) and Cluster B (n = 6); there were also 12 sporadic cases. Reanalysis of food consumption histories of cases by WGS cluster provided additional specificity when assessing associations. Discussion: WGS has been widely acknowledged as a promising high-resolution typing tool for enteric pathogens. This study was one of the first to apply WGS to a geographically limited cluster of salmonellosis in Australia. WGS clearly distinguished the outbreak cases into distinct clusters, demonstrating its potential value for use in real time to support non-point source foodborne disease outbreaks of limited geographical spread.

The changing epidemiology of measles in an era of elimination: lessons from health-care-setting transmissions of measles during an outbreak in New South Wales, Australia, 2012

Introduction: In countries where measles is rare, health-care-setting transmissions remain problematic. Australia experienced its largest measles outbreak in 15 years in 2012 with 199 cases reported nationally; 170 cases occurred in the state of New South Wales (NSW) with symptom onset between 7 April and 29 November 2012. Methods: A descriptive study was conducted using measles case data obtained from metropolitan Sydney local health districts in NSW in 2012. Characteristics of measles source and secondary cases were described. Details of health-care presentations resulting and not resulting in measles transmission were also analysed. Results: There were 168 confirmed and two probable cases resulting in 405 documented health-care presentations. Thirty-four secondary cases acquired in health-care settings were identified, including 29 cases resulting from 14 source cases and 5 cases whose source could not be identified. Health-care-acquired cases accounted for 20% of all cases in this outbreak. Source cases were more likely to be of Pacific Islander descent (p = 0.009) and to have had more presentations before diagnosis (p = 0.012) compared to other cases. The percentage of presentations to emergency departments was higher for presentations that resulted in transmission compared to those that did not (71.4% and 37.6%, respectively, p = 0.028). There were no significant differences between transmission and non-transmission presentations with respect to presence of rash and infection control measures (p = 0.762 and p = 0.221, respectively), although the power to detect these differences was limited. Rash was reported at 66% of the presentations. Conclusion: Development of and adherence to protocols for the management of patients presenting to hospitals with fever and rash will minimize secondary transmission of measles.

Effect of antiviral prophylaxis on influenza outbreaks in aged care facilities in three local health districts in New South Wales, Australia, 2014

BACKGROUND: There was a record number (n = 111) of influenza outbreaks in aged care facilities in New South Wales, Australia during 2014. To determine the impact of antiviral prophylaxis recommendations in practice, influenza outbreak data were compared for facilities in which antiviral prophylaxis and treatment were recommended and for those in which antivirals were recommended for treatment only. METHODS: Routinely collected outbreak data were extracted from the Notifiable Conditions Information Management System for two Local Health Districts where antiviral prophylaxis was routinely recommended and one Local Health District where antivirals were recommended for treatment but not routinely for prophylaxis. Data collected on residents included counts of influenza-like illness, confirmed influenza, hospitalizations and related deaths. Dates of onset, notification, influenza confirmation and antiviral recommendations were also collected for analysis. The Mann–Whitney U test was used to assess the significance of differences between group medians for key parameters. RESULTS: A total of 41 outbreaks (12 in the prophylaxis group and 29 in the treatment-only group) were included in the analysis. There was no significant difference in overall outbreak duration; outbreak duration after notification; or attack, hospitalization or case fatality rates between the two groups. The prophylaxis group had significantly higher cases with influenza-like illness (P = 0.03) and cases recommended antiviral treatment per facility (P = 0.01). DISCUSSION: This study found no significant difference in key outbreak parameters between the two groups. However, further high quality evidence is needed to guide the use of antivirals in responding to influenza outbreaks in aged care facilities.