Rise in invasive serogroup W meningococcal disease in Australia 2013-2015.

Since 2013, there has been an increase in the number of notified cases of invasive meningococcal disease (IMD) due to serogroup W (MenW) in Australia. In response to this observed increase, the Communicable Diseases Network Australia convened a working group in 2015 to collate and analyse the epidemiology of MenW disease nationally. Enhanced surveillance data collected by jurisdictions were collated and analysed, and whole genome sequencing (WGS) of MenW isolates assessed the genomic relatedness of strains between 2012 and 2015. This report describes that epidemiology. Since 2013, the incidence and proportion of MenW has increased in Australia, rising from an average of 2% of all IMD cases annually (range 0% to 5%) between 1991 and 2012; to 8% (12/149) of cases in 2013, 10% (17/169) in 2014, and 19% (34/182) in 2015. Victoria has been the main affected state, with 50% (17/34) of national cases in 2015. MenW has affected older populations, with a median age between 2003 and 2015 being 44 years. During this period, case fatality was 10.7% (17/159), 2.3 times higher than for all IMD serogroups combined (4.7%, 173/3720). There were 7 deaths due to MenW in 2015 (CFR 21%). WGS has found the majority of Australian isolates cluster within a group of W:P1.5,2:F1-1:ST11 isolates from the United Kingdom and South America, regions where rapid spread and endemic transmission has occurred since 2009. The recent increase in incidence of MenW in Australia is evolving and is being closely monitored. Lessons learned from the international experience will be important in informing the public health response.

Australian vaccine preventable disease epidemiological review series: rubella 2008-2012.

INTRODUCTION: Since the introduction of universal rubella vaccination in 1989, the incidence of rubella and congenital rubella syndrome (CRS) in Australia has declined significantly. Worldwide, there has been a focus on elimination, with the region of the Americas declaring rubella elimination in 2011. This study aims to review Australian rubella epidemiology for the 2008-2012 period, in the context of historical and international trends. METHODS: Notification, hospitalisation and mortality data were sourced from the National Notifiable Diseases Surveillance System, the National Hospital Morbidity Database and the Australian Bureau of Statistics (ABS). Data analysis focused on 2008-2012 for notifications and 2008-2011 for hospitalisations and deaths. ABS population data were used to calculate rates. RESULTS: The average annual rubella notification rate in Australia from 2008-2012 was 0.18 per 100,000 and the average annual hospitalisation rate was 0.03 per 100,000 from 2008-2011. One case of CRS was notified in 2012 and 1 hospitalisation with a principal diagnosis of CRS was recorded in 2008. The median age of rubella notifications was 29 years and 37% of notifications were for infections acquired overseas. DISCUSSION: Rubella continues to be well controlled in Australia and CRS is rare. The low incidence and increasing proportion of imported cases and other evidence suggest that elimination has been achieved; however, for formal verification of rubella elimination the expansion of genotypic surveillance will be required. Ongoing rubella control needs to focus on improved surveillance, maintenance of high levels of vaccine coverage, vaccination of at-risk populations in Australia, and regional and global efforts towards rubella elimination.

Australian vaccine preventable disease epidemiological review series: measles 2000-2011.

BACKGROUND: Since the introduction of measles vaccine to the vaccination schedule, the burden of measles has substantially fallen in Australia. Despite this, a number of recent measles outbreaks have occurred. The aim of this study was to examine the burden of measles in Australia using notification, hospitalisation and mortality data with the objectives of setting a baseline for comparison prior to the introduction of the combined measles-mumps-rubella-varicella vaccine. METHODS: Data were obtained from the Australian National Notifiable Diseases Surveillance System, the National Hospital Morbidity Database and the National Mortality Database to obtain notification, hospitalisation and death data, respectively from 2000 to 2011. Rates were calculated and compared over time by age group and jurisdiction. RESULTS: Since 1993, measles notifications have fallen considerably in Australia. However, between 2000 and 2011, measles notification rates and hospitalisation rates fluctuated. Between 2000 and 2011, there were 990 measles notifications in Australia. The average annual notification rate was 0.4 per 100,000 population. Children aged 0-4 years were the most susceptible group, particularly infants less than 1 year of age (average annual rate, 1.6 per 100,000 population). High incidence was also observed in adolescents (average annual rate, 0.7 per 100,000 population) and young adults (average annual rate, 0.8 per 100,000 population). Jurisdictional variation occurred with differing patterns of notifications and hospitalisations. CONCLUSIONS: Although a marked reduction in measles notifications and hospitalisations has occurred in the past decade, susceptible individuals should be vaccinated to prevent outbreaks and to maintain a low incidence of measles and Australia's elimination status.

Estimating the measles effective reproduction number in Australia from routine notification data.

OBJECTIVE: To estimate the measles effective reproduction number (R) in Australia by modelling routinely collected notification data. METHODS: R was estimated for 2009-2011 by means of three methods, using data from Australia's National Notifiable Disease Surveillance System. Method 1 estimated R as 1 - P, where P equals the proportion of cases that were imported, as determined from data on place of acquisition. The other methods estimated R by fitting a subcritical branching process that modelled the spread of an infection with a given R to the observed distributions of outbreak sizes (method 2) and generations of spread (method 3). Stata version 12 was used for method 2 and Matlab version R2012 was used for method 3. For all methods, calculation of 95% confidence intervals (CIs) was performed using a normal approximation based on estimated standard errors. FINDINGS: During 2009-2011, 367 notifiable measles cases occurred in Australia (mean annual rate: 5.5 cases per million population). Data were 100% complete for importation status but 77% complete for outbreak reference number. R was estimated as < 1 for all years and data types, with values of 0.65 (95% CI: 0.60-0.70) obtained by method 1, 0.64 (95% CI: 0.56-0.72) by method 2 and 0.47 (95% CI: 0.38-0.57) by method 3. CONCLUSION: The fact that consistent estimates of R were obtained from all three methods enhances confidence in the validity of these methods for determining R.

Australia's polio risk.

Australia, like all polio-free countries and regions, remains at risk of a wild poliovirus importation until polio is eradicated globally. The most probable route of importation will be through a traveller arriving in Australia either by air or sea from a polio-endemic or re-infected country. While the overall risk of an imported wild poliovirus infection leading to transmission within Australia is assessed as being low, some areas of the country have been identified as at increased risk. Local areas with relatively high arrivals from polio endemic countries, areas of low vaccination coverage and the potential for transmission to occur when these 2 factors are combined, were identified by this review as Australia's main polio risk. The risk of an importation event leading to locally acquired cases is mitigated by generally high polio vaccination coverage in Australia. This high coverage extends to residents of the Torres Strait Islands who are in close proximity to Papua New Guinea, a country identified as at high risk of poliovirus transmission should an importation occur. In 2012, all states and territories had vaccination coverage of greater than 90% at 1 year of age and all exceeded 93% at 2 years of age. Population immunity to wild poliovirus type 1, which remains the major cause of paralysis globally, has been estimated at 82%. This is sufficient to prevent outbreaks of this type in Australia. Of the 211 eligible non-polio acute flaccid paralysis (AFP) cases classified between 2008 and 2011, 91% (193) were vaccinated against polio at least once. High quality surveillance for AFP, which is supplemented by sentinel enterovirus and environmental surveillance activities, gives confidence that an imported case would be detected and appropriate public health action would ensue.

Australia's notifiable disease status, 2010: annual report of the National Notifiable Diseases Surveillance System.

In 2010, 65 diseases and conditions were nationally notifiable in Australia. States and territories reported a total of 209,079 notifications of communicable diseases to the National Notifiable Diseases Surveillance System, a decrease of 12% on the number of notifications in 2009. This decrease was largely due to a reduction of influenza compared with the influenza A(H1N1) pandemic 2009. In 2010, the most frequently notified diseases were sexually transmissible infections (86,620 notifications, 41.4% of total notifications), vaccine preventable diseases (61,964 notifications, 29.6% of total notifications), and gastrointestinal diseases (31,548 notifications, 15.1% of total notifications). There were 18,302 notifications of bloodborne diseases; 8,244 notifications of vectorborne diseases; 1,866 notifications of other bacterial infections; 532 notifications of zoonoses and 3 notifications of quarantinable diseases.

Measles control in Australia - threats, opportunities and future needs.

Control of measles was the focus of a national workshop held in 2015 in Sydney, Australia, bringing together stakeholders in disease control and immunisation to discuss maintaining Australia's measles elimination status in the context of regional and global measles control. The global epidemiology of measles was reviewed, including outbreaks in countries that have achieved elimination, such as the Disneyland outbreak in the United States and large outbreaks in Sydney, Australia. Transmission of measles between Australia and New Zealand occurs, but has not been a focus of control measures. Risk groups, the genetic and seroepidemiology of measles as well as surveillance, modelling and waning vaccine-induced immunity were reviewed. Gaps in policy, research and practice for maintaining measles elimination status in Australia were identified and recommendations were developed. Elimination of measles globally is challenging because of the infectiousness of measles and the need for 2-dose vaccine coverage rates in excess of 95% in all countries to achieve it. Until this occurs, international travel will continue to permit measles importation from endemic countries to countries that have achieved elimination. When measles cases are imported, failure to diagnose and isolate cases places the health system at risk of measles outbreaks. Vaccine funding models can result in gaps in vaccine coverage for adults and migrants. Australia introduced a whole-of-life immunisation register in 2016 and catch-up vaccination for at-risk communities, which will improve measles control. Research on diagnosis, immunology, case management and modelling of vaccination strategies are important to ensure continued control of measles.

'Silent' and 'noisy' areas: acute flaccid paralysis surveillance at subnational level, Australia, 2001-2015.

Background: Acute flaccid paralysis (AFP) surveillance rates are used as an indicator of surveillance sensitivity to detect poliomyelitis with an expected rate of ≥1 case per 100 000 population in children under 15 years of age. Methods: The Australian AFP detection rates at sub-national (statistical local area) level were analysed using χ2 goodness of fit tests and exact Poisson probabilities for the combined years 2001-2015 to detect 'silent areas', which may require improved AFP detection efforts, and areas with greater than expected rates, which may indicate unexplained clusters such as those due to enterovirus infection. Results: Eight (n=8/87, 9%) local areas had AFP surveillance detection rates that were less than expected, and eighteen local areas (n=18/87, 21%) had rates that were greater than expected. However, based on available evidence, it is unlikely that these indicated previously unidentified, enterovirus clusters. Conclusions: While Australia has regularly met the national AFP surveillance performance indicators, at the subnational level nine per cent of local areas demonstrated statistically significant lower AFP detection rates. All countries, even those with relatively small populations, should actively identify silent AFP areas to prompt surveillance improvements.

Australia's notifiable disease status, 2009: annual report of the National Notifiable Diseases Surveillance System.

In 2009, 65 diseases and conditions were nationally notifiable in Australia. States and territories reported a total of 236,291 notifications of communicable diseases to the National Notifiable Diseases Surveillance System, an increase of 48% on the number of notifications in 2008. This increase was largely due to cases of influenza A(H1N1) pandemic 2009. In 2009, the most frequently notified diseases were vaccine preventable diseases (101,627 notifications, 43% of total notifications), sexually transmissible infections (73,399 notifications, 31% of total notifications), and gastrointestinal diseases (31,697 notifications, 13% of total notifications). There were 18,861 notifications of bloodborne diseases; 8,232 notifications of vectorborne diseases; 1,919 notifications of other bacterial infections; 552 notifications of zoonoses and 4 notifications of quarantinable diseases.

Contact tracing of in-flight measles exposures: lessons from an outbreak investigation and case series, Australia, 2010.

OBJECTIVE: To describe a 2010 outbreak of nine cases of measles in Australia possibly linked to an index case who travelled on an international flight from South Africa while infectious. METHODS: Three Australian state health departments, Victoria, Queensland and New South Wales, were responsible for the investigation and management of this outbreak, following Australian public health guidelines. RESULTS: An outbreak of measles occurred in Australia after an infectious case arrived on a 12-hour flight from South Africa. Only one of four cases in the first generation exposed to the index case en route was sitting within the two rows recommended for contact tracing in Australian and other guidelines. The remaining four cases in subsequent generations, including two health care workers, were acquired in health care settings. Seven cases were young adults. Delays in diagnosis and notification hampered disease control and contact tracing efforts. CONCLUSION: Review of current contact tracing guidelines following in-flight exposure to an infectious measles case is required. Alternative strategies could include expanding routine contact tracing beyond the two rows on either side of the case's row or expansion on a case-by-case basis depending on cabin layout and case and contact movements in flight. Releasing information about the incident by press release or providing generic information to everyone on the flight using e-mail or text messaging information obtained from the relevant airline, may also be worthy of consideration. Disease importation, inadequately vaccinated young adults and health care-related transmission remain challenges for measles control in an elimination era.

Australia's notifiable disease status, 2008: annual report of the National Notifiable Diseases Surveillance System.

In 2008, 65 communicable diseases and conditions were nationally notifiable in Australia. States and territories reported a total of 160,508 notifications of communicable diseases to the National Notifiable Diseases Surveillance System, an increase of 9% on the number of notifications in 2007. In 2008, the most frequently notified diseases were sexually transmissible infections (69,459 notifications, 43% of total notifications), vaccine preventable diseases (34,225 notifications, 21% of total notifications) and gastrointestinal diseases (27,308 notifications, 17% of total notifications). There were 18,207 notifications of bloodborne diseases; 8,876 notifications of vectorborne diseases; 1,796 notifications of other bacterial infections; 633 notifications of zoonoses and 4 notifications of quarantinable diseases.

Australia's notifiable disease status, 2007: annual report of the National Notifiable Diseases Surveillance System.

In 2007, 69 diseases and conditions were nationally notifiable in Australia. States and territories reported a total of 146,991 notifications of communicable diseases to the National Notifiable Diseases Surveillance System, an increase of 5% on the number of notifications in 2006. In 2007, the most frequently notified diseases were sexually transmissible infections (62,474 notifications, 43% of total notifications), gastrointestinal diseases (30,325 notifications, 21% of total notifications) and vaccine preventable diseases (25,347 notifications, 17% of total notifications). There were 19,570 notifications of bloodborne diseases; 6,823 notifications of vectorborne diseases; 1,762 notifications of other bacterial infections; 687 notifications of zoonoses and 3 notifications of quarantinable diseases.