Obstetric and Neonatal Invasive Meningococcal Disease Caused by Neisseria meningitidis Serogroup W, Western Australia, Australia.

Three mother-baby pairs with invasive meningococcal disease occurred over 7 months in Western Australia, Australia, at a time when serogroup W sequence type 11 clonal complex was the predominant local strain. One mother and 2 neonates died, highlighting the role of this strain as a cause of obstetric and early neonatal death.

A protracted mumps outbreak in Western Australia despite high vaccine coverage: a population-based surveillance study.

BACKGROUND: In 2007-08, a genotype J mumps outbreak occurred among Aboriginal people in northern Western Australia, despite high vaccine coverage. In March, 2015, a second protracted mumps outbreak occurred in northern Western Australia and spread widely across rural areas of the state. This time the outbreak was caused by a genotype G virus and again primarily affected Aboriginal people. We aimed to describe the epidemiology of this outbreak. METHODS: In this population-based surveillance study, we analysed statutory notifications and public health case follow-up data from the Western Australia Notifiable Infectious Diseases Database and vaccination information from the Australian Childhood Immunisation Register. An outbreak case of mumps was notified if the affected person was living in or visiting a community in Western Australia where there was active mumps transmission, and if mumps infection was confirmed by laboratory diagnosis or by an epidemiological link. We analysed case demographics, vaccination status, and age-standardised attack rates in Aboriginal and non-Aboriginal people by region of notification. Laboratory diagnoses were made by real-time RT-PCR, serology, or both, and carried out by the sole public pathology provider in Western Australia. FINDINGS: Between March 1, 2015, and December 31, 2016, 893 outbreak cases were notified. 798 (89%) of 893 outbreak cases were reported in Aboriginal people. 40 (4%) of 893 people were admitted to hospital, and 33 (7%) of 462 men reported orchitis. Mumps attack rates increased sharply with age, peaking in the 15-19 age group. 371 (89%) of 419 people aged 1-19 years were fully vaccinated and 29 (7%) were partly vaccinated. Of the 240 people who tested positive by real-time RT-PCR and had also been tested for mumps-specific IgG and IgM, 165 (69%) were positive for IgG but negative for IgM, indicating the importance of RT-PCR testing for diagnosis in vaccinated populations. None of the cases from the 2007-08 genotype J outbreak were re-notified. INTERPRETATION: The number of mumps outbreaks reported in recent years among highly vaccinated populations, including Indigenous populations, has been growing. More widespread and pre-emptive use of the third dose of measles, mumps, and rubella vaccine might be required to control and prevent future outbreaks in high-risk populations. Research should explore the benefit of increasing the intervals between vaccine doses to strengthen the durability of vaccine protection. FUNDING: None.

Legionnaires' Disease Outbreak on a Merchant Vessel, Indian Ocean, Australia, 2015.

Two cases of Legionnaires' disease and 1 of Pontiac fever occurred among the crew of a merchant ship operating off the shores of Australia. PCR assays identified potential sources in the ship's cabins. Modification of maritime regulations for Legionnaires' disease prevention in commercial vessels is needed for nonpassenger merchant ships.

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.

The impact of parental postpartum pertussis vaccination on infection in infants: A population-based study of cocooning in Western Australia.

During a pertussis epidemic in 2011-2012 the Western Australian (WA) Department of Health implemented a 'cocooning' programme, offering free pertussis-containing vaccine (dTpa) to new parents. We assessed the impact of vaccinating parents with dTpa on the incidence of pertussis infection in newborns. Births in WA during 2011-2012 were linked to a register of parental pertussis vaccinations and to notified reports of laboratory-proven pertussis in children <6 months of age. Parents who received dTpa during the four weeks after their child's birth were defined as 'vaccinated postpartum.' Cox proportional-hazards methods were used to calculate hazard ratios (HRs) and 95% confidence intervals (CIs) for the risk of pertussis infection among infants born to parents vaccinated postpartum vs. unvaccinated parents, adjusted for maternal age, geographic region, timing of birth, and number of siblings. Of 64,364 live-births, 43,480 (68%) infants had at least one vaccinated parent (60% of mothers and 36% of fathers). After excluding records where parent(s) were either vaccinated prior to the birth, vaccinated >28 days after the birth, the vaccination date was uncertain, or the child died at birth (n=42), the final cohort contained 53,149 children, 118 of whom developed pertussis. There was no difference in the incidence of pertussis among infants whose parents were both vaccinated postpartum compared to those with unvaccinated parents (1.9 vs 2.2 infections per 1000 infants; adjusted HR 0.91; 95%CI 0.55-1.53). Similarly, when assessed independently, maternal postpartum vaccination was not protective (adjusted HR 1.19; 95%CI 0.82-1.72). Supplemental sensitivity analyses which varied the time period for parental vaccination and accounted for under-reporting of vaccination status did not significantly alter these findings. In our setting, vaccinating parents with dTpa during the four weeks following delivery did not reduce pertussis diagnoses in infants. WA now provides dTpa vaccine to pregnant women during the third trimester.

Influenza vaccine effectiveness estimates for Western Australia during a period of vaccine and virus strain stability, 2010 to 2012.

During 2010-2012 the strain composition of the influenza vaccine in the Southern Hemisphere did not change, but the circulating virus type/subtype did. We pooled data for these years from the Western Australian sentinel medical practice surveillance system for influenza to estimate vaccine effectiveness (VE) by influenza virus type and subtype. A case test-negative design was used with VE estimated as (1-odds ratio)×100%. There were 2182 patients included in the analysis across the 3 years studied. The predominant subtype was A/H1pdm09 in 2010 and 2011, and A/H3 in 2012. The overall adjusted VE estimate against all influenza for 2010-2012 was 51% (95% CI: 36, 63). Estimates were highest against A/H1pdm09 at 74% (95% CI: 47, 87), followed by 56% (95% CI: 33, 71) for influenza B and lowest against A/H3 at 39% (95% CI: 13, 57). When analyses were restricted to compare influenza-positive patients with patients who tested positive for a non-influenza virus, overall adjusted VE was 59% (95% CI: 39, 72). These results suggest moderate protection against influenza by vaccination in Western Australia over the period 2010-2012, and are consistent with findings from other settings.

Risk of measles transmission on aeroplanes: Australian experience 2007-2011.

OBJECTIVE: To quantify the risk of transmission of measles associated with infectious people who travelled on aeroplane flights to or within Australia. DESIGN, SETTING AND SUBJECTS: Data were obtained from state and territory health authorities on all measles notifications from January 2007 to June 2011 for people who were likely to have been infectious or infected while travelling on aeroplanes in Australia. RESULTS: Forty-five infectious people travelled on aeroplanes. Twenty secondary infections occurred in people on seven of 49 flights (14%; 95% CI, 6%-29%), comprising 19% (95% CI, 8%-40%) of the 36 international flights and none of 13 (95% CI, 0-28%) domestic flights that carried infectious people. Secondary infections occurred in nine people who were seated within two rows of the index case and in 11 people who were seated outside of two rows. Secondary transmission was more likely to occur with younger index cases (P = 0.025) and when there were multiple infectious people travelling (P = 0.018). About a third(15/49) of flight manifests were available to health authorities within 5 days oftravel. CONCLUSION: Despite secondary measles transmission occurring on 19% of international flights carrying infectious people, risk was not clearly related to seating proximity, and contact tracing was ineffective, especially given delays in diagnosis, notification and accessing flight manifests. We recommend that direct contact tracing to identify susceptible people exposed to people infected with measles on aeroplane flights should not be undertaken routinely, and other strategies should be considered.

Seroepidemiologic effects of influenza A(H1N1)pdm09 in Australia, New Zealand, and Singapore.

To estimate population attack rates of influenza A(H1N1)pdm2009 in the Southern Hemisphere during June-August 2009, we conducted several serologic studies. We pooled individual-level data from studies using hemagglutination inhibition assays performed in Australia, New Zealand, and Singapore. We determined seropositive proportions (titer ≥40) for each study region by age-group and sex in pre- and postpandemic phases, as defined by jurisdictional notification data. After exclusions, the pooled database consisted of, 4,414 prepandemic assays and 7,715 postpandemic assays. In the prepandemic phase, older age groups showed greater seropositive proportions, with age-standardized, community-based proportions ranging from 3.5% in Singapore to 11.9% in New Zealand. In the postpandemic phase, seropositive proportions ranged from 17.5% in Singapore to 30.8% in New Zealand, with highest proportions seen in school-aged children. Pregnancy and residential care were associated with lower postpandemic seropositivity, whereas Aboriginal and Torres Strait Islander Australians and Pacific Peoples of New Zealand had greater postpandemic seropositivity.

Geographic Information Systems used to describe the link between the risk of Ross River virus infection and proximity to the Leschenault estuary, WA.

OBJECTIVE: To investigate the relationship between risk of Ross River virus (RRV) infection and proximity to mosquito-breeding habitat surrounding a tidal wetland ecosystem in south-west Australia. METHODS: Geographic information systems (GIS) were used to spatially map cases of RRV disease in the Leschenault region between July 1995 and June 1996. Half kilometre buffer zones were constructed around the Leschenault Estuary and associated waterways; RRV disease case counts were calculated for each zone. RESULTS: Different relationships between RRV disease incidence and proximity to saltmarsh mosquito habitat were observed east of the Leschenault Estuary compared with an urban region to the south. Disease incidence showed a decreasing trend away from eastern margins of the Estuary, particularly for the first 2 km. In the urban region, RRV disease risk was low close to the Estuary, but increased further out and remained steady across the remainder of that region. CONCLUSIONS: The findings support an increased risk of contracting RRV disease for people residing close to eastern margins of the Leschenault Estuary. IMPLICATIONS: This study highlights how historical data combined with GIS can improve understanding of the epidemiology of RRV disease. This has a valuable role in assessing the risk of mosquito-borne disease for land-use planning.

Chronic disease and hospitalisation for pandemic (H1N1) 2009 influenza in Indigenous and non-Indigenous Western Australians.

Indigenous and non-indigenous Western Australians with pandemic (H1N1) 2009 influenza (pH1N1) infection were compared for risk factors, influenza vaccination history, symptoms, use of antiviral medications, and hospitalisation. Data were collected systematically on 856 notified cases with laboratory confirmed pH1N1 infection during the first 10 weeks of pH1N1 virus transmission in Western Australia in 2009. Indigenous people with pH1N1 were approximately 3 times more likely to be hospitalised and were more likely to have a range of underlying medical conditions and be smokers, compared with non-Indigenous cases. Age (P < 0.001) and the presence of two or more co-morbidities (P < 0.001) were independent predictors of hospitalisation, while Indigenous status was not, indicating that higher pH1N1 hospitalisation rates in Indigenous Australians during the 2009 winter season were attributable to the higher prevalence of underlying chronic disease. These results underscore the need to ensure that influenza vaccination is delivered as widely as possible among those with chronic health conditions.

Hepatitis B outbreak following a mass-casualty incident, Australia.

On 16 April 2009, a boat carrying 47 Afghan asylum seekers and 2 Indonesian crew exploded in Australian waters, resulting in mass casualties. Of these casualties, 23 persons who suffered significant burns were transferred to Royal Perth Hospital, Perth, Western Australia. One patient was subsequently shown to be a hepatitis B virus (HBV) carrier at the time of the explosion. Over the following months, 3 other patients received a diagnosis of acute hepatitis B, and an additional 4 patients showed serological evidence of recent HBV infection, including 1 patient who was transferred to another Australian city. Molecular typing determined that the strains from the HBV carrier and the acute and recent case patients formed a closely related cluster, and the investigation suggested that transmission occurred at or around the time of the boat explosion. This is the first report of confirmed transmission of HBV following a disaster, and it reinforces the importance of postexposure prophylaxis for HBV in mass casualty situations.

We should not be complacent about our population-based public health response to the first influenza pandemic of the 21st century.

BACKGROUND: More than a year after an influenza pandemic was declared in June 2009, the World Health Organization declared the pandemic to be over. Evaluations of the pandemic response are beginning to appear in the public domain. DISCUSSION: We argue that, despite the enormous effort made to control the pandemic, it is now time to acknowledge that many of the population-based public health interventions may not have been well considered. Prior to the pandemic, there was limited scientific evidence to support border control measures. In particular no border screening measures would have detected prodromal or asymptomatic infections, and asymptomatic infections with pandemic influenza were common. School closures, when they were partial or of short duration, would not have interrupted spread of the virus in school-aged children, the group with the highest rate of infection worldwide. In most countries where they were available, neuraminidase inhibitors were not distributed quickly enough to have had an effect at the population level, although they will have benefited individuals, and prophylaxis within closed communities will have been effective. A pandemic specific vaccine will have protected the people who received it, although in most countries only a small minority was vaccinated, and often a small minority of those most at risk. The pandemic vaccine was generally not available early enough to have influenced the shape of the first pandemic wave and it is likely that any future pandemic vaccine manufactured using current technology will also be available too late, at least in one hemisphere. SUMMARY: Border screening, school closure, widespread anti-viral prophylaxis and a pandemic-specific vaccine were unlikely to have been effective during a pandemic which was less severe than anticipated in the pandemic plans of many countries. These were cornerstones of the population-based public health response. Similar responses would be even less likely to be effective in a more severe pandemic. We agree with the recommendation from the World Health Organisation that pandemic preparedness plans need review.

Incidence of pandemic (H1N1) 2009 influenza infection in children and pregnant women during the 2009 influenza season in Western Australia - a seroprevalence study.

OBJECTIVE: To determine antibody levels and estimate incidence of infection with pandemic (H1N1) 2009 influenza in children and pregnant women during the 2009 winter in Western Australia. DESIGN, SETTING AND PARTICIPANTS: Two cross-sectional serosurveys using stored specimens collected for unrelated pathology testing, from before and after (3 August to 30 November 2009) circulation of the pandemic virus, and before commencement of the pandemic vaccination program. Specimens were from three groups: children aged 1-4 years, older children and teenagers aged 5-19 years, and pregnant women aged 21-45 years. The groups were geographically representative of the WA population. MAIN OUTCOME MEASURES: Reactivity against pandemic (H1N1) 2009 and seasonal A(H1N1) influenza viruses measured using haemagglutination inhibition (HI) assays. RESULTS: Antibody titres were determined for 648 individuals in the prepandemic period and 736 in the postpandemic period. In the prepandemic period, HI titres ≥ 40 against the pandemic virus were found in 0 (95% CI, 0.0%-1.6%) children aged 1-4 years, 8.3% (95% CI, 5.3%-12.7%) of older children and teenagers, and 4.5% (95% CI, 2.4%-8.3%) of pregnant women. In postpandemic specimens collected from 1 September 2009 (when influenza activity had declined to near-baseline levels), estimated infection rates (subtracting prepandemic levels) were 25.4% (95% CI for difference, 18.6%-33.4%) in 1-4-year-old children, 39.4% (95% CI, 29.8%-48.5%) in older children and teenagers, and 10.2% (95% CI, 4.1%-17.1%) in pregnant women. CONCLUSIONS: A quarter of preschool children and about 40% of school-aged children and older teenagers had serological evidence of pandemic influenza infection during winter 2009, indicating high levels of mild or asymptomatic infection. The infection rate in pregnant women was much lower. The high infection rates in children help explain the reduced impact of the pandemic virus during the 2010 winter. Augmented by vaccination, there should be sufficiently high levels of immunity in the Australian population to significantly reduce the impact of the virus in future influenza seasons.

Response to pandemic (H1N1) 2009 influenza in Australia - lessons from a State health department perspective.

This article reviews the lessons that can be learned by the health sector, in particular, and the public sector, more generally, from the governmental response to pandemic (H1N1) 2009 influenza A (pH1N1) in Australia during 2009. It covers the period from the emergence of the epidemic to the release of the vaccine, and describes a range of impacts on the Western Australian health system, the government sector and the community. There are three main themes considered from a State government agency perspective: how decisions were influenced by prior planning; how the decision making and communication processes were intimately linked; and the interdependent roles of States and the Commonwealth Government in national programs. We conclude that: (a) communications were generally effective, but need to be improved and better coordinated between the Australian Government, States and general practice; (b) decision making was appropriately flexible, but there needs to be better alignment with expert advice, and consideration of the need for a national disease control agency in Australia; and (c) national funding arrangements need to fit with the model of state-based service delivery and to support critical workforce needs for surge capacity, as well as stockpile and infrastructure requirements.

Comparison of pandemic (H1N1) 2009 and seasonal influenza, Western Australia, 2009.

We compared confirmed pandemic (H1N1) 2009 influenza and seasonal influenza diagnosed in Western Australia during the 2009 influenza season. From 3,178 eligible reports, 984 pandemic and 356 seasonal influenza patients were selected; 871 (88.5%) and 288 (80.9%) were interviewed, respectively. Patients in both groups reported a median of 6 of 11 symptoms; the difference between groups in the proportion reporting any given symptom was < or =10%. Fewer than half the patients in both groups had > or =1 underlying condition, and only diabetes was associated with pandemic (H1N1) 2009 influenza (odds ratio [OR] 1.9, 95% confidence interval [CI] 1.1-3.5). A total of 129 (14.8%) persons with pandemic (H1N1) 2009 and 36 (12.5%) persons with seasonal influenza were hospitalized (p = 0.22). After controlling for age, we found that patient hospitalization was associated with pandemic (H1N1) 2009 influenza (OR 1.5; 95% CI 1.1-2.1). Contemporaneous pandemic and seasonal influenza infections were substantially similar in terms of patients' symptoms, risk factors, and proportion hospitalized.

Pandemic (H1N1) 2009 influenza community transmission was established in one Australian state when the virus was first identified in North America.

BACKGROUND: In mid-June 2009 the State of Victoria in Australia appeared to have the highest notification rate of pandemic (H1N1) 2009 influenza in the world. We hypothesise that this was because community transmission of pandemic influenza was already well established in Victoria at the time testing for the novel virus commenced. In contrast, this was not true for the pandemic in other parts of Australia, including Western Australia (WA). METHODS: We used data from detailed case follow-up of patients with confirmed infection in Victoria and WA to demonstrate the difference in the pandemic curve in two Australian states on opposite sides of the continent. We modelled the pandemic in both states, using a susceptible-infected-removed model with Bayesian inference accounting for imported cases. RESULTS: Epidemic transmission occurred earlier in Victoria and later in WA. Only 5% of the first 100 Victorian cases were not locally acquired and three of these were brothers in one family. By contrast, 53% of the first 102 cases in WA were associated with importation from Victoria. Using plausible model input data, estimation of the effective reproductive number for the Victorian epidemic required us to invoke an earlier date for commencement of transmission to explain the observed data. This was not required in modelling the epidemic in WA. CONCLUSION: Strong circumstantial evidence, supported by modelling, suggests community transmission of pandemic influenza was well established in Victoria, but not in WA, at the time testing for the novel virus commenced in Australia. The virus is likely to have entered Victoria and already become established around the time it was first identified in the US and Mexico.

Household responses to pandemic (H1N1) 2009-related school closures, Perth, Western Australia.

School closure is often purported to reduce influenza transmission, but little is known about its effect on families. We surveyed families affected by pandemic (H1N1) 2009-related school closures in Perth, Western Australia, Australia. Surveys were returned for 233 (58%) of 402 students. School closure was deemed appropriate by 110 parents (47%); however, 91 (45%) parents of 202 asymptomatic students reported taking >or=1 day off work to care for their child, and 71 (35%) had to make childcare arrangements because of the class closures. During the week, 172 (74%) students participated in activities outside the home on >or=1 occasion, resulting in an average of 3.7 out-of-home activities for each student. In our survey, activities outside the home were commonly reported by students affected by school closure, the effect on families was substantial, and parental opinion regarding school closures as a means to mitigate the outbreak of pandemic (H1N1) 2009 was divided.