Drivers of the summer influenza epidemic in New South Wales, 2018-19.

OBJECTIVES: To assess the extent to which the 2018-19 New South Wales summer influenza epidemic was associated with overseas or domestic travel and with seasonal influenza vaccination status. DESIGN, SETTING: Unmatched case-control study, based on an online survey distributed from the NSW Notifiable Conditions Information Management System (NCIMS) to people for whom mobile phone numbers were available. PARTICIPANTS: A case was defined as a person with notified laboratory-confirmed influenza with onset of illness between 1 December 2018 and 21 March 2019. People with notified pertussis infections (confirmed or probable) were selected as controls. MAIN OUTCOME MEASURES: Notified influenza infection, by travel and contact with unwell overseas travellers in the week before onset of illness and seasonal influenza vaccination status (as the primary exposures). RESULTS: Valid survey responses were provided by 648 of 2806 invited people with notified influenza (23%) and 257 of 796 invited people with notified pertussis (32%). The demographic characteristics of the respondents were similar to those of the source population (7251 cases, 2254 controls). During the first two months of the summer of 2018-19, notified influenza was more likely for people who had travelled overseas or had contact with an ill overseas traveller in the week before symptom onset (adjusted OR [aOR], 6.99; 95% CI, 3.59-13.6), but not during the second two months (aOR, 1.63; 95% CI, 0.79-3.35). Influenza vaccination status was not associated with the likelihood of notified influenza. CONCLUSIONS: Travel-related factors were early drivers of the 2018-19 NSW summer influenza epidemic; local transmission sustained the outbreak despite unfavourable conditions later in summer. Our findings prompted re-evaluation of recommendations for pre-travel vaccination in NSW. The role of travel in out-of-season influenza outbreaks should be considered in other temperate zones.

Examining the use of antiviral prophylaxis for influenza outbreaks in residential aged care facilities in NSW, Australia.

BACKGROUND: Influenza attack rates in closed population settings, such as residential aged care facilities (RACFs), can be more than 50% during annual epidemics. Uncertainty about the effectiveness of neuraminidase inhibitors (NAIs) as prophylaxis for influenza outbreaks has led to variations in their use in RACFs in New South Wales (NSW), Australia. OBJECTIVES: To examine the use of prophylactic NAIs by NSW RACFs for residents during influenza outbreaks in the 2015 influenza season. METHODS: A prospective cohort study of influenza outbreaks reported to NSW Public Health Units from 1 June 2015 - 31 October 2015. RESULTS: Eighty-eight RACFs reported influenza outbreaks; 86 were included in the study. Fifty-two RACFs used prophylactic NAIs; 34 did not. The median time to start NAI prophylaxis from the onset date of the first case was 8.5 days (range 2-23). The average proportion of residents within a facility that received prophylaxis was 51%percnt; (range 0.7-95). CONCLUSION: Variations in the use of prophylactic NAIs exist across RACFs. Earlier initiation of NAI prophylaxis, improved resident coverage where appropriate and other practice changes are recommended for the management of influenza outbreaks in RACFs.

Monitoring travellers from Ebola-affected countries in New South Wales, Australia: what is the impact on travellers?

BACKGROUND: Amidst an Ebola virus disease (EVD) epidemic of unprecedented magnitude in west Africa, concerns about the risk of importing EVD led to the introduction of programs for the screening and monitoring of travellers in a number of countries, including Australia. Emerging reports indicate that these programs are feasible to implement, however rigorous evaluations are not yet available. We aimed to evaluate the program of screening and monitoring travellers in New South Wales. METHODS: We conducted a mixed methods study to evaluate the program of screening and monitoring travellers in New South Wales. We extracted quantitative data from the Notifiable Conditions Information Management System database and obtained qualitative data from two separate surveys of public health staff and arrivals, conducted by phone. RESULTS: Between 1 October 2014 and 13 April 2015, public health staff assessed a total of 122 out of 123 travellers. Six people (5%) developed symptoms compatible with EVD and required further assessment. None developed EVD. Aid workers required lower levels of support compared to other travellers. Many travellers experienced stigmatisation. Public health staff were successful in supporting travellers to recognise and manage symptoms. CONCLUSION: We recommend that programs for monitoring travellers should be tailored to the needs of different populations and include specific strategies to remediate stigmatisation.

Strengthening public health systems: assessing the attributes of the NSW influenza surveillance system.

OBJECTIVE: In New South Wales (NSW), influenza surveillance is informed by a number of discrete data sources, including laboratories, emergency departments, death registrations and community surveillance programs. The purpose of this study was to evaluate the NSW influenza surveillance system using the US Centers for Disease Control and Prevention guidelines for evaluating public health surveillance systems. Importance of study: Having a strong influenza surveillance system is important for both seasonal and pandemic influenza preparedness. The findings will inform recommendations for strengthening surveillance in NSW. METHODS: The scope was limited to all sources included in the NSW Health Influenza Report in 2012-13. To assess the performance of the system, in-depth interviews (N = 21) were conducted with key stakeholders and thematically analysed. Respiratory testing data gathered through the sentinel laboratories in 2012 were used to estimate sensitivity, and laboratory notifications were analysed to assess timeliness and representativeness. Key documents - including reports, guidelines, correspondence and meeting minutes - were also reviewed, providing a method of triangulation. RESULTS: The NSW influenza surveillance system integrates multiple sources of surveillance of influenza and influenza-like illness to provide a comprehensive picture of influenza in the community. Despite its structural complexity, the system delivers quality, timely and relevant data to inform a range of public health activities, and the NSW Health Influenza Report is well regarded by stakeholders. Challenges include managing system complexity, key person risk and cross-jurisdictional issues. Stakeholders commented that system flexibility would depend on additional resourcing. Although the sensitivity of sentinel laboratory surveillance was estimated as 1-25%, depending on the time of year, understanding sensitivity remains a challenge in influenza surveillance where the true incidence of infection is unknown. CONCLUSION: Influenza surveillance is critical for monitoring virological changes, understanding disease epidemiology and informing public health responses. The system was found to deliver timely and good-quality surveillance information. Additional value could be achieved by increasing flexibility and stability, automating systems (where possible) and formalising processes of data acquisition. The system continues to negotiate a number of constraints, including complexity and cross-jurisdictional issues, which are ongoing obstacles to realising some potential system improvements.

An outbreak of enterovirus 71 in metropolitan Sydney: enhanced surveillance and lessons learnt.

OBJECTIVE: To report the findings of the enhanced surveillance set up in New South Wales in response to the recent outbreak of human enterovirus 71 (EV71) infection. DESIGN AND SETTING: A two-armed enhanced public health surveillance system including statewide emergency department surveillance and clinical surveillance at the Sydney Children's Hospitals Network. PARTICIPANTS: Children aged less than 10 years with suspected or confirmed enterovirus infection. MAIN OUTCOME MEASURES: Epidemiology of the outbreak, including weekly case counts, demographic information, geographic spread of the outbreak, and clinical presentation and progression. RESULTS: Statewide weekly case counts indicate that an epidemic of EV71 infection occurred in NSW from December 2012 until May 2013. Around 119 children were reported with disease severe enough to warrant admission to a tertiary Sydney children's hospital. Cases were spread throughout the Sydney metropolitan area and there is some evidence of geographic migration of the outbreak. Presenting features included fever, lethargy, myoclonus and skin rash. Only 24% of cases presented with classical hand, foot and mouth disease. CONCLUSIONS: EV71 infection is likely to continue to be a public health problem in Australia. Surveillance of routinely collected emergency department data can provide a useful indication of its activity in the community.

Field effectiveness of hepatitis A vaccine and uptake of post exposure prophylaxis following a change to the Australian guidelines.

BACKGROUND: In 2009, national guidelines for hepatitis A control in Australia changed to recommend hepatitis A vaccine (HAV), instead of normal human immune globulin (NHIG), for post-exposure prophylaxis (PEP). AIMS: (1) Determine whether the uptake of PEP among contacts of hepatitis A cases changed after the introduction of the new guidelines, and (2) assess the field effectiveness of the HAV used as PEP in preventing infection among contacts of hepatitis A cases. METHODS: A retrospective cohort of contacts from hepatitis A cases reported to metropolitan Public Health Units in Sydney, Australia, between October 2008 and June 2010, was identified. Contacts were analysed by time period, age, PEP type, and susceptibility to hepatitis A. The relative risk (RR) of hepatitis A infection among susceptible contacts who received HAV, compared with susceptible contacts who had not received HAV, was calculated to estimate the effectiveness of the HAV when used as PEP. RESULTS: The uptake of PEP by susceptible contacts increased from 76% (n=133) to 89% (n=127) after the introduction of the new guidelines. Before the change in guidelines, no one who received PEP was later reported with hepatitis A. After the change in guidelines, one of the 123 contacts who received HAV as PEP was subsequently reported with hepatitis A. However, this case was likely to have been co-exposed with a primary case. Conservatively, assuming this was a secondary case, the vaccine effectiveness of HAV was 95.6% (66.1%-99.4%). Nine of 10 incident cases of hepatitis A were contacts who did not receive any PEP. CONCLUSION: The improved uptake of PEP and the high estimate of the effectiveness of HAV provides support for using HAV for PEP. The very high occurrence of hepatitis A among contacts who did not receive any PEP further highlights the importance of PEP in preventing hepatitis A infection.

Infectious diseases in returned travellers, NSW, 2010-2011.

AIM: To quantify the proportion of selected notified diseases in NSW attributable to overseas travel and assess the quality of data on travel-associated risk factors, to inform prevention strategies. METHODS: 2010 and 2011 notification data for dengue, hepatitis A, hepatitis E, malaria, paratyphoid fever, shigellosis and typhoid fever were extracted from the NSW Notifiable Conditions Information Management System and analysed for travel-associated risk factors. RESULTS: Where place of acquisition was known, the proportion of cases for whom the disease was acquired overseas ranged from 48.7% for shigellosis to 100% for hepatitis E, malaria and typhoid. Over half of hepatitis A (53.3%), hepatitis E (74.2%), malaria (54.5%), paratyphoid (53.3%) and typhoid (65.7%) cases were associated with travel to the person's country of birth. Hepatitis A vaccination rates were significantly lower among overseas-acquired than locally-acquired cases (4.8% vs 22.2%, Χ(2)=6.58, p<0.02). CONCLUSION: A large proportion of selected enteric and vectorborne disease case notifications were associated with overseas travel. All potential travellers should be made aware of the risks and available preventive measures, such as vaccination against hepatitis A and typhoid fever, taking precautions with food and water and use of malaria chemoprophylaxis, where appropriate. Improvements in data on risk factors, reason for travel and barriers to the use of preventive measures would better inform prevention strategies.

Airport arrivals screening during pandemic (H1N1) 2009 influenza in New South Wales, Australia.

OBJECTIVE: To examine the effectiveness of airport screening in New South Wales during pandemic (H1N1) 2009 influenza. DESIGN, SETTING AND PARTICIPANTS: Analysis of data collected at clinics held at Sydney Airport, and of all notified cases of influenza A(H1N1)pdm09, between 28 April 2009 and 18 June 2009. MAIN OUTCOME MEASURES: Case detection rate per 100,000 passengers screened, sensitivity, positive predictive value and specificity of airport screening. The proportion of all cases in the period detected at airport clinics was compared with the proportion detected in emergency departments and general practice. RESULTS: Of an estimated 625,147 passenger arrivals at Sydney Airport during the period, 5845 (0.93%) were identified as being symptomatic or febrile, and three of 5845 were subsequently confirmed to have influenza A(H1N1)pdm09, resulting in a detection rate of 0.05 per 10,000 screened (95% CI, 0.02-1.14 per 10,000). Forty-five patients with overseas-acquired influenza A(H1N1)pdm09 in NSW would have probably passed through the airport during this time, giving airport screening a sensitivity of 6.67% (95% CI, 1.40%-18.27%). Positive predictive value was 0.05% (95% CI, 0.02%-0.15%) and specificity 99.10% (95% CI, 99.00%-100.00%). Of the 557 confirmed cases across NSW during the period, 290 (52.1%) were detected at emergency departments and 135 (24.2%) at general practices, compared with three (0.5%) detected at the airport. CONCLUSIONS: Airport screening was ineffective in detecting cases of influenza A(H1N1)pdm09 in NSW. Its future use should be carefully considered against potentially more effective interventions, such as contact tracing in the community.

The changing epidemiology of Murray Valley encephalitis in Australia: the 2011 outbreak and a review of the literature.

Murray Valley encephalitis virus (MVEV) is the most serious of the endemic arboviruses in Australia. It was responsible for six known large outbreaks of encephalitis in south-eastern Australia in the 1900s, with the last comprising 58 cases in 1974. Since then MVEV clinical cases have been largely confined to the western and central parts of northern Australia. In 2011, high-level MVEV activity occurred in south-eastern Australia for the first time since 1974, accompanied by unusually heavy seasonal MVEV activity in northern Australia. This resulted in 17 confirmed cases of MVEV disease across Australia. Record wet season rainfall was recorded in many areas of Australia in the summer and autumn of 2011. This was associated with significant flooding and increased numbers of the mosquito vector and subsequent MVEV activity. This paper documents the outbreak and adds to our knowledge about disease outcomes, epidemiology of disease and the link between the MVEV activity and environmental factors. Clinical and demographic information from the 17 reported cases was obtained. Cases or family members were interviewed about their activities and location during the incubation period. In contrast to outbreaks prior to 2000, the majority of cases were non-Aboriginal adults, and almost half (40%) of the cases acquired MVEV outside their area of residence. All but two cases occurred in areas of known MVEV activity. This outbreak continues to reflect a change in the demographic pattern of human cases of encephalitic MVEV over the last 20 years. In northern Australia, this is associated with the increasing numbers of non-Aboriginal workers and tourists living and travelling in endemic and epidemic areas, and also identifies an association with activities that lead to high mosquito exposure. This outbreak demonstrates that there is an ongoing risk of MVEV encephalitis to the heavily populated areas of south-eastern Australia.

An update on the epidemiology and key issues associated with the diagnosis and management of Creutzfeldt-Jakob disease cases in NSW.

Creutzfeldt-Jakob disease (CJD) is a fatal disease caused by the accumulation of abnormal prion proteins in neurological tissues. Routine notification data reveal that NSW has similar rates of CJD to other states and territories in Australia; however, it is likely that there is significant under-ascertainment of cases. It is important that clinicians and public health staff remain vigilant for the clinical signs of CJD and understand the limitations of the different diagnostic tests available. This paper provides a brief overview of the epidemiology of CJD in NSW, as well as current issues in the diagnosis and public health investigation of CJD.

EpiReview: Meningococcal disease in NSW, 1991-2011: trends in relation to meningococcal C vaccination.

AIM: To review the epidemiology of invasive meningococcal disease in NSW for the period 1991-2011, in particular since the introduction of the meningococcal C vaccination program in 2003. METHODS: We undertook a descriptive analysis of NSW notifications of invasive meningococcal disease for the period 2003-2011, and explored long-term changes in the epidemiology of invasive meningococcal disease over the period 1991-2011. RESULTS: In the period 2003-2011, there were 1009 notifications of invasive meningococcal disease in NSW, an average annual rate of 1.6 per 100000 population. Notification rates were highest in the 0-4 and 15-19-year age groups (8.5 and 3.6 per 100000 population respectively). In the period 1991-2011, invasive meningococcal disease notifications increased between 1991 and 2000, peaking at 3.8 notifications per 100000 population in 2000. Notifications have decreased since that time to 1.0 per 100000 population in 2011, most markedly for serogroup C disease since the introduction of the meningococcal C vaccination program in 2003. Meningococcal C notifications reduced from 54 in 2002 (0.8 per 100000 population) to two in 2011 (0.03 per 100000 population). Meningococcal C deaths have also decreased, from nine in 2002 to zero in 2011. The greatest reduction in meningococcal C notifications has been in those aged 1-19 years, the target group for the vaccination program. Meningococcal B notifications have also decreased over the study period, however serogroup B remains the predominant serogroup for invasive meningococcal disease in NSW. CONCLUSION: Notification rates of invasive meningococcal disease have decreased in NSW since 2000. Rates of serogroup C disease have decreased since the introduction of the meningococcal C vaccination program in 2003. Most of the burden of invasive meningococcal disease in NSW is now due to serogroup B disease.

EpiReview: Typhoid fever, NSW, 2005-2011.

AIM: To examine trends in the incidence of typhoid fever in NSW to inform the development of prevention strategies. METHODS: Typhoid fever case notification data for the period 2005-2011 were extracted from the NSW Notifiable Conditions Information Management System. Population incidence rates were calculated and analysed by demographic variables. RESULTS: There were 250 case notifications of typhoid fever in NSW from 2005 to 2011, of which 240 are likely to have been acquired overseas. Case notifications remained relatively stable over the review period with the highest rates in Western Sydney Local Health District (10.9 per 100,000 population). Two-thirds (66.4%) of all case notifications are likely to have been acquired in South Asia, and about half of overseas-acquired case notifications were most likely to have been associated with travel to visit friends and relatives. Hospitalisation was required for 79.6% of cases where hospitalisation status was known. Prior typhoid vaccination was reported in 7% of cases in 2010 and 2011 where vaccination status was known. CONCLUSION: While typhoid fever rates remain low in NSW, case notifications of this preventable infection continue to be reported, particularly in travellers visiting friends and relatives in South Asia. Further research to better understand barriers to the use of preventive measures may be useful in targeting typhoid fever prevention messages in high-risk groups, particularly South Asian communities in NSW.

The impact of influenza A(H1N1)pdm09 compared with seasonal influenza on intensive care admissions in New South Wales, Australia, 2007 to 2010: a time series analysis.

BACKGROUND: In Australia, the 2009 epidemic of influenza A(H1N1)pdm09 resulted in increased admissions to intensive care. The annual contribution of influenza to use of intensive care is difficult to estimate, as many people with influenza present without a classic influenza syndrome and laboratory testing may not be performed. We used a population-based approach to estimate and compare the impact of recent epidemics of seasonal and pandemic influenza. METHODS: For 2007 to 2010, time series describing health outcomes in various population groups were prepared from a database of all intensive care unit (ICU) admissions in the state of New South Wales, Australia. The Serfling approach, a time series method, was used to estimate seasonal patterns in health outcomes in the absence of influenza epidemics. The contribution of influenza was estimated by subtracting expected seasonal use from observed use during each epidemic period. RESULTS: The estimated excess rate of influenza-associated respiratory ICU admissions per 100,000 inhabitants was more than three times higher in 2007 (2.6/100,000, 95% CI 2.0 to 3.1) than the pandemic year, 2009 (0.76/100,000, 95% CI 0.04 to 1.48). In 2009, the highest excess respiratory ICU admission rate was in 17 to 64 year olds (2.9/100,000, 95% CI 2.2 to 3.6), while in 2007, the highest excess rate was in those aged 65 years or older (9.5/100,000, 95% CI 6.2 to 12.8). In 2009, the excess rate was 17/100,000 (95% CI 14 to 20) in Aboriginal people and 14/100,000 (95% CI 13 to 16) in pregnant women. CONCLUSION: While influenza was diagnosed more frequently and peak use of intensive care was higher during the epidemic of pandemic influenza in 2009, overall excess admissions to intensive care for respiratory illness was much greater during the influenza season in 2007. Thus, the impact of seasonal influenza on intensive care use may have previously been under-recognised. In 2009, high ICU use among young to middle aged adults was offset by relatively low use among older adults, and Aboriginal people and pregnant women were substantially over-represented in ICUs. Greater emphasis on prevention of serious illness in Aboriginal people and pregnant women should be a priority in pandemic planning.

Trends and risk factors for hepatitis A in NSW, 2000-2009: the trouble with travel.

AIM: To analyse trends in hepatitis A notifications and information on exposure to risk factors, in particular international travel, collected through routine surveillance in NSW. METHODS: Hepatitis A notification data for the period 2000-2009 were extracted from the Notifiable Diseases Database and analysed by age group, gender, area of residence and exposure risk factors, including travel, food eaten and contact with other possible infectious cases. RESULTS: The notification rate for hepatitis A in NSW fell from 3.0 cases per 100000 population in 2000 to 1.4 cases per 100000 population in 2009. Notification rates were highest among people aged 20-24 years and residents of metropolitan Sydney. Travel to a country where hepatitis A is endemic was a risk exposure identified in 43% of cases. CONCLUSION: International travel to highly endemic countries continues to be the most common risk factor for hepatitis A infection notified in NSW despite recommendations that travellers be vaccinated prior to travel to these areas.

EpiReview: notifications of Q fever in NSW, 2001-2010.

UNLABELLED: Q fever is the most frequently notified zoonotic infection in NSW residents. The past decade has seen the introduction of a targeted national Q fever vaccination program. METHODS: We undertook a descriptive analysis of Q fever notifications in NSW, for the period 2001-2010. RESULTS: A total of 1912 cases of Q fever were notified in NSW between 2001 and 2010 (average 2.8 per 100 000 persons per annum). The majority of Q fever cases were reported in men, aged 40-59 years, living in rural NSW and working in agricultural related occupations. CONCLUSION: The results suggest changes in the epidemiology of Q fever in response to the targeted vaccination program.

Infants under 1 year of age have a significant risk of burn injury.

A wealth of data exists concerning paediatric burn epidemiology in general, but very little exists specifically in infants under 1 year of age, a special group in which mobility begins to develop. A retrospective study of all burn admissions of infants under 1 year old to The Welsh Centre for Burns from January 2003 to January 2006 was performed. During the 3-year period there were 104 new burns cases identified which represents 11.8% of all paediatric admissions. 63.5% (66) were treated as inpatients and 36.5% (38) treated as out-patients. Burns increased in frequency with increasing age and occurred mainly in the home. Scalds were the commonest type of burn in 65% (68) whilst the second most common was contact burns which accounted for 30% (31). The most common source of scald was from cups containing hot drinks (39%) and the most common source of contact burn was radiators/hot water pipes (30%). The mean TBSA was 2.3%, (range 0.5-38%). The frequency of burns in the under 1 year old population highlights a need for emphasis of burn prevention directed to this group. Special attention is needed to look at the specific aetiology of these burns. Starting points for prevention should address the number of burns surrounding hot drinks and bottle warming practices in the case of scalds and the dangers of household radiators and hot water pipes in the case of contact burns.