The changing phases of pandemic (H1N1) 2009 in Queensland: an overview of public health actions and epidemiology

Evidence for an increase in the intensity of inter-seasonal influenza, Queensland, Australia, 2009-2019

BACKGROUND

Inter-seasonal influenza cases have been increasing in Australia. Studies of influenza seasonality typically focus on seasonal transmission in temperate regions, leaving our understanding of inter-seasonal epidemiology limited. We aimed to improve understanding of influenza epidemiology during inter-seasonal periods across climate zones, and explored influenza intensity and strain dominance patterns over time.

METHODS

Queensland state-wide laboratory-confirmed influenza notifications and public laboratory influenza test data from 2009-2019 were described by demographics, time period, region and strain type. We compared influenza intensity over time using the WHO Average Curve method to provide thresholds for seasonal and inter-seasonal periods.

RESULTS

Among the 243 830 influenza notifications and 490 772 laboratory tests reported in Queensland between 2009 and 2019, 15% of notifications and 40% of tests occurred during inter-seasonal periods, with 6.3% of inter-seasonal tests positive. Inter-seasonal notifications and tests substantially increased over time and increases in weekly proportions positive and intensity classifications suggested gradual increases in virus activity. Tropical inter-seasonal activity was higher with periods of marked increase. Influenza A was dominant, although influenza B represented up to 72% and 42% of notifications during some seasonal and inter-seasonal periods, respectively.

CONCLUSIONS

Using notification and testing data, we have demonstrated a gradual increase in inter-seasonal influenza over time. Our findings suggest this increase results from an interplay between testing, activity and intensity, and strain circulation. Seasonal intensity and strain circulation appeared to modify subsequent period intensity. Routine year-round surveillance data would provide a better understanding of influenza epidemiology during this infrequently studied inter-seasonal time period.

Dynamic Propagation and Impact of Pandemic Influenza A (2009 H1N1) in Children: A Detailed Review

Influenza is a highly contagious respiratory infection caused by the circulating Swine flu virus. According to the World Health Organization (WHO), the unique blending strain of influenza A H1N1 2009 (Swine Flu) is a pandemic affecting several geographical regions, including India. Previous literature indicates that children are "drivers" of influenza pandemics. At present, satisfactory data were not available to accurately estimate the role of children in the spread of influenza (in particular 2009 pandemic influenza). However, the role of children in the spread of pandemics influenza is unclear. Several studies in children have indicated that the immunization program decreased the occurrence of influenza, emphasizing the significance of communities impacted by global immunization programs. This article provides a brief overview on how children are a key contributor to pandemic Influenza A (2009 H1N1) and we would like to draw your attention to the need for a new vaccine for children to improve disease prevention and a positive impact on the community.

Characteristics and outcome of viral pneumonia caused by influenza and Middle East respiratory syndrome-coronavirus infections: A 4-year experience from a tertiary care center

BACKGROUND

After the emergence of new influenza viruses, the morbidity and mortality of viral pneumonia have received a great attention.

OBJECTIVES

The objective of this study is to describe the epidemiologic, clinical and laboratory changes, and outcomes of viral pneumonia caused by influenza and the Middle East respiratory syndrome-coronavirus (MERS-CoV) infections.

METHODS

In a retrospective cohort study, the medical records of all patients diagnosed with viral pneumonia at Prince Sultan Military Medical City, Riyadh, Saudi Arabia, during the period from January 2012 to December 2015 were screened. Cases who were > 18 years old and were confirmed by a respiratory viral panel to have viral pneumonia either MERS-CoV or influenza viruses were included in the analysis. Sociodemographic, clinical, laboratory, and outcome data were extracted from patients' medical files. The data were analyzed descriptively and inferentially to identify the predictors of poor outcome.

RESULTS

A total of 448 patients with confirmed viral pneumonia were included, of those, 216 (48.2%) were caused by influenza A (non H1N1)/influenza B, 150 (33.5%) by H1N1, and 82 (18.3%) by MERS-CoV. The majority of patients presented with fever (82%), shortness of breath (64%), and flu-like symptoms (54.9%), particularly in MERS-CoV infected cases (92%). The peak incidence of viral pneumonia was in early spring and autumn. The mortality rate was 13.8%, and it was significantly higher among MERS-CoV cases. The predictors of death were age > 65 years, male gender, and associated comorbidities particularly diabetes mellitus, hypertension, and chronic kidney diseases. The number of comorbid illnesses was directly related to the increase in mortality in this group of patients.

CONCLUSION

Viral pneumonia caused by influenza and MERS-CoV carries a high mortality rate, particularly among MERS-CoV infected cases. Old age, male gender, and comorbid illnesses are predictors of poor outcome. Routine testing for newly emergent viruses is warranted for adults who have been hospitalized with pneumonia.

Planning for Pandemics: Lessons From the Past Decade

It is now 10 years since the disease we now know as SARS--severe acute respiratory syndrome--caused more than 700 deaths around the world and made more than 8,000 people ill. More recently, in 2009 the global community experienced the first influenza pandemic of the 21st century--the 2009 H1N1 influenza pandemic. This paper analyses the major developments in international public health law relating to infectious diseases in the period since SARS and considers their implications for pandemic planning.

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.

Safety and tolerability of a 2009 trivalent inactivated split-virion influenza vaccine in infants, children and adolescents

OBJECTIVE

To evaluate the safety of CSL's split-virion inactivated trivalent 2009 Southern Hemisphere formulation influenza vaccine (TIV) in children.

METHODS

We enrolled 1992 healthy children into three groups: Cohorts A, ≥ 6 months to <3 years; B, ≥ 3 years to <9 years; and C, ≥ 9 years to <18 years. Children received one or two doses of 0.25 ml (22.5 μg haemagglutinin) or 0.5 ml (45 μg) TIV, depending on age and prior vaccination history. We collected post-vaccination solicited adverse event (AE) data (days 0-6), including fever (temperature: ≥ 37.5°C axilla, ≥ 38.0°C oral), unsolicited AEs (days 0-29) and serious AEs (SAEs) and new-onset chronic illnesses (NOCIs; to day 180 after last vaccination).

RESULTS

At least one solicited AE was reported by 80%/78%/78% of children in Cohorts A, B and C, respectively. Systemic AEs were more common among Cohort A (72% of participants), and local AEs were more common among Cohort C (71% of participants). Fever was more common in younger cohorts, in influenza vaccine-naïve children (29% of Cohort A receiving their first dose), and following first compared with second doses. Severe fever following a first dose prevented 20 participants receiving their second scheduled vaccine dose. A 7-month-old participant had a single uncomplicated febrile convulsion on the day of vaccination.

CONCLUSIONS

Nearly 80% of subjects reported at least one solicited AE following immunization. Fever prevalence was highest in vaccine-naïve Cohort A participants, similar to other paediatric studies using CSL vaccine. Further research to understand fever-related AEs in children following CSL's TIV is recommended.

Clinical-Epidemiological Profile of Influenza A H1N1 Cases at a Tertiary Care Institute of India

Introduction:

Influenza virus is a common human pathogen that has caused serious respiratory illness and death over the past century. In April 2009, a new strain of Influenza virus A H1N1, commonly referred to as “swine flu”, began to spread in several countries around the world, and India confirmed its first case on 16 May 16 2009.

Aim:

To study the clinical and epidemiological profile of Influenza A H1N1 cases at the Government Medical College and Hospital, Chandigarh.

Materials and Methods:

Clinical epidemiological characteristics of Influenza A H1N1 cases from May 2009 to April 2010 were retrospectively, descriptively analyzed using data from the Influenza A H1N1 screening center and isolation ward at the Government Medical College and Hospital, Chandigarh. Data were Analyzed using MS Excel software.

Results:

At GMCH, till April 2010, a total of 4379 patients were screened for Influenza A H1N1, of which 365 patients were tested. The most common symptoms were fever (87.6%), cough (49.77%), sore throat (27%) and breathlessness (23.9%). The most common presentation (42.30%) of Influenza A H1N1 cases was fever and cold-like features, not cough. 29.58% (108) of the tested patients were found to be positive for the disease. Maximum cases were detected in the month of December, and the patients less than 40 years of age accounted for 81.4% (44 cases) of the cases. Influenza A H1N1 resulted in death of 54.9% (28) of the admitted cases, of which 46% (12) deaths occurred within 48 h of admission.

Conclusion:

On the basis of these findings, it can be safely hypothesized that prevalence of Influenza A H1N1 is high in the younger population, and fever, cough and sore throat are the most common symptoms with which the patients usually present.

Did socio-ecological factors drive the spatiotemporal patterns of pandemic influenza A (H1N1)?

BACKGROUND

Pandemic influenza A (H1N1) has a significant public health impact. This study aimed to examine the effect of socio-ecological factors on the transmission of H1N1 in Brisbane, Australia.

METHODOLOGY

We obtained data from Queensland Health on numbers of laboratory-confirmed daily H1N1 in Brisbane by statistical local areas (SLA) in 2009. Data on weather and socio-economic index were obtained from the Australian Bureau of Meteorology and the Australian Bureau of Statistics, respectively. A Bayesian spatial conditional autoregressive (CAR) model was used to quantify the relationship between variation of H1N1 and independent factors and to determine its spatiotemporal patterns.

RESULTS

Our results show that average increase in weekly H1N1 cases were 45.04% (95% credible interval (CrI): 42.63-47.43%) and 23.20% (95% CrI: 16.10-32.67%), for a 1 °C decrease in average weekly maximum temperature at a lag of one week and a 10mm decrease in average weekly rainfall at a lag of one week, respectively. An interactive effect between temperature and rainfall on H1N1 incidence was found (changes: 0.71%; 95% CrI: 0.48-0.98%). The auto-regression term was significantly associated with H1N1 transmission (changes: 2.5%; 95% CrI: 1.39-3.72). No significant association between socio-economic indexes for areas (SEIFA) and H1N1 was observed at SLA level.

CONCLUSIONS

Our results demonstrate that average weekly temperature at lag of one week and rainfall at lag of one week were substantially associated with H1N1 incidence at a SLA level. The ecological factors seemed to have played an important role in H1N1 transmission cycles in Brisbane, Australia.

Awareness, anxiety, compliance: community perceptions and response to the threat and reality of an influenza pandemic

This study compared community response prior to and during the H1N1 2009 influenza pandemic using a cross-sectional phone survey of rural and metropolitan South Australia, conducted in 2007 and 2009. Awareness of pandemic influenza was significantly higher and anxiety lower in 2009 than in 2007. Reported seasonal influenza vaccine uptake increased from 51.7% in 2007 to 61.4% in 2009, but there was more interest in receiving pandemic vaccine in 2007 (87.5%) than in 2009 (57%).

Differential effects of pandemic (H1N1) 2009 on remote and indigenous groups, Northern Territory, Australia, 2009

TOC summary: Vaccination campaigns and public health responses should focus on high-risk groups.

Pandemic (H1N1) 2009 influenza spread through the Northern Territory, Australia, during June–August 2009. We performed 2 cross-sectional serologic surveys on specimens from Northern Territory residents, with 445 specimens obtained prepandemic and 1,689 specimens postpandemic. Antibody titers were determined by hemagglutination inhibition against reference virus A/California/7/2009 on serum samples collected opportunistically from outpatients. All specimens had data for patients’ gender, age, and address, with patients’ indigenous status determined for 94.1%. Protective immunity (titer >40) was present in 7.6% (95% confidence interval [CI] 5.2%–10.1%) of prepandemic specimens and 19.5% (95% CI 17.6%–21.4%) of postpandemic specimens, giving a population-standardized attack rate of 14.9% (95% CI 11.0%–18.9%). Prepandemic proportion of immune persons was greater with increasing age but did not differ by other demographic characteristics. Postpandemic proportion of immune persons was greater in younger groups and around double in indigenous persons. Postpandemic proportion immune was geographically heterogeneous, particularly among remote-living and indigenous groups.

Transmission of influenza on international flights, may 2009

Understanding the dynamics of influenza transmission on international flights is necessary for prioritizing public health response to pandemic incursions. A retrospective cohort study to ascertain in-flight transmission of pandemic (H1N1) 2009 and influenza-like illness (ILI) was undertaken for 2 long-haul flights entering Australia during May 2009. Combined results, including survey responses from 319 (43%) of 738 passengers, showed that 13 (2%) had an ILI in flight and an ILI developed in 32 (5%) passengers during the first week post arrival. Passengers were at 3.6% increased risk of contracting pandemic (H1N1) 2009 if they sat in the same row as or within 2 rows of persons who were symptomatic preflight. A closer exposed zone (2 seats in front, 2 seats behind, and 2 seats either side) increased the risk for postflight disease to 7.7%. Efficiency of contact tracing without compromising the effectiveness of the public health intervention might be improved by limiting the exposed zone.

Influenza: One Health in action

Influenza highlights the relevance of One Health, where experts in animal, human and environmental health combine to solve inter-related problems. Human disease due to pandemic (H1N1) 2009 influenza and avian and human disease due to influenza A/H5N1 are recent examples of new zoonoses with significant global impact. Management and prevention of influenza and other emerging infectious diseases requires the expansion and continuing support of collaborations between human and animal health experts at the clinical, diagnostic laboratory, public health, research and training levels.

Epidemiologic modeling with FluSurge for pandemic (H1N1) 2009 outbreak, Queensland, Australia

At the beginning of the pandemic (H1N1) 2009 outbreak, we estimated the potential surge in demand for hospital-based services in 4 Health Service Districts of Queensland, Australia, using the FluSurge model. Modifications to the model were made on the basis of emergent evidence and results provided to local hospitals to inform resource planning for the forthcoming pandemic. To evaluate the fit of the model, a comparison between the model's predictions and actual hospitalizations was made. In early 2010, a Web-based survey was undertaken to evaluate the model's usefulness. Predictions based on modified assumptions arising from the new pandemic gained better fit than results from the default model. The survey identified that the modeling support was helpful and useful to service planning for local hospitals. Our research illustrates an integrated framework involving post hoc comparison and evaluation for implementing epidemiologic modeling in response to a public health emergency.

Surveillance of hospitalizations with pandemic A(H1N1) 2009 influenza infection in Queensland, Australia

OBJECTIVE

To describe the demographic and clinical characteristics of patients hospitalized with pandemic A(H1N1) 2009 infection in Queensland, Australia between 25 May and 3 October 2009 and to examine the relationship between timing of antiviral treatment and severity of illness.

METHOD

Using data from the Queensland Health EpiLog information system, descriptive analysis and logistic regression modelling were used to describe and model factors which influence patient outcomes (death, admission to intensive care unit and/or special care unit). Data on patients admitted to hospital in Queensland with confirmed pandemic A(H1N1) 2009 infection were included in this analysis.

RESULTS

1236 patients with pandemic A(H1N1) 2009 infection were admitted to hospitals in Queensland during the study period. Of the total group: 15% were admitted to an intensive care unit or special care unit; 3% died; 34% were under the age of 18 years and 8% were 65 years of age or older; and 55% had at least one underlying medical condition. Among the 842 patients for whom data were available regarding the use of antiviral drugs, antiviral treatment was initiated in 737 (87.5%) patients, treatment commenced at a median of one day (range 1-33 days) after onset of illness. Admission to an intensive care unit or special care unit (ICU/SCU) or death was significantly associated with increased age, lack of timeliness of antiviral treatment, chronic renal disease and morbid obesity.

DISCUSSION

Early antiviral treatment was significantly associated with lower likelihood of ICU/SCU admission or death. Early antiviral treatment for influenza cases may therefore have important public health implications.

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.

Responses to pandemic (H1N1) 2009, Australia

Perception of risk affects compliance with public health control measures.

In 2007, adults in Australia were interviewed about their willingness to comply with potential health interventions during a hypothetical influenza outbreak. After the first wave of pandemic (H1N1) 2009 in Australia, many of the same respondents were interviewed about behavior and protection measures they actually adopted. Of the original 1,155 respondents, follow-up interviews were conducted for 830 (71.9%). Overall, 20.4% of respondents in 2009 had recently experienced influenza-like illness, 77.7% perceived pandemic (H1N1) 2009 to be mild, and 77.8% reported low anxiety. Only 14.5% could correctly answer 4 questions about influenza virus transmission, symptoms, and infection control. Some reported increasing handwashing (46.6%) and covering coughs and sneezes (27.8%) to reduce transmission. Compared with intentions reported in 2007, stated compliance with quarantine or isolation measures in 2009 remained high. However, only respondents who perceived pandemic (H1N1) 2009 as serious or who had attained higher educational levels expressed intention to comply with social distancing measures.

Influenza A/H1N1_09: Australia and New Zealand's winter of discontent

Influenza A/H1N1_09 emerged in Mexico at the end of the Northern Hemisphere winter. Within weeks, the focus shifted to the Southern Hemisphere as the introduction of the novel virus coincided with the beginning of the influenza season. Intensive public health and health services planning had occurred in Australia and New Zealand as preparation for an influenza pandemic before 2009. However, this first pandemic wave was quite different to what had been expected. Key elements of the pandemic and response are outlined from the perspective of clinicians working at the frontline of patient care. In particular, they examine why past influenza pandemics and recent history are poor predictors of the current pandemic, the discordance between potential for transmission and disease severity, the broad clinical spectrum of H1N1_09 infection, clinical and health service management issues, and the relationship between health care and government policy. Finally, they address the need for the respiratory community to show leadership in times of crisis. Lessons learned in Australia and New Zealand during 2009 have important messages for similarly resourced countries in the Northern Hemisphere in the coming months as they face their own influenza season.