[Show abstract][Hide abstract] ABSTRACT: Since the start of the 2009 influenza A pandemic (H1N1pdm), the World Health Organization and its member states have gathered information to characterize the clinical severity of H1N1pdm infection and to assist policy makers to determine risk groups for targeted control measures.
Data were collected on approximately 70,000 laboratory-confirmed hospitalized H1N1pdm patients, 9,700 patients admitted to intensive care units (ICUs), and 2,500 deaths reported between 1 April 2009 and 1 January 2010 from 19 countries or administrative regions--Argentina, Australia, Canada, Chile, China, France, Germany, Hong Kong SAR, Japan, Madagascar, Mexico, The Netherlands, New Zealand, Singapore, South Africa, Spain, Thailand, the United States, and the United Kingdom--to characterize and compare the distribution of risk factors among H1N1pdm patients at three levels of severity: hospitalizations, ICU admissions, and deaths. The median age of patients increased with severity of disease. The highest per capita risk of hospitalization was among patients <5 y and 5-14 y (relative risk [RR] = 3.3 and 3.2, respectively, compared to the general population), whereas the highest risk of death per capita was in the age groups 50-64 y and ≥65 y (RR = 1.5 and 1.6, respectively, compared to the general population). Similarly, the ratio of H1N1pdm deaths to hospitalizations increased with age and was the highest in the ≥65-y-old age group, indicating that while infection rates have been observed to be very low in the oldest age group, risk of death in those over the age of 64 y who became infected was higher than in younger groups. The proportion of H1N1pdm patients with one or more reported chronic conditions increased with severity (median = 31.1%, 52.3%, and 61.8% of hospitalized, ICU-admitted, and fatal H1N1pdm cases, respectively). With the exception of the risk factors asthma, pregnancy, and obesity, the proportion of patients with each risk factor increased with severity level. For all levels of severity, pregnant women in their third trimester consistently accounted for the majority of the total of pregnant women. Our findings suggest that morbid obesity might be a risk factor for ICU admission and fatal outcome (RR = 36.3).
Our results demonstrate that risk factors for severe H1N1pdm infection are similar to those for seasonal influenza, with some notable differences, such as younger age groups and obesity, and reinforce the need to identify and protect groups at highest risk of severe outcomes. Please see later in the article for the Editors' Summary.
PLoS Medicine 07/2011; 8(7):e1001053. DOI:10.1371/journal.pmed.1001053 · 14.43 Impact Factor
[Show abstract][Hide abstract] ABSTRACT: Introduction and Setting Our analysis compares the most comprehensive epidemiologic and virologic surveillance data compiled to date for laboratory-confirmed H1N1pdm patients between 1 April 2009 - 31 January 2010 from five temperate countries in the Southern Hemisphere-Argentina, Australia, Chile, New Zealand, and South Africa. Objective We evaluate transmission dynamics, indicators of severity, and describe the co-circulation of H1N1pdm with seasonal influenza viruses. Results In the five countries, H1N1pdm became the predominant influenza strain within weeks of initial detection. South Africa was unique, first experiencing a seasonal H3N2 wave, followed by a distinct H1N1pdm wave. Compared with the 2007 and 2008 influenza seasons, the peak of influenza-like illness (ILI) activity in four of the five countries was 3-6 times higher with peak ILI consultation rates ranging from 35/1,000 consultations/week in Australia to 275/100,000 population/week in New Zealand. Transmission was similar in all countries with the reproductive rate ranging from 1.2-1.6. The median age of patients in all countries increased with increasing severity of disease, 4-14% of all hospitalized cases required critical care, and 26-68% of fatal patients were reported to have ≥1 chronic medical condition. Compared with seasonal influenza, there was a notable downward shift in age among severe cases with the highest population-based hospitalization rates among children <5 years old. National population-based mortality rates ranged from 0.8-1.5/100,000. Conclusions The difficulty experienced in tracking the progress of the pandemic globally, estimating its severity early on, and comparing information across countries argues for improved routine surveillance and standardization of investigative approaches and data reporting methods.
Influenza and Other Respiratory Viruses 04/2011; 5(6):e487 - e498. DOI:10.1111/j.1750-2659.2011.00249.x · 2.20 Impact Factor
[Show abstract][Hide abstract] ABSTRACT: Assessment of the severity of disease due to the 2009 pandemic influenza A(H1N1) in Australian states and territories has been hampered by the absence of denominator data on population exposure. We compared antibody reactivity to the pandemic virus using haemagglutination inhibition assays performed on plasma specimens taken from healthy adult blood donors (older than 16 years) before and after the influenza pandemic that occurred during the southern hemisphere winter. Pre-influenza season samples (April – May 2009, n=496) were taken from donation collection centres in North Queensland (in Cairns and Townsville); post-outbreak specimens (October – November 2009, n=779) were from donors at seven centres in five states. Using a threshold antibody titre of 40 as a marker of recent infection, we observed an increase in the influenza-seropositive proportion of donors from 12% to 22%, not dissimilar to recent reports of influenza A(H1N1)-specific immunity in adults from the United Kingdom. No significant differences in seroprevalence were observed between Australian states, although the ability to detect minor variations was limited by the sample size. On the basis of these figures and national reporting data, we estimate that approximately 0.23% of all individuals in Australia exposed to the pandemic virus required hospitalisation and 0.01% died. The low seroprevalence reported here suggests that some degree of prior immunity to the virus, perhaps mediated by broadly reactive T-cell responses to conserved influenza viral antigens, limited transmission among adults and thus constrained the pandemic in Australia.
Eurosurveillance: bulletin europeen sur les maladies transmissibles = European communicable disease bulletin 10/2010; 15(40). · 5.72 Impact Factor
[Show abstract][Hide abstract] ABSTRACT: 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.
[Show abstract][Hide abstract] ABSTRACT: The 2008 influenza season was moderate overall, with fewer laboratory-confirmed cases and influenza-like illness (ILI) presentations than in 2007, which was the most severe influenza season since national reporting of influenza began in 2001. In 2008, the number of laboratory-confirmed notifications for influenza was 1.9 times higher than the 5-year mean. High notification rates were reflected in an increase in presentations with ILI to sentinel general practices and emergency departments. Notification rates were highest in the 0-4 year age group. Unusually, the season was predominantly due to influenza B, with 54% of notifications being influenza B and 43% being influenza A (3% type unknown). The rate of influenza B was higher among the younger age groups, compared with influenza A, which was more common in the older age groups. Of influenza viruses circulating during the 2008 season, A(H3) viruses were predominant and were antigenically similar to the 2008 A(H3) vaccine strain, while the majority of A(H1) strains showed significant drift away from the 2008 A(H1) vaccine strain. There were approximately equal proportions of viruses from the 2 influenza B lineages B/Yamagata and B/Victoria.
[Show abstract][Hide abstract] ABSTRACT: 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.
[Show abstract][Hide abstract] ABSTRACT: In 2006, 66 diseases and conditions were nationally notifiable in Australia. States and territories reported a total of 138,511 cases of communicable diseases to the National Notifiable Diseases Surveillance System: an increase of 10.4% on the number of notifications in 2005. In 2006, the most frequently notified diseases were sexually transmissible infections (57,941 notifications, 42% of total notifications), gastrointestinal diseases (27,931 notifications, 20% of total notifications) and vaccine preventable diseases (22,240 notifications, 16% of total notifications). There were 19,111 notifications of bloodborne diseases; 8,606 notifications of vectorborne diseases; 1,900 notifications of other bacterial infections; 767 notifications of zoonoses and 3 notifications of quarantinable diseases.
[Show abstract][Hide abstract] ABSTRACT: The year 2007 saw the most severe influenza season since national reporting of influenza began in 2001. Early in the season the National Incident Room was activated to provide effective national surveillance, reporting and management of the 2007 seasonal influenza outbreak. A surveillance team were tasked with establishing enhanced surveillance for the 2007 season and investigating unusual events in this outbreak. Key data required to comprehensively describe the number of cases, morbidity, mortality and virology of the influenza outbreak and the possible sources of these data were identified. In 2007 the number of laboratory-confirmed notifications for influenza was 3.1 times higher than the five-year mean. Forty-four per cent of notifications occurred in Queensland. High notification rates were reflected in an increase in presentations with influenza-like illness to sentinel general practices and Emergency Departments. Notifications and notification rates were highest in the 0-4 and 5-9 years age groups, possibly due to a bias towards testing in these age groups. The clinical morbidity of the infection in terms of complications or most affected groups cannot be determined but anecdotal reports indicate this season may have impacted young adults more than is usual. The available data suggest influenza has caused a significant burden on workplaces and the health care system as indicated by data on absenteeism and presentations for health care. The proportion of H1 strains of influenza circulating varied across Australia but was higher than 2006 in most jurisdictions. In 2007, 1,406 influenza isolates from Australia were antigenically analysed at the World Health Organization Collaborating Centre for Reference and Research on Influenza in Melbourne: 58.7% were A(H3N2), 34.4% were A(H1N1) and 6.9% were influenza B viruses. Antigenic drift away from the vaccine strain A/Wisconsin/67/2005 was observed with the A(H3N2) viruses and was also seen with most of the A(H1N1) viruses when compared with the vaccine strain A/New Caledonia/20/99. The small number of influenza B viruses examined were predominately of the B/Yamagata-lineage. Monitoring influenza through the National Incident Room during the 2007 season offered an excellent opportunity to conduct enhanced surveillance under conditions that were real and potentially serious but not an emergency. It enabled the current state of our surveillance systems to be assessed and opportunities for improvement to be identified.
[Show abstract][Hide abstract] ABSTRACT: In 2005, 60 diseases and conditions were nationally notifiable in Australia. States and territories reported a total of 125,461 cases of communicable diseases to the National Notifiable Diseases Surveillance System: an increase of 10% on the number of notifications in 2004. In 2005, the most frequently notified diseases were sexually transmissible infections (51,557 notifications, 41% of total notifications), gastrointestinal diseases (29,422 notifications, 23%) and bloodborne diseases (19,278 notifications, 15%). There were 17,753 notifications of vaccine preventable diseases; 4,935 notifications of vectorborne diseases; 1,826 notification of other bacterial infections (legionellosis, leprosy, meningococcal infections and tuberculosis) and 687 notifications of zoonotic diseases.