Absence of cross-reactive antibodies to influenza A (H1N1) 2009 before and after vaccination with 2009 Southern Hemisphere seasonal trivalent influenza vaccine in children aged 6 months-9 years: a prospective study

Please cite this paper as: McVernon et al. (2010) Absence of cross‐reactive antibodies to influenza A (H1N1) 2009 before and after vaccination with 2009 Southern Hemisphere seasonal trivalent influenza vaccine in children aged 6 months–9 years: a prospective study. Influenza and Other Respiratory Viruses 5(1), 7–11. Background Early outbreaks of the pandemic influenza A (H1N1) 2009 virus predominantly involved young children, who fuelled transmission through spread in homes and schools. Seroprevalence studies conducted on stored serum collections indicated low levels of antibody to the novel strain in this age group, leading many to recommend priority immunisation of paediatric populations. Objectives In a prospective study, we sought evidence of cross‐reactive antibodies to the pandemic virus in children who were naïve to seasonal influenza vaccines, at baseline and following two doses of the 2009 Southern Hemisphere trivalent influenza vaccine (TIV). Patients/Methods Twenty children were recruited, with a median age of 4 years (interquartile range 3–5 years); all received two age appropriate doses of TIV. Paired sera were collected pre‐ and post‐vaccination for the assessment of vaccine immunogenicity, using haemagglutination inhibition and microneutralisation assays against vaccine‐related viruses and influenza A (H1N1) 2009. Results Robust responses to H3N2 were observed regardless of age or pre‐vaccination titre, with 100% seroconversion. Fewer seroconverted to the seasonal H1N1 component. Only two children were weakly seropositive (HI titre 40) to the pandemic H1N1 strain at study entry, and none showed evidence of seroconversion by HI assay following TIV administration. Conclusions Administration of 2009 Southern Hemisphere TIV did little to elicit cross‐reactive antibodies to the pandemic H1N1 virus in children, in keeping with assay results on stored sera from studies of previous seasonal vaccines. Our findings support the recommendations for influenza A (H1N1) 2009 vaccination of children in preparation for the 2010 winter season.     

Seroprevalence of pandemic (H1N1) 2009 influenza and effectiveness of 2010/2011 influenza vaccine during 2010/2011 season in Beijing, China

Please cite this paper as: Yang et al. (2011) Seroprevalence of pandemic (H1N1) 2009 influenza and effectiveness of 2010/2011 influenza vaccine during 2010/2011 season in Beijing, China. Influenza and Other Respiratory Viruses 6(6), 381–388. Background In the post‐pandemic period, pandemic (H1N1) 2009 virus was expected to circulate seasonally and was introduced into trivalent influenza vaccine during 2010/2011 season in the Northern Hemisphere. Objectives The aim of this study was to examine the evolution of herd immunity against pandemic (H1N1) 2009 virus in Beijing, China, during 2010/2011 season and effectiveness of the 2010/2011 trivalent vaccine. Methods Two serological surveys were conducted before and after 2010/2011 season in Beijing. A case–control study was used to investigate vaccine effectiveness against influenza‐like illness (ILI) and lower respiratory tract infection (LRI). Results A total of 4509 and 4543 subjects participated in the pre‐ and post‐season surveys, respectively. The standardized seroprevalence of pandemic (H1N1) 2009 influenza increased from 22·1% pre‐season to 24·3% post‐season (P < 0·001). Significant elevation in seroprevalence appeared in the ≥60 years age‐group (P < 0·001), but not in others. The 2010/2011 trivalent vaccine contributed to the higher post‐seasonal seroprevalence in unvaccinated individuals (P = 0·024), but not in those vaccinated with monovalent pandemic vaccine (P = 0·205), as well as in those without prior immunity versus those with immunity. The adjusted effectiveness of the 2010/2011 trivalent vaccine was 79% protection against ILI (95% CI, 61–89%) and 95% against LRI (95% CI: 59–99%). Conclusions A slight increase in herd immunity against pandemic (H1N1) 2009 influenza was observed in Beijing, China, during the 2010/2011 season. Prior vaccination and immunity had a suppressive impact on immune response toward this novel influenza virus, elicited by 2010/2011 trivalent vaccine. This trivalent vaccine conferred good protection against ILI and LRI.     

Cumulative incidence of pandemic influenza A (H1N1) 2009 by a community-based serological cohort study in Selenghe Province, Mongolia

Please cite this paper as: Burmaa et al. (2012) Cumulative incidence of pandemic influenza A (H1N1) 2009 by a community‐based serological cohort study in Selenghe Province, Mongolia. Influenza and Other Respiratory Viruses 6(601), e97–e104. Background Large community outbreaks of pandemic A (H1N1) 2009 occurred between October and December 2009 in Mongolia. A serological study was conducted among the general population by testing paired sera collected before and after the first wave of pandemic in Selenghe province, Mongolia. None of the study participants had been vaccinated for pandemic A (H1N1) 2009 before the second samples were collected. Objective The objective of this study was to estimate cumulative incidence of pandemic A (H1N1) 2009 in different age‐groups of Selenghe province residents. Methods After informed consent was obtained from apparently healthy volunteers, the paired sera and background information were collected. Antibody titers were measured using hemagglutinin inhibition (HI) and microneutralization (MN) assays for A/California/07/2009pdm. A fourfold rise in antibody titers was regarded as the evidence of infection. Results The overall cumulative incidences in the study group for all ages were 28·8% (76/264) by HI, 35·2% (93/264) by MN, and 25·0% (66/264) by both HI and MN. Cumulative incidences of infection varied among age‐groups, with children aged 2–4 and 5–9 years having high cumulative incidence of infection. Overall cumulative incidences of infection in the whole population were estimated to be 23·0% (4946/21 460) by HI, 30·2% (6473/21 460) by MN, and 18·8% (4036/21 460) by both HI and MN. Conclusions This study indicates that about one‐fourth of the total population in Selenghe province was infected with pandemic A (H1N1) 2009 virus during the first wave of the pandemic.     

Clinical, laboratory and radiologic characteristics of 2009 pandemic influenza A/H1N1 pneumonia: primary influenza pneumonia versus concomitant/secondary bacterial pneumonia

Please cite this paper as: Song et al. (2011). Clinical, laboratory and radiologic characteristics of 2009 pandemic influenza A/H1N1 pneumonia: primary influenza pneumonia versus concomitant/secondary bacterial pneumonia. Influenza and Other Respiratory Viruses 5(6), e535–e543. Background Although influenza virus usually involves the upper respiratory tract, pneumonia was seen more frequently with the 2009 pandemic influenza A/H1N1 than with seasonal influenza. Methods From September 1, 2009, to January 31, 2010, a specialized clinic for patients (aged ≥15 years) with ILI was operated in Korea University Guro Hospital. RT‐PCR assay was performed to diagnose 2009 pandemic influenza A/H1N1. A retrospective case–case–control study was performed to determine the predictive factors for influenza pneumonia and to discriminate concomitant/secondary bacterial pneumonia from primary influenza pneumonia during the 2009–2010 pandemic. Results During the study period, the proportions of fatal cases and pneumonia development were 0·12% and 1·59%, respectively. Patients with pneumonic influenza were less likely to have nasal symptoms and extra‐pulmonary symptoms (myalgia, headache, and diarrhea) compared to patients with non‐pneumonic influenza. Crackle was audible in just about half of the patients with pneumonic influenza (38·5% of patients with primary influenza pneumonia and 53·3% of patients with concomitant/secondary bacterial pneumonia). Procalcitonin, C‐reactive protein (CRP), and lactate dehydrogenase were markedly increased in patients with influenza pneumonia. Furthermore, procalcitonin (cutoff value 0·35 ng/ml, sensitivity 81·8%, and specificity 66·7%) and CRP (cutoff value 86·5 mg/IU, sensitivity 81·8%, and specificity 59·3%) were discriminative between patients with concomitant/secondary bacterial pneumonia and patients with primary influenza pneumonia. Conclusions Considering the subtle manifestations of 2009 pandemic influenza A/H1N1 pneumonia in the early stage, high clinical suspicion is required to detect this condition. Both procalcitonin and CRP would be helpful to differentiate primary influenza pneumonia from concomitant/secondary bacterial pneumonia.     

Epidemiologic and virologic assessment of the 2009 influenza A (H1N1) pandemic on selected temperate countries in the Southern Hemisphere: Argentina, Australia, Chile, New Zealand and South Africa

Please cite this paper as: Van Kerkhove et al. (2011) Epidemiologic and virologic assessment of the 2009 influenza A (H1N1) pandemic on selected temperate countries in the Southern Hemisphere: Argentina, Australia, Chile, New Zealand and South Africa. Influenza and Other Respiratory Viruses 5(6), e487–e498. 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.     

A novel electrochemical device to differentiate pandemic (H1N1) 2009 from seasonal influenza

Please cite this paper as: Straight et al. (2010) A novel electrochemical device to differentiate pandemic (H1N1) 2009 from seasonal influenza. Influenza and Other Respiratory Viruses 4(2), 73–79. Background One of the challenges of the recent pandemic (H1N1) 2009 influenza outbreak was to differentiate the virus from seasonal influenza when confronting clinical cases. The determination of the virus has implications on treatment choice, and obvious epidemiologic significance. Objectives We set out to apply a novel electrochemical device to samples derived from clinical cases of pandemic (H1N1) 2009 influenza to examine the ability of the device to differentiate these samples from cases of seasonal influenza. Patients/Methods An IRB approved protocol allowed for the use of original nasal wash samples from 24 confirmed human cases pandemic (H1N1) 2009 influenza. Clinical samples from cases of seasonal influenza (Influenza A/H1N1, A/H3N2, and B) were included as controls. Nucleic acids were extracted and samples examined by the ElectraSense^® Influenza A assay (CombiMatrix, Inc). Samples were also examined by RT-PCR or Luminex assays as a comparator. Results and Conclusions The ElectraSense^® Influenza A assay correctly identified 23 of 24 samples of laboratory-confirmed pandemic (H1N1) 2009 Influenza. The assay correctly identified all samples of influenza A/H1N1 and A/H3N2, and differentiated these from pandemic (H1N1) 2009 Influenza in all cases. The ElectraSense^® Influenza A assay proved to be a useful assay to quickly and accurately differentiate pandemic (H1N1) 2009 influenza from seasonal influenza.     

Attempted early detection of influenza A (H1N1) pandemic with surveillance data of influenza-like illness and unexplained pneumonia

Please cite this paper as: Qian et al. (2011) Attempted early detection of influenza A (H1N1) pandemic with surveillance data of influenza‐like illness and unexplained pneumonia. Influenza and Other Respiratory Viruses 5(6), e479–e486. Background To collect disease information and provide data for early detection of epidemics, two surveillance systems were established for influenza‐like illness (ILI) and unexplained pneumonia (UP) in Wuxi, People’s Republic of China. Objectives The current study aims to describe the performance of these surveillance systems during 2004–2009 and to evaluate the value of surveillance data in detection of influenza epidemics. Methods Two national ILI sentinel hospitals and three UP sentinel hospitals provided data to the surveillance systems. The surveillance data from hospital‐based outpatient clinics and emergency rooms were compared by year. The ILI data of 2009 were further modeled based on previous data using both a control chart method and a moving average regression method. Alarms of potential epidemics would be raised when the input surveillance data surpassed a threshold. Results In 2009, the proportions of ILI and respiratory illness with fever (one surveillance syndrome of the UP system) to total patient visits (3·40% and 11·76%, respectively) were higher than the previous years. The surveillance data of both systems also showed developing trends similar to the influenza A (H1N1) pandemic in 2009. When the surveillance data of 2009 were fitted in the two detection models, alarms were produced on the occurrence of the first local case of influenza A (H1N1), outbreaks in schools and in general populations. Conclusions The results indicated the potential for using ILI and UP surveillance data as syndromic indicators to detect and provide an early warning for influenza epidemics.     

Mortality attributable to pandemic influenza A (H1N1) 2009 in San Luis Potosí, Mexico

Please cite this paper as: Comas‐García et al. (2011) Mortality attributable to pandemic influenza A (H1N1) 2009 in San Luis Potosí, Mexico. Influenza and Other Respiratory Viruses 5(2), 76–82. Background Acute respiratory infections are a leading cause of morbidity and mortality worldwide. Starting in 2009, pandemic influenza A(H1N1) 2009 virus has become one of the leading respiratory pathogens worldwide. However, the overall impact of this virus as a cause of mortality has not been clearly defined. Objectives To determine the impact of pandemic influenza A(H1N1) 2009 on mortality in a Mexican population. Methods We assessed the impact of pandemic influenza virus on mortality during the first and second outbreaks in San Luis Potosí, Mexico, and compared it to mortality associated with seasonal influenza and respiratory syncytial virus (RSV) during the previous winter seasons. Results We estimated that, on average, 8·1% of all deaths that occurred during the 2003–2009 seasons were attributable to influenza and RSV. During the first pandemic influenza A(H1N1) 2009 outbreak, there was an increase in mortality in persons 5–59 years of age, but not during the second outbreak (Fall of 2009). Overall, pandemic influenza A (H1N1) 2009 outbreaks had similar effects on mortality to those associated with seasonal influenza virus epidemics. Conclusions The impact of influenza A(H1N1) 2009 virus on mortality during the first year of the pandemic was similar to that observed for seasonal influenza. The establishment of real‐time surveillance systems capable of integrating virological, morbidity, and mortality data may result in the timely identification of outbreaks so as to allow for the institution of appropriate control measures to reduce the impact of emerging pathogens on the population.     

Antibody responses against influenza A(H1N1)pdm09 virus after sequential vaccination with pandemic and seasonal influenza vaccines in Finnish healthcare professionals

Background Influenza A(H1N1)pdm09 virus has been circulating in human population for three epidemic seasons. During this time, monovalent pandemic and trivalent seasonal influenza vaccination against this virus have been offered to Finnish healthcare professionals. It is, however, unclear how well vaccine‐induced antibodies recognize different strains of influenza A(H1N1)pdm09 circulating in the population and whether the booster vaccination with seasonal influenza vaccine would broaden the antibody cross‐reactivity. Objectives Influenza vaccine‐induced humoral immunity against several isolates of influenza A(H1N1)pdm09 virus was analyzed in healthcare professionals. Age‐dependent responses were also analyzed. Methods Influenza viruses were selected to represent viruses that circulated in Finland during two consecutive influenza epidemic seasons 2009–2010 and 2010–2011. Serum samples from vaccinated volunteers, age 20–64 years, were collected before and after vaccination with AS03‐adjuvanted pandemic and non‐adjuvanted trivalent seasonal influenza vaccine that was given 1 year later. Results Single dose of pandemic vaccine induced a good albeit variable antibody response. On day 21 after vaccination, depending on the virus strain, 14–75% of vaccinated had reached antibody titers (≥1:40) considered seroprotective. The booster vaccination 1 year later with a seasonal vaccine elevated the seroprotection rate to 57–98%. After primary immunization, younger individuals (20–48 years) had significantly higher antibody titers against all tested viruses than older persons (49–64 years) but this difference disappeared after the seasonal booster vaccination. Conclusions Even a few amino acid changes in influenza A HA may compromise the vaccine‐induced antibody recognition. Older adults (49 years and older) may benefit more from repeated influenza vaccinations.     

Online monitoring of flu in Belgium

Please cite this paper as: Devroey et al. (2011) Online monitoring of flu in Belgium. Influenza and Other Respiratory Viruses 5(5), 351–356. Background The diagnosis and treatment of patients with the A(H1N1) pandemic flu caused some serious burden for general practitioners (GPs) in the summer and autumn of 2009. Objective The aim of this study was to track the incidence of influenza and influenza‐like illness (ILI) in Belgium and to describe the characteristics of the affected patients. Methods In July 2009, the Belgian online influenza surveillance system (BOISS) was set up to monitor the spread of influenza and ILI. Registrations were made by 93 GPs from all 10 Belgian provinces who participated at least 1 week during the first 12 months of the registration. Only patients who met the WHO criteria for flu were recorded. Results In total, 1254 patients (53% men) with influenza or ILI were included. Mainly younger persons were affected: 43% was under the age of 20 years. A risk factor for influenza‐related complications was determined in 19% of cases, mainly patients with chronic respiratory problems. A treatment with oseltamivir or zanamivir was prescribed in 13%, and 3% of the patients was admitted to a hospital. The time of the peak incidence (44th week) and the magnitude (623 cases per week per 100 000 inhabitants) corresponded with the figures of the existing paper‐based registration network. The small sample size and possible reporting biases may have influenced the findings of the study. Conclusions The BOISS provides a good alternative to conduct surveillance activities for influenza and ILI in Belgium. It provides complementary information regarding ILI compared to the existing data capturing.     

Transmission dynamics and risk factors for pandemic H1N1-related illness: outbreak investigation in a rural community of British Columbia, Canada

Please cite this paper as: Janjua et al. (2012) Transmission dynamics and risk factors for pandemic H1N1‐related illness: outbreak investigation in a rural community of British Columbia, Canada. Influenza and Other Respiratory Viruses 6(3), e54–e62. Objective To characterize the first‐wave epidemiologic features of influenza‐like illness (ILI) associated with the novel pandemic A/H1N1 [A(H1N1)pdm09] virus. Methods We used generalized linear mixed models (GLMM) to assess risk factors and non‐parametric and/or parametric distributions to estimate attack rates, secondary attack rates (SAR), duration of illness, and serial interval during a laboratory‐confirmed community outbreak of A(H1N1)pdm09 clustered around on‐reserve residents and households of an elementary school in rural British Columbia, Canada, in late April/early May 2009. ILI details were collected as part of outbreak investigation by community telephone survey in early June 2009. Results Overall, 92/408 (23%) of participants developed ILI and 36/408 (9%) experienced medically attended ILI (MAILI). The overall SAR in households was 22%: highest among participants 1–4 years of age (yoa) (50%) followed by <1 yoa (38%), 5–8 yoa (20%), 10–19 yoa (13%), 20–49 yoa (20%), and 50–64 yoa (0%). The median serial interval was estimated at 3·5 days (95% CI: 2·1–5·1). In multivariable GLMM analysis, having a chronic condition (OR: 2·58; 95% CI: 1·1–6·04), younger age [1–8 yoa: OR: 4·63; 95% CI: 2·25–9·52; 9–19 yoa: OR: 1·95; 95% CI: 0·97–3·9 (referent: ≥20 yoa)] and receipt of 2008–2009 influenza vaccine (OR: 2·68; 95% CI: 1·37–5·25) were associated with increased risk of ILI. Median duration of illness was 9 days, longer among those with chronic conditions (21 days). Median time to seeking care after developing illness was 4·5 days. On‐reserve participants had higher chronic conditions, household density, ILI, MAILI, and SAR. Conclusions During a community outbreak of A(H1N1)pdm09‐related illness, we identified substantial clinical ILI attack rates exceeding 20% with secondary household attack rates as high as 50% in young children. The serial interval was short suggesting a narrow period to prevent transmission.     

Epidemiological and clinical features of respiratory viral infections in hospitalized children during the circulation of influenza virus A(H1N1) 2009

Please cite this paper as: Zuccotti et al. (2011) Epidemiological and clinical features of respiratory viral infections in hospitalized children during the circulation of influenza virus A(H1N1) 2009. Influenza and Other Respiratory Viruses 5(6), e528–e534. Background Seasonal influenza viruses and respiratory syncytial virus (RSV) are primary causes of acute respiratory tract infections (ARTIs) in children. New respiratory viruses including human metapneumovirus (hMPV), human bocavirus (hBoV), and influenza 2009 A(H1N1) virus have a strong impact on the pediatric population. Objectives To evaluate epidemiological and clinical features of ARTIs in hospitalized children. Methods From December 1, 2008, to December 31, 2009, all children under age fifteen (n = 575) hospitalized for ARTIs were investigated for influenza A (subtype H1N1, H3N2, and 2009 H1N1) and B, RSV A and B, hMPV, and hBoV by PCR. Results Fifty‐one percent of samples were positive for these respiratory viruses. The frequencies of virus detection were RSV 34·1%, hBoV 6·8%, hMPV 5%, seasonal influenza A 5%, and seasonal influenza B 0%. From April 2009, 11·6% of collected samples were influenza 2009 A(H1N1) positive. Respiratory syncytial virus activity peaked in January, hBoV in February, and hMPV in April. Seasonal influenza A was detected only between January and April 2009, while influenza 2009 A(H1N1) peaked in November. Respiratory syncytial virus and hMPV were mainly associated with lower respiratory tract infections (LRTIs) and with necessity of O₂ administration. The 2009 pandemic influenza was more frequently detected in elder children (P < 0·001) and was associated with higher, longer‐lasting fevers compared with other viral infections (P < 0·05). Conclusions All considered viruses were involved in LRTIs. The primary clinical relevance of RSV and a similar involvement of both seasonal influenza and emerging viruses investigated were observed on the pediatric population.     

Influenza-associated bacterial pathogens in patients with 2009 influenza A (H1N1) infection: impact of community-associated methicillin-resistant Staphylococcus aureus in Queensland, Australia

Background: Secondary bacterial pneumonia due to community onset methicillin‐resistant Staphylococcus aureus (MRSA) has become a highly publicised cause of influenza‐associated death. There is a risk that case reports of fatal outcomes with post‐influenza MRSA pneumonia may unduly influence antibiotic prescribing. Aims: The aim of this study was to demonstrate the incidence of community‐onset MRSA pneumonia in 2009 H1N1 influenza patients. Methods: The microbiology records of patients positive for influenza A (H1N1) in 2009 were reviewed for positive blood or respiratory tract cultures and urinary pneumococcal antigen results within a Queensland database. Patients with such positive results within 48 h of hospital admission and a positive H1N1 influenza result in the prior 6 weeks were included. Results: In 2009, 4491 laboratory‐confirmed pandemic influenza A (H1N1) infections were detected. Fifty patients (1.1% of the H1N1 cohort) who were hospitalised with H1N1 and who had a bacterial respiratory tract pathogen were identified. Streptococcus pneumoniae (16 patients; 32%), Staphylococcus aureus (13 patients; 26%) and Haemophilus influenzae (9 patients; 18%) were the most commonly cultured organisms. Of the cohort of 4491 patients, MRSA was detected in only two patients, both of whom were admitted to intensive care units and survived after prolonged admissions. Conclusions: Influenza‐associated community‐onset MRSA pneumonia was infrequently identified in the 2009 H1N1 season in Queensland, despite community‐onset MRSA skin and soft tissue infections being very common. Although post‐influenza MRSA pneumonia is of great concern, its influence on empiric‐prescribing guidelines should take into account its incidence relative to other secondary bacterial pathogens.     

H1N1 swine origin influenza infection in the United States and Europe in 2009 may be similar to H1N1 seasonal influenza infection in two Australian states in 2007 and 2008

Background The population‐based impact of infection with swine origin influenza A (H1N1) virus infection was not clear in the early days of the epidemic towards the end of May 2009. Australia had seven confirmed cases by 22 May 2009. We aimed to compare available data on swine origin influenza A (H1N1) virus infection overseas with seasonal influenza A (H1N1) virus infection in Australia to assist with forward planning. Methods Data on infection with seasonal influenza A (H1N1) virus in patients recruited through sentinel general practices in Victoria and Western Australia in 2007 and 2008 were compared with early publications on infection with swine origin influenza A (H1N1) virus in the United States and Europe. Results Influenza A (H1N1) virus infection was predominantly a disease of younger people, regardless of whether the virus was of swine or human origin. The median age of infection with swine origin virus was 20 years in the United States and 22 years in Spain, while the median age of infection with human origin virus was 18 years in Western Australia and 23 years in Victoria. Conclusions The median age of infection with influenza A (H1N1) virus was around 20 ± 3 years, independent of the origin of the H1N1 virus but a higher proportion of swine origin influenza infections occurred in people aged 10–18 years. This is at least partially explained by biased sampling among surveillance patients, although it may also reflect a different infection pattern.     

Surveillance of Influenza in Indonesia, 2003–2007

Background Longitudinal data are limited about the circulating strains of influenza viruses and their public health impact in Indonesia. We conducted influenza surveillance among outpatients and hospitalized patients with influenza‐like illness (ILI) across the Indonesian archipelago from 2003 through 2007. Methodology Demographic, clinical data, and respiratory specimens were collected for 4236 ILI patients tested for influenza virus infection by RT‐PCR and viral culture. Principal Findings Influenza A and B viruses co‐circulated year‐round with seasonal peaks in influenza A virus activity during the rainy season (December–January). During 2003–2007, influenza viruses were identified in 20·1% (4236/21 030) of ILI patients, including 20·1% (4015/20 012) of outpatients, and 21·7% (221/1018) of inpatients. One H5N1 case was identified retrospectively in an outpatient with ILI. Antigenic drift in circulating influenza A and B virus strains was detected during the surveillance period in Indonesia. In a few instances, antigenically drifted viruses similar to the World Health Organization (WHO) vaccine strains were detected earlier than the date of their designation by WHO. Conclusions Influenza A and B virus infections are an important cause of influenza‐like illness among outpatients and hospitalized patients in Indonesia. While year‐round circulation of influenza viruses occurs, prevention and control strategies should be focused upon the seasonal peak during rainy season months. Ongoing virologic surveillance and influenza disease burden studies in Indonesia are important priorities to better understand the public health impact of influenza in South‐East Asia and the implications of influenza viral evolution and global spread.     

2009 pandemic Influenza A (H1N1): clinical and laboratory characteristics in pediatric and adult patients and in patients with pulmonary involvement

Please cite this paper as: Lee and Liu et al. (2012) 2009 pandemic Influenza A (H1N1): clinical and laboratory characteristics in pediatric and adult patients and in patients with pulmonary involvement. Influenza and Other Respiratory Viruses 6(601), e152–e161. Background To better understand clinical and laboratory characteristics in children, adults, and patients with lung involvement suffering 2009 pandemic influenza A (H1N1). Methods A total of 442 patients with 2009 pandemic influenza A (H1N1) were retrospectively analyzed. Results Comparing to their adult counterpart (n = 55), pediatric patients (n = 387) had significantly higher frequencies of fever, rhinorrhea, cough, sore throat, nausea/vomiting, and longer length of fever; lower frequencies of chest pain and dyspnea; higher incidence of lymphopenia; and lower incidence of elevated serum C‐reactive protein. Among the 227 patients with radiographs available, lung involvement was found in 19 (8·4%) (52·6% consolidation and 47·4% interstitial infiltrations), including 18 children and one adult. One child with lung consolidation died of multiorgan failure. Significant findings in patients with lung involvement included predominant young age (≤10 years), prolonged fever, and delayed oseltamivir therapy (≥48 hours after onset of illness); higher frequencies of dyspnea, nausea/vomiting, and altered consciousness; and higher incidences of leukopenia, elevated serum creative kinase, and lactic dehydrogenase. Conclusions Among patients with 2009 pandemic influenza A (H1N1), we found significant difference in clinical manifestations between children and adults, and significant differences in clinical and laboratory manifestations between patients with lung involvement and those without. On the basis of data from this study and the existing literature, early treatment with oseltamivir is recommended for patients with 2009 pandemic influenza A (H1N1), regardless of age.