Population‐based surveillance for 2009 pandemic influenza A (H1N1) virus in Guatemala, 2009

Please cite this paper as: Reyes et al. (2010) Population‐based surveillance for 2009 pandemic influenza A (H1N1) virus in Guatemala, 2009. Influenza and Other Respiratory Viruses 4(3), 129–140. Background  In April 2009, 2009 pandemic influenza A H1N1 (2009 H1N1) was first identified in Mexico but did not cause widespread transmission in neighboring Guatemala until several weeks later. Methodology and principle findings  Using a population‐based surveillance system for hospitalized pneumonia and influenza‐like illness ongoing before the 2009 H1N1 pandemic began, we tracked the onset of 2009 H1N1 infection in Guatemala. We identified 239 individuals infected with influenza A (2009 H1N1) between May and December 2009, of whom 76 were hospitalized with pneumonia and 11 died (case fatality proportion: 4·6%, 95% confidence interval [CI] 2·3–8·1%). The median age of patients infected with 2009 H1N1 was 8·8 years, the median age of those hospitalized with pneumonia was 4·2 years, and five (45·5%) deaths occurred in children <5 years old. Crude rates of hospitalization between May and December 2009 were highest for children <5 years old. Twenty‐one (27·6%) of the patients hospitalized with 2009 H1N1 were admitted to the intensive care unit and eight (10·5%) required mechanical ventilation. Underlying chronic conditions were noted in 14 (18·4%) of patients with pneumonia hospitalized with 2009 H1N1 infection. Conclusions and significance  Chronic illnesses may be underdiagnosed in Guatemala, making it difficult to identify this risk group for vaccination. Children 6 months to 5 years old should be among priority groups for vaccination to prevent serious consequences because of 2009 H1N1 infection.     

Clinical factors predictive of PCR positive in pandemic H1N1 2009 influenza virus infection

Please cite this paper as: Phungoen et al. (2011) Clinical factors predictive of PCR positive in pandemic H1N1 2009 influenza virus infection. Influenza and Other Respiratory Viruses 5(6), e558–e562. Objective Pandemic H1N1 2009 influenza virus (H1N1) has been spreading globally. Clinical features might be predictive and may be different among countries. Even though the PCR test is a confirmatory test for this viral infection, it is expensive and limited in most Thai health care facilities. We studied predictive factors of PCR positive in H1N1 suspected patients. Methods Consecutive patients who had influenza‐like illness less than seven days and had been tested for H1N1 by the real‐time PCR method between May and July 2009 were enrolled. Clinical data was collected and compared between those who had positive and negative PCR tests. Results There were 6494 patients had flu‐like symptoms. Of those, 166 patients were done PCR test and 75 patients (45·18%) had positive PCR test. There were four predictors for positive PCR test including history of contact with confirmed H1N1 patients, headache, body temperature, and coryza with the adjusted odds ratio (95% confidence interval) of 2·84 (1·09–7·40), 6·25 (1·42–27·49), 1·69 (1·08–2·66), and 0·31 (0·12–0·79), respectively. Conclusions Clinical factors can be both suggestive and protective factors for H1N1 infection. These factors may be helpful in clinical practice to assess the possibility of the H1N1 infection in people who are at risk; particularly in resource‐limited health care facilities.     

An outbreak of the 2009 influenza a (H1N1) virus in a children's hospital

Please cite this paper as: Bearden et al. (2012) An outbreak of the 2009 influenza a (H1N1) virus in a children’s hospital. Influenza and Other Respiratory Viruses 6(5), 374–379. Context Preventing nosocomial transmission of influenza is essential to reduce the morbidity and mortality associated with this infection. In October 2009, an outbreak of the 2009 influenza A (H1N1) virus occurred in a hematology ward of a children’s hospital over a 21‐day period and involved two patients and four healthcare workers. Objective To investigate nosocomial transmission of the 2009 influenza A (H1N1) virus in patients and healthcare workers. Design, setting, and participants An outbreak investigation was initiated in response to suspected nosocomial transmission of the 2009 influenza A (H1N1) virus during the peak of the 2009 pandemic. Cases were confirmed using a polymerase chain reaction (PCR) test specific for the 2009 H1N1 influenza A virus. Viruses isolated from nasopharyngeal swabs were genetically characterized using Sanger sequencing of uncloned “bulk” PCR products. Main outcome measures Virus sequencing to investigate nosocomial transmission. Results Two immunocompromised patients and four healthcare workers were found to be part of a nosocomial outbreak of the 2009 influenza A (H1N1) virus. One immunocompromised patient had a second episode of clinical influenza infection after isolation precautions had been discontinued, resulting in additional exposures. Strain‐specific PCR showed that all cases were caused by infection of the 2009 H1N1 virus. Sequencing of viral genes encoding hemagglutinin and polymerase basic subunit 2 (PB2) revealed that all viruses isolated were genetically identical at these loci, including the two episodes occurring in the same immunocompromised patient. Conclusions Prompt institution of isolation precautions is essential in preventing nosocomial outbreaks of the 2009 novel influenza A (H1N1) virus. Our data suggest that isolation precautions may need to be continued for a prolonged period of time in immunocompromised patients with influenza infection.     

Statistical estimates of respiratory admissions attributable to seasonal and pandemic influenza for Canada

Please cite this paper as: Schanzer et al. (2012) Statistical estimates of respiratory admissions attributable to seasonal and pandemic influenza for Canada. Influenza and Other Respiratory Viruses DOI: 10.1111/irv.12011. Background  The number of admissions to hospital for which influenza is laboratory confirmed is considered to be a substantial underestimate of the true number of admissions due to an influenza infection. During the 2009 pandemic, testing for influenza in hospitalized patients was a priority, but the ascertainment rate remains uncertain. Methods  The discharge abstracts of persons admitted with any respiratory condition were extracted from the Canadian Discharge Abstract Database, for April 2003–March 2010. Stratified, weekly admissions were modeled as a function of viral activity, seasonality, and trend using Poisson regression models. Results  An estimated 1 out of every 6·4 admissions attributable to seasonal influenza (2003–April 2009) were coded to J10 (influenza virus identified). During the 2009 pandemic (May–March 2010), the influenza virus was identified in 1 of 1·6 admissions (95% CI, 1·5–1·7) attributed to the pandemic strain. Compared with previous H1N1 seasons (2007/08, 2008/09), the influenza‐attributed hospitalization rate for persons <65 years was approximately six times higher during the 2009 H1N1 pandemic, whereas for persons 75 years or older, the pandemic rate was approximately fivefold lower. Conclusions  Case ascertainment was much improved during the pandemic period, with under ascertainment of admissions due to H1N1/2009 limited primarily to patients with a diagnosis of pneumonia.     

Clinical epidemiology comparison of H1N1 RT-PCR-positive and RT-PCR-negative pneumonia during the 2009-2010 pandemic in Mansoura University hospitals, Egypt

Please cite this paper as: Ahmed et al. (2011) Clinical epidemiology comparison of H1N1 RT‐PCR‐positive and RT‐PCR‐negative pneumonia during the 2009–2010 pandemic in Mansoura University hospitals, Egypt. Influenza and Other Respiratory Viruses 5(4), 241–246 Background Worldwide, the infectivity and disease burden of the H1N1 pandemic were overestimated because of limited clinical experience concerning patient presentation and outcome of those infected with the novel H1N1 virus. Objective This study aimed to compare the epidemiologic clinical data among H1N1 RT‐PCR‐positive and RT‐PCR‐negative pneumonic patients during the 2009–2010 pandemic in Mansoura University Hospitals, Egypt. Methods A record‐based, case–control study was conducted for 43 adult patients admitted to the chest department isolation unit with community‐acquired pneumonia during the 2009–2010 H1N1 pandemic after reviewing of 198 suspected and confirmed H1N1 hospitalized cases. Of these patients, 20 cases were confirmed to be H1N1‐positive using an RT‐PCR detection technique. The remaining 23 patients were RT‐PCR‐negative. Demographic, clinical, laboratory and radiological data were collected and analyzed using spss version 11. Results A review of 198 hospital case records for revealed one main peak of H1N1 influenza during the last week of December 2009. Pneumonic patients who were H1N1‐positive were more likely to present with sore throat (P = 0·005), dyspnea (P = 0·002), and gastrointestinal (GIT) complaints (vomiting and diarrhea P = 0·02) when compared to the H1N1‐negative group. Also, complications were significantly more frequent (P = 0·01) in the H1N1‐confirmed group than in the non‐confirmed group. However, no significant differences were found between the groups regarding length of hospital stay, intensive care unit (ICU), and admission or mortality. Conclusion Sore throat, dyspnea, and presence of GIT complaints increase the suspicion of H1N1 positivity in pneumonia acquired during an H1N1 pandemic. However, H1N1 did not worsen the disease burden of pneumonia.     

Prior infection with classical swine H1N1 influenza viruses is associated with protective immunity to the 2009 pandemic H1N1 virus

Please cite this paper as: Kash et al. (2010) Prior infection with classical swine H1N1 influenza viruses is associated with protective immunity to the 2009 pandemic H1N1 virus. Influenza and Other Respiratory Viruses 4(3), 121–127. Background  The 2009 H1N1 pandemic emerged even though seasonal H1N1 viruses have circulated for decades. Epidemio‐logical evidence suggested that the current seasonal vaccine did not offer significant protection from the novel pandemic, and that people over the age of 50 might were less susceptible to infection. Objectives  In a mouse challenge study with the 2009 pandemic H1N1 virus, we evaluated protective immune responses elicited by prior infection with human and swine influenza A viruses. Results  Mice infected with A/Mexico/4108/2009 (Mex09) showed significant weight loss and 40% mortality. Prior infection with a 1976 classical swine H1N1 virus resulted in complete protection from Mex09 challenge. Prior infection with either a 2009 or a 1940 seasonal H1N1 influenza virus provided partial protection and a >100‐fold reduction in viral lung titers at day 4 post‐infection. Conclusions  These findings indicate that in experimental animals recently induced immunity to 1918‐derived H1N1 seasonal influenza viruses, and to a 1976 swine influenza virus, afford a degree of protection against the 2009 pandemic virus. Implications of these findings are discussed in the context of accumulating data suggesting partial protection of older persons during the 2009 pandemic.     

Co-infection in patients with hypoxemic pneumonia due to COVID-19 in Reunion Island

This study aimed to evaluate the incidence of co-infection with different types of pathogens in patients with hypoxemic pneumonia due to coronavirus disease 2019 (COVID-19) in Reunion Island.This observational study using a prospectively collected database of hypoxemic pneumonia due to COVID-19 cases was conducted at Félix Guyon University Hospital in Reunion Island, France.Between 18 March 2020 and 15 April 2020, 156 patients were admitted to our hospital for COVID-19. A total of 36 patients had hypoxemic pneumonia (23.1%) due to COVID-19. Thirty of these cases (83.3%) were imported by travelers returning mainly from metropolitan France and Spain. Patients were screened for co-infection with other pathogens at admission: 31 (86.1%) by multiplex polymerase chain reaction (PCR) and 16 (44.4%) by cytobacteriological examination of sputum culture. Five patients (13.9%) were found to have co-infection: 1 with influenza virus A H1N1 (pdm09) associated with Branhamella catarrhalis, 1 with Streptococcus pneumoniae associated with Haemophilus influenzae, 1 with Human Coronavirus 229E, 1 with Rhinovirus, and 1 with methicillin-susceptible Staphylococcus aureus. Patients with co-infection had higher D-dimer levels than those without co-infection (1.36 [1.34–2.36] μg/mL vs 0.63 [0.51–1.12] μg/mL, P = .05).The incidence of co-infection in our cohort was higher than expected (13.9%). Three co-infections (with influenza virus A(H1N1) pdm09, Streptococcus pneumoniae, and Staphylococcus aureus) required specific treatment. Patients with hypoxemic pneumonia due to COVID-19 should be screened for co-infection using respiratory cultures or multiplex PCR. Whilst our study has a number of limitations, the results from our study suggest that in the absence of screening, patients should be commenced on treatment for co-infection in the presence of an elevated D-dimer.     

Epidemiologic Observations from Passive and Targeted Surveillance during the First Wave of the 2009 H1N1 Influenza Pandemic in Milwaukee,WI

The first wave of the 2009 influenza H1N1 pandemic (H1N1pdm) in Milwaukee, WI has been recognized as the largest reported regional outbreak in the United States. The epidemiologic and clinical characteristics of this large first wave outbreak from April 28^th 2009–July 25^th 2009, studied using both passive and targeted surveillance methodologies are presented. A total of 2791 individuals with H1N1pdm infection were identified; 60 % were 5–18 years old. The 5–18 year and 0–4 year age groups had high infection (1131 and 1101 per 100,000) and hospitalization (49 and 12 per 100,000) rates respectively. Non-Hispanic blacks and Hispanics had the highest hospitalization and infection rates. In targeted surveillance, infected patients had fever (78%), cough (80%), sore throat (38%), and vomiting or diarrhea (8%). The “influenza like illness” definition captured only 68 % of infected patients. Modeling estimates that 10.3 % of Milwaukee population was infected in the first wave and 59% were asymptomatic. The distinct epidemiologic profile of H1N1pdm infections observed in the study has direct implications for predicting the burden of infection and hospitalization in the next waves of H1N1pdm. Careful consideration of demographic predictors of infection and hospitalization with H1N1pdm will be important for effective preparedness for subsequent influenza seasons.     

Original Article: A primary school outbreak of pandemic 2009 influenza A (H1N1) in China

Please cite this paper as: Huai et al. (2010) A primary school outbreak of pandemic 2009 influenza A (H1N1) in China. Influenza and Other Respiratory Viruses DOI: 10.1111/j.1750‐2659.2010.00150.x. Background  We investigated the first known outbreak of pandemic 2009 influenza A (H1N1) at a primary school in China. Objectives  To describe epidemiologic findings, identify risk factors associated with 2009 H1N1 illness, and inform national policy including school outbreak control and surveillance strategies. Methods  We conducted retrospective case finding by reviewing the school’s absentee log and retrieving medical records. Enhanced surveillance was implemented by requiring physicians to report any influenza‐like illness (ILI) cases to public health authorities. A case–control study was conducted to detect potential risk factors for 2009 H1N1 illness. A questionnaire was administered to 50 confirmed cases and 197 age‐, gender‐, and location‐matched controls randomly selected from student and population registries. Results  The attack rate was 4% (50/1314), and children from all grades were affected. When compared with controls, confirmed cases were more likely to have been exposed to persons with respiratory illness either in the home or classroom within 7 days of symptom onset (OR, 4·5, 95% CI: 1·9–10·7). No cases reported travel or contact with persons who had traveled outside of the country. Conclusions  Findings in this outbreak investigation, including risk of illness associated with contacting persons with respiratory illness, are consistent with those reported by others for seasonal influenza and 2009 H1N1 outbreaks in school. The outbreak confirmed that community‐level transmission of 2009 H1N1 virus was occurring in China and helped lead to changes in the national pandemic policy from containment to mitigation.     

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.     

Influenza vaccine effectiveness against influenza A subtypes in Europe: Results from the 2021–2022 I‐MOVE primary care multicentre study

BackgroundIn 2021–2022, influenza A viruses dominated in Europe. The I‐MOVE primary care network conducted a multicentre test‐negative study to measure influenza vaccine effectiveness (VE).MethodsPrimary care practitioners collected information on patients presenting with acute respiratory infection. Cases were influenza A(H3N2) or A(H1N1)pdm09 RT‐PCR positive, and controls were influenza virus negative. We calculated VE using logistic regression, adjusting for study site, age, sex, onset date, and presence of chronic conditions.ResultsBetween week 40 2021 and week 20 2022, we included over 11 000 patients of whom 253 and 1595 were positive for influenza A(H1N1)pdm09 and A(H3N2), respectively. Overall VE against influenza A(H1N1)pdm09 was 75% (95% CI: 43–89) and 81% (95% CI: 45–93) among those aged 15–64 years. Overall VE against influenza A(H3N2) was 29% (95% CI: 12–42) and 25% (95% CI: −41 to 61), 33% (95% CI: 14–49), and 26% (95% CI: −22 to 55) among those aged 0–14, 15–64, and over 65 years, respectively. The A(H3N2) VE among the influenza vaccination target group was 20% (95% CI: −6 to 39). All 53 sequenced A(H1N1)pdm09 viruses belonged to clade 6B.1A.5a.1. Among 410 sequenced influenza A(H3N2) viruses, all but eight belonged to clade 3C.2a1b.2a.2.DiscussionDespite antigenic mismatch between vaccine and circulating strains for influenza A(H3N2) and A(H1N1)pdm09, 2021–2022 VE estimates against circulating influenza A(H1N1)pdm09 were the highest within the I‐MOVE network since the 2009 influenza pandemic. VE against A(H3N2) was lower than A(H1N1)pdm09, but at least one in five individuals vaccinated against influenza were protected against presentation to primary care with laboratory‐confirmed influenza.     

58例甲型H1N1流感病毒性肺炎临床分析

目的探讨H1N1流感病毒性肺炎的临床特点、治疗以及预后。方法回顾性分析我院2009年10月31日-2010年1月15日58例H1N1流感病毒性肺炎的临床资料,并对重症病例、发病年龄、基础病、呼吸道症状、影像学资料、治疗及预后进行分析。结果 58例患者临床特点为：高热,咳白色粘液痰,可引起呼吸衰竭,全胸片或胸部CT示肺部斑片状致密影或磨玻璃影。治疗以奥司他韦,糖皮质激素为主,必要时予机械通气,辅以营养支持等,其中20例符合重症肺炎的诊断结果,4例并发ARDS,4例并发多脏器功能障碍,3例死亡。结论及早诊断和治疗,是提高治愈率的关键。