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The Relationship Between 2009 Pandemic H1N1 Influenza During Pregnancy and Preterm Birth: A Population-based Cohort Study. Epidemiology 2018; 29:107-116. [PMID: 28930786 DOI: 10.1097/ede.0000000000000753] [Citation(s) in RCA: 23] [Impact Index Per Article: 3.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/26/2022]
Abstract
BACKGROUND Previous studies of maternal influenza illness and preterm birth have yielded inconsistent results. Our objective was to assess the association between 2009 pandemic H1N1 (pH1N1) influenza during pregnancy and preterm birth in a large obstetrical population. METHODS We linked a province-wide birth registry with health administrative databases to identify influenza-coded hospitalizations, emergency department visits, or physician visits among pregnant women during the 2009 H1N1 pandemic (our proxy for clinical pH1N1 influenza illness). Using Cox regression, we estimated adjusted hazard ratios (aHR) for preterm birth and spontaneous preterm birth treating influenza as a time-varying exposure. RESULTS Among 192,082 women with a singleton live birth, 2,925 (1.5%) had an influenza-coded health care encounter during the 2009 H1N1 pandemic. Compared with unexposed pregnancy time, there was no association between exposure to the pandemic, with or without clinical influenza illness, and preterm birth (no pH1N1 diagnosis: aHR = 1.0; 95% confidence interval [CI] = 0.98, 1.1; pH1N1 diagnosis: aHR = 1.0; 95% CI = 0.88, 1.2). Among women with preexisting medical conditions, influenza was associated with increased preterm birth (aHR = 1.5; 95% CI = 1.1, 2.2) and spontaneous preterm birth (aHR = 1.7; 95% CI = 1.1, 2.6), and these associations were strongest in the third trimester and when data were analyzed to allow for a transient acute effect of influenza. CONCLUSIONS In the general obstetrical population, there was no association between pH1N1 influenza illness and preterm birth, but women with preexisting medical conditions known to increase the risk of influenza-associated morbidity were at elevated risk.
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Pandemic H1N1 Vaccination and Incidence of Acute Disseminated Encephalomyelitis in Manitoba. Can J Neurol Sci 2016; 43:819-823. [DOI: 10.1017/cjn.2016.291] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/02/2023]
Abstract
AbstractBackground: An increased incidence of hospital admissions coded as acute disseminated encephalomyelitis (ADEM) was noted in Winnipeg, Manitoba, Canada, during the second wave of the influenza pandemic from October 2009 to March 2010. However, it was not clear whether this was due to heightened awareness of potential neurological complications of influenza or influenza vaccination or an actual increase in the number of cases. Methods: We extracted data from the charts of 139 patients hospitalized with an International Classification of Diseases-10 discharge code indicating ADEM (G04.0) or unspecified noninfectious encephalitis or myelitis (G04.8, G04.9) between January 2006 and December 2012. Clinical and laboratory data were reviewed by a neurologist, and diagnoses were determined using the Brighton criteria. Results: Over the entire study period, there were 22 cases of ADEM. During the peak pandemic period (April-December 2009), seven patients were hospitalized with ADEM, corresponding to a rate of 7.8/million/year; 4.7 (95% confidence interval: 1.9-11.4) times higher than the rate before or after the pandemic period. Only one patient with ADEM had received the monovalent A(H1N1)pdm09 vaccine within 12 weeks of hospitalization. Conclusions: We have found an increased incidence of ADEM during the pandemic period that may be related, at least in part, to the increased incidence of influenza during that period. However, there was no temporal relationship with the administration of A(H1N1)pdm09 or seasonal influenza vaccines. Our study provides reassurance that use of these vaccines was not associated with increased risk of ADEM.
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Fell DB, Buckeridge DL, Platt RW, Kaufman JS, Basso O, Wilson K. Circulating Influenza Virus and Adverse Pregnancy Outcomes: A Time-Series Study. Am J Epidemiol 2016; 184:163-75. [PMID: 27449415 DOI: 10.1093/aje/kww044] [Citation(s) in RCA: 11] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/14/2015] [Accepted: 02/19/2016] [Indexed: 11/14/2022] Open
Abstract
Individual-level epidemiologic studies of pregnancy outcomes after maternal influenza are limited in number and quality and have produced inconsistent results. We used a time-series design to investigate whether fluctuation in influenza virus circulation was associated with short-term variation in population-level rates of preterm birth, stillbirth, and perinatal death in Ontario between 2003 and 2012. Using Poisson regression, we assessed the association between weekly levels of circulating influenza virus and counts of outcomes offset by the number of at-risk gestations during 3 gestational exposure windows. The rate of preterm birth was not associated with circulating influenza level in the week preceding birth (adjusted rate ratio = 1.01, 95% confidence interval: 1.00, 1.02) or in any other exposure window. These findings were robust to alternate specifications of the model and adjustment for potential confounding. Stillbirth and perinatal death rates were similarly not associated with gestational exposure to influenza circulation during late pregnancy. We could not assess mortality outcomes relative to early gestational exposure because of missing dates of conception for many stillbirths. In this time-series study, population-level influenza circulation was not associated with short-term variation in rates of preterm birth, stillbirth, or perinatal death.
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Did the H1N1 Vaccine Reduce the Risk of Admission with Influenza and Pneumonia during the Pandemic? PLoS One 2015; 10:e0142754. [PMID: 26600435 PMCID: PMC4658136 DOI: 10.1371/journal.pone.0142754] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/04/2015] [Accepted: 10/26/2015] [Indexed: 01/23/2023] Open
Abstract
Background The extent to which A(H1N1)pdm09 influenza vaccines prevented hospital admissions with pneumonia and influenza (P&I) during the 2009 pandemic remains poorly understood. We evaluated the effectiveness of the A(H1N1)pdm09 and seasonal influenza vaccines (TIV) used during the 2009 mass vaccination campaign in Manitoba (Canada) in preventing P&I hospitalization. Methods A population-based record-linkage nested case-control study. Cases (N = 1,812) were persons hospitalized with influenza (ICD-10:J09-J11) or pneumonia (ICD-10:J12-J18) during the study period. Age-, gender- and area of residence-matched controls (N = 7,915) were randomly sampled from Manitoba’s Population Registry. Information on receipt of A(H1N1)pdm09 vaccine and TIV was obtained from the Manitoba Immunization Monitoring System, a province-wide vaccine registry. Results Overall, the adjuvanted A(H1N1)pdm09 vaccine was 27% (95%CI 13–39%) effective against P&I hospitalization ≥ 14 days following administration. Effectiveness seemed lower among older (≥ 65 years) adults (10%; −16–30%), particularly when compared to under-5 children (58%; 30–75%). The number-needed-to-vaccinate to prevent 1 P&I admission was lowest among <4 year-olds (928) and ≥65 years (1,721). VE against hospitalization with laboratory-confirmed A(H1N1)pdm09 was 70% (39–85%) overall and (91%; 62–98%) ≥ 14 days following vaccination. Discussion Our data suggest that the adjuvanted A(H1N1)pdm09 vaccine was effective in preventing about 55–60% of P&I hospitalizations among children and younger adults who were at much higher risk of infection. Unfortunately, the vaccine was less effective among 65 or older adults. Despite that the vaccine still had a significant population-based impact especially among the very young (<5) and the older (≥ 65 years).
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Hinds AM, Bozat-Emre S, Van Caeseele P, Mahmud SM. Comparison of the epidemiology of laboratory-confirmed influenza A and influenza B cases in Manitoba, Canada. BMC Public Health 2015; 15:35. [PMID: 25633280 PMCID: PMC4331145 DOI: 10.1186/s12889-015-1351-z] [Citation(s) in RCA: 12] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/16/2014] [Accepted: 01/05/2015] [Indexed: 11/10/2022] Open
Abstract
Background Despite the public health significance of annual influenza outbreaks, the literature comparing the epidemiology of influenza A and B infections is limited and dated and may not reflect recent trends. In Canada, the relative contribution of influenza A and B to the burden of morbidity is not well understood. We examined rates of laboratory-confirmed cases of influenza A and B (LCI-A and LCI-B) in the Canadian province of Manitoba between 1993 and 2008 and compared cases of the two types in terms of socio-demographic and clinical characteristics. Methods Laboratory-confirmed cases of influenza A and B in Manitoba between 1993 and 2008 were identified from the Cadham Provincial Laboratory (CPL) Database and linked to de-identified provincial administrative health records. Crude and age-adjusted incidence rates of LCI-A and LCI-B were calculated. Demographic characteristics, health status, health service use, and vaccination history were compared by influenza type. Results Over the study period, 1,404 of LCI-A and 445 cases of LCI-B were diagnosed, corresponding to an annual age-standardized rate of 7.2 (95% CI: 6.5-7.9) for LCI-A and 2.2 (CI: 1.5 – 3.0) per 100,000 person-years for LCI-B. Annual rates fluctuated widely but there was less variation in the LCI-B rates. For LCI-A, but not LCI-B, incidence was inversely related to household income. Older age, urban residence and past hospitalization were associated with increased detection of LCI-A whereas receipt of the influenza vaccine was associated with decreased LCI-A detection. Once socio-demographic variables were controlled, having a pre-existing chronic disease or immune suppression was not related to influenza type. Conclusion Influenza A and B affected different segments of the population. Older age was associated with increased LCI-A detection, but not with pre-existing chronic diseases. This information may be useful to public health professionals in planning and evaluating new and existing seasonal influenza vaccines.
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Affiliation(s)
- Aynslie M Hinds
- Vaccine and Drug Evaluation Centre, Department of Community Health Sciences, Faculty of Health Sciences, University of Manitoba, S111 - 750 Bannatyne Avenue, Winnipeg, Manitoba, R3E 0W3, Canada.
| | - Songul Bozat-Emre
- Vaccine and Drug Evaluation Centre, Department of Community Health Sciences, Faculty of Health Sciences, University of Manitoba, S111 - 750 Bannatyne Avenue, Winnipeg, Manitoba, R3E 0W3, Canada.
| | - Paul Van Caeseele
- Department of Medical Microbiology, Faculty of Medicine, University of Manitoba, Winnipeg, Manitoba, Canada. .,Cadham Provincial Laboratory, Winnipeg, Manitoba, Canada.
| | - Salaheddin M Mahmud
- Vaccine and Drug Evaluation Centre, Department of Community Health Sciences, Faculty of Health Sciences, University of Manitoba, S111 - 750 Bannatyne Avenue, Winnipeg, Manitoba, R3E 0W3, Canada. .,Faculty of Pharmacy, University of Manitoba, Winnipeg, Manitoba, Canada.
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Schillberg E, Isaac M, Deng X, Peirano G, Wylie JL, Van Caeseele P, Pillai DR, Sinnock H, Mahmud SM. Outbreak of invasive Streptococcus pneumoniae serotype 12F among a marginalized inner-city population in Winnipeg, Canada, 2009-2011. Clin Infect Dis 2014; 59:651-7. [PMID: 24842908 DOI: 10.1093/cid/ciu366] [Citation(s) in RCA: 31] [Impact Index Per Article: 3.1] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/29/2022] Open
Abstract
BACKGROUND In 2010, Winnipeg, Canada, experienced a doubling of invasive pneumococcal disease (IPD) rates, with a significant increase in the number of cases due to Streptococcus pneumoniae serotype 12F, which previously had accounted for very few cases each year. METHODS All serotype 12F IPD cases reported between September 2009 and January 2011 were reviewed. Pulsed-field gel electrophoresis (PFGE) and multilocus variable number tandem repeat analysis (MLVA) were conducted on all isolates. PFGE and MLVA patterns identified several possible clusters. Additional interviews were conducted to obtain information on risk factors and outcomes. RESULTS Between September 2009 and January 2011, 169 cases of IPD were identified. The number of IPD cases due to 12F serotype increased sharply from about 3-4 cases per year (6% of IPD cases) in 2007-2009 to 28 (29%) in 2010. All 12F isolates belonged to a single sequence type (ST218), and they were generally susceptible to penicillin and fluoroquinolones but not to erythromycin. Compared with cases caused by other serotypes, patients with serotype 12F were more likely to be homeless, reside in low-income inner-city communities, and engage in substance abuse, including intravenous and crack cocaine use. Subclusters identified using MLVA had even higher rates of homelessness and substance use. CONCLUSIONS An immunization campaign targeting high-risk groups was undertaken with pneumococcal polysaccharide vaccine, and subsequently rates of serotype 12F decreased. To our knowledge, this is the largest documented community outbreak of serotype 12F IPD and the first report of an outbreak of IPD serotype 12F in a marginalized urban population in Canada.
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Affiliation(s)
| | - Michael Isaac
- Vaccine and Drug Evaluation Centre, Department of Community Health Sciences, University of Manitoba, Winnipeg
| | - Xianding Deng
- Department of Laboratory Medicine and Pathobiology, University of Toronto
| | - Gisele Peirano
- Department of Pathology and Laboratory Medicine, University of Calgary Calgary Laboratory Services
| | - John L Wylie
- Cadham Provincial Laboratory Department of Medical Microbiology
| | | | - Dylan R Pillai
- Department of Pathology and Laboratory Medicine, University of Calgary Calgary Laboratory Services
| | - Hasantha Sinnock
- Vaccine and Drug Evaluation Centre, Department of Community Health Sciences, University of Manitoba, Winnipeg
| | - Salaheddin M Mahmud
- Winnipeg Regional Health Authority Vaccine and Drug Evaluation Centre, Department of Community Health Sciences, University of Manitoba, Winnipeg Faculty of Pharmacy, University of Manitoba, Winnipeg, Canada
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Ray JG, McGeer AJ, Blake JM, Lebovic G, Smith GN, Yudin MH. Peripartum outcomes: non-adjuvanted v. adjuvanted H1N1 vaccination. CMAJ 2014; 186:137. [PMID: 24492526 DOI: 10.1503/cmaj.114-0006] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/01/2022] Open
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Fléchelles O, Fowler R, Jouvet P. H1N1 pandemic: clinical and epidemiologic characteristics of the Canadian pediatric outbreak. Expert Rev Anti Infect Ther 2014; 11:555-63. [PMID: 23750727 DOI: 10.1586/eri.13.40] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/12/2023]
Abstract
Canada was one of the first countries affected by the 2009 influenza H1N1 pandemic with two waves - one from May to June and one from October to December. The 2009 influenza H1N1 pandemic had many unique features when compared with seasonal influenza, including the following: more than half of the affected people were children; asthma was the most significant risk factor for hospital admission; and Aboriginal and pregnant women had a higher risk of hospital admission and complications. Antiviral therapy was widely used but data did not show any effect on the pediatric population. Outbreak spread was possibly promoted from child-child and child-adult contact, and therefore the vaccination campaign targeted the pediatric population and achieved good coverage among young children (57%). Vaccination efficacy was difficult to test because of the vaccination delay. Improvement in models of prevention and treatment are urgently needed to prepare for the possible future pandemics.
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Doyle TJ, Goodin K, Hamilton JJ. Maternal and neonatal outcomes among pregnant women with 2009 pandemic influenza A(H1N1) illness in Florida, 2009-2010: a population-based cohort study. PLoS One 2013; 8:e79040. [PMID: 24205364 PMCID: PMC3812024 DOI: 10.1371/journal.pone.0079040] [Citation(s) in RCA: 59] [Impact Index Per Article: 5.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/08/2013] [Accepted: 09/18/2013] [Indexed: 11/18/2022] Open
Abstract
Introduction Pregnant women have been identified as a high risk group for severe illness with 2009 pandemic influenza A(H1N1) virus infection (pH1N1). Obesity has also been identified as a risk factor for severe illness, though this has not been thoroughly assessed among pregnant women. The objectives of this study were to provide risk estimates for adverse maternal and neonatal outcomes associated with pH1N1 illness during pregnancy and to assess the role of obesity in these outcomes. Methods We established a retrospective population-based cohort of all live births occurring in Florida during the first 15 months of the pandemic. Illness with pH1N1 during pregnancy was ascertained through record linkage with the Florida state notifiable disease surveillance database. Data from the birth record, including pre-pregnancy body mass index, were analyzed to assess risk of adverse outcomes associated with pH1N1 illness. Results A total of 194 women were identified through surveillance with pH1N1 illness during pregnancy. Children born to women with pH1N1 illness during pregnancy were at increased risk for low birth weight [OR (95%CI): 1.78 (1.11-2.860)], premature birth [2.21 (1.47-3.330)], and infant death [4.46 (1.80-11.00)], after adjusting for other factors. Women with pH1N1 illness during pregnancy were at increased risk for severe outcomes including admission to an intensive care unit. Obesity was an observed risk factor, both for the more severe pH1N1 illness detected through surveillance, and for severe maternal outcomes. Conclusions Case-patients in this analysis likely represent the most severely ill subset of all women infected with pH1N1 during pregnancy, limiting the generalizability of these findings to more severely ill patients rather than influenza infection in general. Nevertheless, these results suggest that more severe pH1N1 illness during pregnancy is associated with adverse neonatal outcomes and that pregnant women should continue to be targeted for appropriate prophylaxis and early treatment.
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Affiliation(s)
- Timothy J. Doyle
- Florida Department of Health, Bureau of Epidemiology, Tallahassee, Florida, United States of America
- Centers for Disease Control and Prevention, Atlanta, Georgia, United States of America
- * E-mail:
| | - Kate Goodin
- Florida Department of Health, Bureau of Epidemiology, Tallahassee, Florida, United States of America
| | - Janet J. Hamilton
- Florida Department of Health, Bureau of Epidemiology, Tallahassee, Florida, United States of America
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He D, Dushoff J, Eftimie R, Earn DJD. Patterns of spread of influenza A in Canada. Proc Biol Sci 2013; 280:20131174. [PMID: 24026815 DOI: 10.1098/rspb.2013.1174] [Citation(s) in RCA: 27] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/29/2022] Open
Abstract
Understanding spatial patterns of influenza transmission is important for designing control measures. We investigate spatial patterns of laboratory-confirmed influenza A across Canada from October 1999 to August 2012. A statistical analysis (generalized linear model) of the seasonal epidemics in this time period establishes a clear spatio-temporal pattern, with influenza emerging earlier in western provinces. Early emergence is also correlated with low temperature and low absolute humidity in the autumn. For the richer data from the 2009 pandemic, a mechanistic mathematical analysis, based on a transmission model, shows that both school terms and weather had important effects on pandemic influenza transmission.
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Affiliation(s)
- Daihai He
- Department of Applied Mathematics, Hong Kong Polytechnic University, , Hung Hom, Kowloon, Hong Kong (SAR), People's Republic of China, Department of Biology, McMaster University, , Hamilton, Ontario, Canada , L8S 4L8, M.G. DeGroote Institute for Infectious Disease Research, McMaster University, , Hamilton, Ontario, Canada , L8S 4L8, Division of Mathematics, University of Dundee, , Dundee DD1 4HN, UK, Department of Mathematics and Statistics, McMaster University, , Hamilton, Ontario, Canada , L8S 4K1
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Serological survey of the novel influenza A H1N1 in inner city Winnipeg, Manitoba, 2009. CANADIAN JOURNAL OF INFECTIOUS DISEASES & MEDICAL MICROBIOLOGY 2013; 23:65-70. [PMID: 23730311 DOI: 10.1155/2012/484693] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 11/18/2022]
Abstract
INTRODUCTION Little is known about the determinants of pandemic H1N1 (pH1N1) infection in Canada among low-income, inner city populations. To inform future influenza planning, the seroprevalence of pH1N1 antibodies among inner city clinic attendees in Winnipeg (Manitoba) according to sociodemographic and risk factor characteristics were estimated and vaccination rates were explored. METHODS Adults presenting to three inner city community clinics in Winnipeg from October 2009 to December 2009 were recruited as study participants (n=458). A questionnaire was administered to collect demographic, risk factor and symptom information, and a venous blood sample was collected for hemagglutination inhibition assay testing to detect the presence of antibodies against pH1N1. RESULTS Approximately one-half (53%) of the study participants reported an annual household income of <$10,000/year, and 65% identified as Aboriginal. pH1N1 positivity was 5.7% among those enrolled early in the study and 15.5% among those enrolled later in the study. Positivity was higher among participants who were female, Aboriginal and in contact with children ≤5 years of age. The overall pH1N1 vaccination rate was 28%. DISCUSSION pH1N1 positivity was high among low-income adults accessing clinics in Winnipeg's inner city compared with the general population. Of further concern were the low rates of uptake of both seasonal and pH1N1 influenza vaccinations. When planning for future influenza outbreaks, it is important to incorporate strategies for the prevention, control, and care of influenza among low-income and inner city adults.
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Laurie KL, Huston P, Riley S, Katz JM, Willison DJ, Tam JS, Mounts AW, Hoschler K, Miller E, Vandemaele K, Broberg E, Van Kerkhove MD, Nicoll A. Influenza serological studies to inform public health action: best practices to optimise timing, quality and reporting. Influenza Other Respir Viruses 2013; 7:211-24. [PMID: 22548725 PMCID: PMC5855149 DOI: 10.1111/j.1750-2659.2012.0370a.x] [Citation(s) in RCA: 42] [Impact Index Per Article: 3.8] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/30/2022] Open
Abstract
BACKGROUND Serological studies can detect infection with a novel influenza virus in the absence of symptoms or positive virology, providing useful information on infection that goes beyond the estimates from epidemiological, clinical and virological data. During the 2009 A(H1N1) pandemic, an impressive number of detailed serological studies were performed, yet the majority of serological data were available only after the first wave of infection. This limited the ability to estimate the transmissibility and severity of this novel infection, and the variability in methodology and reporting limited the ability to compare and combine the serological data. OBJECTIVES To identify best practices for conduct and standardisation of serological studies on outbreak and pandemic influenza to inform public policy. METHODS/SETTING An international meeting was held in February 2011 in Ottawa, Canada, to foster the consensus for greater standardisation of influenza serological studies. RESULTS Best practices for serological investigations of influenza epidemiology include the following: classification of studies as pre-pandemic, outbreak, pandemic or inter-pandemic with a clearly identified objective; use of international serum standards for laboratory assays; cohort and cross-sectional study designs with common standards for data collection; use of serum banks to improve sampling capacity; and potential for linkage of serological, clinical and epidemiological data. Advance planning for outbreak studies would enable a rapid and coordinated response; inclusion of serological studies in pandemic plans should be considered. CONCLUSIONS Optimising the quality, comparability and combinability of influenza serological studies will provide important data upon emergence of a novel or variant influenza virus to inform public health action.
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Affiliation(s)
- Karen L Laurie
- WHO Collaborating Centre for Reference and Research on Influenza, VIDRL, North Melbourne, Vic. 3051, Australia.
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Pandemic influenza H1N1: reconciling serosurvey data with estimates of the reproduction number. Epidemiology 2012; 23:86-94. [PMID: 22089631 DOI: 10.1097/ede.0b013e31823a44a5] [Citation(s) in RCA: 15] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/27/2022]
Abstract
BACKGROUND During the 2009 pandemic of influenza A (H1N1), many studies reported estimates of the reproduction number from outbreak data. Since then, seroprevalence studies have been conducted in a number of countries to assess the proportion of the population that was infected in the first wave of the pandemic. METHODS Here, we collate the reproduction number estimates, and use mathematical models to reconcile these with serosurvey data. RESULTS Most estimates of the reproduction number from outbreaks are in the range of 1.0-2.0, whereas mean estimates calculated from seroprevalence data range from 1.14 to 1.36. Age-specific analysis of these data suggests that the reproduction number for children was approximately 1.6, whereas the reproduction numbers for adults >25 years of age was less than 1.0. CONCLUSION The difference between age-groups may help to explain high estimates of the reproduction number from outbreaks involving a large proportion of child cases.
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Liu SL, Wang J, Yang XH, Chen J, Huang RJ, Ruan B, He HX, Wang CM, Zhang HM, Sun Z, Xie L, Zhuang H. Pandemic influenza A(H1N1) 2009 virus in pregnancy. Rev Med Virol 2012; 23:3-14. [DOI: 10.1002/rmv.1712] [Citation(s) in RCA: 26] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/30/2011] [Revised: 02/05/2012] [Accepted: 02/08/2012] [Indexed: 11/09/2022]
Affiliation(s)
- She-Lan Liu
- Department of Infectious Diseases; Hangzhou Center for Disease Control and Prevention,Zhejiang Province Center for Disease Control and Prevention; Hangzhou Zhejiang province China
| | - Jing Wang
- Department of Infectious Diseases; Hangzhou Center for Disease Control and Prevention,Zhejiang Province Center for Disease Control and Prevention; Hangzhou Zhejiang province China
| | - Xu-Hui Yang
- Department of Infectious Diseases; Hangzhou Center for Disease Control and Prevention,Zhejiang Province Center for Disease Control and Prevention; Hangzhou Zhejiang province China
| | - Jin Chen
- Department of Infectious Diseases; Hangzhou Center for Disease Control and Prevention,Zhejiang Province Center for Disease Control and Prevention; Hangzhou Zhejiang province China
| | - Ren-Jie Huang
- Department of Infectious Diseases; Hangzhou Center for Disease Control and Prevention,Zhejiang Province Center for Disease Control and Prevention; Hangzhou Zhejiang province China
| | - Bing Ruan
- State Key Laboratory for Diagnosis and Treatment of Infectious Diseases, The First Affiliated Hospital, College of Medicine; Zhejiang University; Hangzhou Zhejiang province China
| | - Hong-Xuan He
- National Research Center for Wildlife Borne Diseases, Key Lab of Animal Ecology and Conservation Biology, Institute of Zoology; Chinese Academy of Sciences; Beijing China
| | - Cheng-Min Wang
- National Research Center for Wildlife Borne Diseases, Key Lab of Animal Ecology and Conservation Biology, Institute of Zoology; Chinese Academy of Sciences; Beijing China
| | - Hong-Mei Zhang
- Department of Hepatology, The Second Affiliated Hospital, College of Medicine; Southeast University; Nanjing Jiangsu province China
| | - Zhou Sun
- Department of Infectious Diseases; Hangzhou Center for Disease Control and Prevention,Zhejiang Province Center for Disease Control and Prevention; Hangzhou Zhejiang province China
| | - Li Xie
- Department of Infectious Diseases; Hangzhou Center for Disease Control and Prevention,Zhejiang Province Center for Disease Control and Prevention; Hangzhou Zhejiang province China
| | - Hui Zhuang
- Department of Microbiology and Infectious Disease Center, School of Basic Medical Sciences; Peking University Health Science Center; Beijing China
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Du MM, Jia N, Suo JJ, Xing YB, Zhang PH, Liu G, Xiao HJ, Zhang JS, Jia N, Gao Y, Xie LJ, Deng CY, Ren SW, Liu YX. Perinatal outcomes and congenital abnormalities in the newborns of women affected by the 2009 pandemic influenza A (H1N1) in Beijing, China. Int J Gynaecol Obstet 2011; 116:148-52. [PMID: 22093498 DOI: 10.1016/j.ijgo.2011.08.024] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/11/2011] [Revised: 08/31/2011] [Accepted: 10/18/2011] [Indexed: 10/15/2022]
Abstract
OBJECTIVE To investigate the pregnancy complications, perinatal outcomes, and congenital abnormalities (CAs) that occurred in Beijing, China, when pregnant women became infected with the 2009 pandemic influenza A (H1N1) (H1N1 pdm). METHODS Pregnancy complications, perinatal outcomes, and CAs were compared among 3 groups of pregnant women. The 23 women in group 1 were confirmed to harbor viral RNA; the 23 in group 2 had serum levels of virus-specific antibodies against H1N1 pdm, meaning that they were suspected of being infected with the virus; and the 93 in group 3 had no detectable virus-specific antibodies. RESULTS Perinatal outcomes and pregnancy complications were not significantly different in groups 1 and 3. Higher percentages of stillbirths (12.0%) and placental disorders (13.0%) were observed in group 2 than in group 3. Many women in group 2 (62.5%) experienced symptoms of having a cold during pregnancy and most took no medication. Two cases of CA occurred in group 1, in the offspring of women infected in the second trimester. CONCLUSION When left untreated, infection with the 2009 H1N1 pdm virus during pregnancy appears to have increased fetal mortality and morbidity. Because CAs are traumatic for all concerned, their possible association with the virus should be further evaluated.
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Affiliation(s)
- Ming-Mei Du
- Department of Nosocomial Infection Management and Disease Control, Institute of Hospital Management, Chinese People's Liberation Army General Hospital, Beijing, China
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Achonu C, Rosella L, Gubbay JB, Deeks S, Rebbapragada A, Mazzulli T, Willison D, Foisy J, McGeer A, Johnson I, LaFreniere M, Johnson C, Willmore J, Yue C, Crowcroft NS. Seroprevalence of pandemic influenza H1N1 in Ontario from January 2009-May 2010. PLoS One 2011; 6:e26427. [PMID: 22110586 PMCID: PMC3215698 DOI: 10.1371/journal.pone.0026427] [Citation(s) in RCA: 20] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/22/2011] [Accepted: 09/26/2011] [Indexed: 11/18/2022] Open
Abstract
BACKGROUND We designed a seroprevalence study using multiple testing assays and population sources to estimate the community seroprevalence of pH1N1/09 and risk factors for infection before the outbreak was recognized and throughout the pandemic to the end of 2009/10 influenza season. METHODS Residual serum specimens from five time points (between 01/2009 and 05/2010) and samples from two time points from a prospectively recruited cohort were included. The distribution of risk factors was explored in multivariate adjusted analyses using logistic regression among the cohort. Antibody levels were measured by hemagglutination inhibition (HAI) and microneutralization (MN) assays. RESULTS Residual sera from 3375 patients and 1024 prospectively recruited cohort participants were analyzed. Pre-pandemic seroprevalence ranged from 2%-12% across age groups. Overall seropositivity ranged from 10%-19% post-first wave and 32%-41% by the end of the 2009/10 influenza season. Seroprevalence and risk factors differed between MN and HAI assays, particularly in older age groups and between waves. Following the H1N1 vaccination program, higher GMT were noted among vaccinated individuals. Overall, 20-30% of the population was estimated to be infected. CONCLUSIONS Combining population sources of sera across five time points with prospectively collected epidemiological information yielded a complete description of the evolution of pH1N1 infection.
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Affiliation(s)
- Camille Achonu
- Department of Surveillance and Epidemiology, Public Health Ontario, Toronto, Ontario, Canada
| | - Laura Rosella
- Department of Surveillance and Epidemiology, Public Health Ontario, Toronto, Ontario, Canada
- Dalla Lana School of Public Health, University of Toronto, Toronto, Ontario, Canada
| | - Jonathan B. Gubbay
- Public Health Laboratories, Public Health Ontario, Toronto, Ontario, Canada
- Department of Laboratory Medicine and Pathobiology, University of Toronto, Toronto, Ontario, Canada
| | - Shelley Deeks
- Department of Surveillance and Epidemiology, Public Health Ontario, Toronto, Ontario, Canada
- Dalla Lana School of Public Health, University of Toronto, Toronto, Ontario, Canada
| | - Anu Rebbapragada
- Public Health Laboratories, Public Health Ontario, Toronto, Ontario, Canada
| | - Tony Mazzulli
- Public Health Laboratories, Public Health Ontario, Toronto, Ontario, Canada
| | - Don Willison
- Department of Surveillance and Epidemiology, Public Health Ontario, Toronto, Ontario, Canada
| | - Julie Foisy
- Department of Surveillance and Epidemiology, Public Health Ontario, Toronto, Ontario, Canada
| | - Allison McGeer
- Dalla Lana School of Public Health, University of Toronto, Toronto, Ontario, Canada
- Department of Microbiology, Mount Sinai Hospital, Toronto, Ontario, Canada
| | - Ian Johnson
- Department of Surveillance and Epidemiology, Public Health Ontario, Toronto, Ontario, Canada
- Dalla Lana School of Public Health, University of Toronto, Toronto, Ontario, Canada
| | - Marie LaFreniere
- Department of Surveillance and Epidemiology, Public Health Ontario, Toronto, Ontario, Canada
| | - Caitlin Johnson
- Department of Surveillance and Epidemiology, Public Health Ontario, Toronto, Ontario, Canada
| | | | - Carmen Yue
- Toronto Public Health, Toronto, Ontario, Canada
| | - Natasha S. Crowcroft
- Department of Surveillance and Epidemiology, Public Health Ontario, Toronto, Ontario, Canada
- Dalla Lana School of Public Health, University of Toronto, Toronto, Ontario, Canada
- Department of Laboratory Medicine and Pathobiology, University of Toronto, Toronto, Ontario, Canada
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17
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Reinheimer C, Doerr HW, Friedrichs I, Stürmer M, Allwinn R. H1N1v at a seroepidemiological glance: is the nightmare over? Eur J Clin Microbiol Infect Dis 2011; 31:1467-71. [PMID: 22065279 DOI: 10.1007/s10096-011-1465-x] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/06/2011] [Accepted: 10/01/2011] [Indexed: 11/25/2022]
Abstract
When the second wave of pandemic influenza A H1N1v 2009 (H1N1v) emerged in the winter of 2010/2011, public health authorities were afraid of dangerous implications and severe clinical courses again. As further H1N1v waves might appear, achievement of sufficient herd immunity is a matter of urgency. The objective of this study was to determine the seroprevalence of antibodies against H1N1v by hemagglutination-inhibition test (HI) after the second wave. We compared our recent findings with our data obtained after the first pandemic in 2009/2010. Between March and May 2011 we collected serum samples from 600 persons aged 1 to 84 years admitted to University Hospital Frankfurt/Main and analysed the titres of anti-H1N1v by HI. The overall seroprevalence of anti-H1N1v has risen from 36.9% (95% confidence interval (95%CI), 33-41) in unvaccinated persons after the first wave to 57.3% (95%CI, 53.1-61.2) in vaccinated and unvaccinated. The highest rate of seropositivity was detected in the age group of 10-19 years (66%; 95%CI, 55.8-75.2), whereas the lowest was found in the age group 40-59 years (51%; 95%CI, 40.8-61.1). Although seroprevalence has significantly increased, sufficient herd immunity is still not achieved. Therefore, general vaccination programs have to be propagated continuously by public health authorities.
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Affiliation(s)
- C Reinheimer
- Institute for Medical Virology, University Hospital Frankfurt am Main, Paul-Ehrlich-Straße 40, 60596, Frankfurt am Main, Germany.
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18
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Malik MT, Gumel A, Thompson LH, Strome T, Mahmud SM. "Google flu trends" and emergency department triage data predicted the 2009 pandemic H1N1 waves in Manitoba. Canadian Journal of Public Health 2011. [PMID: 21913587 DOI: 10.1007/bf03404053] [Citation(s) in RCA: 40] [Impact Index Per Article: 3.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 12/01/2022]
Abstract
OBJECTIVES We assessed the performance of syndromic indicators based on Google Flu Trends (GFT) and emergency department (ED) data for the early detection and monitoring of the 2009 H1N1 pandemic waves in Manitoba. METHODS Time-series curves for the weekly counts of laboratory-confirmed H1N1 cases in Manitoba during the 2009 pandemic were plotted against the three syndromic indicators: 1) GFT data, based on flu-related Internet search queries, 2) weekly count of all ED visits triaged as influenza-like illness (ED ILI volume), and 3) percentage of all ED visits that were triaged as an ILI (ED ILI percent). A linear regression model was fitted separately for each indicator and correlations with weekly virologic data were calculated for different lag periods for each pandemic wave. RESULTS All three indicators peaked 1-2 weeks earlier than the epidemic curve of laboratory-confirmed cases. For GFT data, the best-fitting model had about a 2-week lag period in relation to the epidemic curve. Similarly, the best-fitting models for both ED indicators were observed for a time lag of 1-2 weeks. All three indicators performed better as predictors of the virologic time trends during the second wave as compared to the first. There was strong congruence between the time series of the GFT and both the ED ILI volume and the ED ILI percent indicators. CONCLUSION During an influenza season characterized by high levels of disease activity, GFT and ED indicators provided a good indication of weekly counts of laboratory-confirmed influenza cases in Manitoba 1-2 weeks in advance.
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19
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High incidence of severe influenza among individuals over 50 years of age. CLINICAL AND VACCINE IMMUNOLOGY : CVI 2011; 18:1918-24. [PMID: 21900532 DOI: 10.1128/cvi.05357-11] [Citation(s) in RCA: 24] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 01/28/2023]
Abstract
Age-specific epidemiological data on asymptomatic, symptomatic, and severe infections are essential for public health policies on combating influenza. In this study, we incorporated data on microbiologically confirmed infections and seroprevalence to comprehensively describe the epidemiology of pandemic H1N1 2009 influenza. Seroprevalence was determined from 1,795 random serum samples collected in our hospital in January 2007 (before the first wave of the pandemic) and March 2010 (after the second wave). Data on microbiologically confirmed infection and severe cases were obtained from the Centre for Health Protection in Hong Kong. Severe cases were most common in the 51- to 60-year-old age group. The microbiologically confirmed incidence rate was highest for children aged ≤10 years and dropped sharply for the adult population (ρ = -1.0; P < 0.01), but the incidence rate for severe disease was highest for the 51- to 60-year-old age group. For the 51- to 60-year-old age group, the seroprevalence was similar to that for the younger age groups, but the proportion of severe cases relative to seroprevalence was significantly higher than that for 11- to 50-year-old age groups. As judged from the percentage of specimens positive for other respiratory viruses compared with that for pandemic H1N1 virus, the impact of symptomatic disease due to pandemic H1N1 virus was higher than that for other respiratory viruses in people aged ≤50 years. In conclusion, the 51- to 60-year-old age group, which had the highest overall incidence and the highest rate of severe disease but is currently not considered by the World Health Organization to be an at-risk group, should be prioritized for influenza vaccination in areas where universal influenza vaccination is not practiced.
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20
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Effectiveness of the pandemic H1N1 influenza vaccines against laboratory-confirmed H1N1 infections: population-based case-control study. Vaccine 2011; 29:7975-81. [PMID: 21884747 DOI: 10.1016/j.vaccine.2011.08.068] [Citation(s) in RCA: 39] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/03/2011] [Revised: 07/08/2011] [Accepted: 08/14/2011] [Indexed: 11/22/2022]
Abstract
BACKGROUND Excellent immune responses following 1 or 2 doses of the monovalent inactivated pandemic H1N1 vaccines have been documented, but the effectiveness of these vaccines against laboratory-confirmed H1N1 infections in the general population is not clear. We evaluated the effectiveness of the pandemic H1N1 and seasonal trivalent influenza vaccines (TIV) used during the 2009 mass vaccination campaign in Manitoba (Canada) in preventing laboratory-confirmed H1N1 infections. METHODS A population-based case-control study using data from Cadham Provincial Laboratory (CPL) and the Manitoba Immunization Monitoring System (MIMS). All Manitoba residents ≥6 months of age who had a respiratory specimen tested at CPL for H1N1 were included in the study. Cases were individuals who tested positive for pandemic H1N1 influenza A by reverse transcriptase-PCR (N=1435). Controls were individuals who tested negative for both influenza A and B (N=2309). Information on receipt of TIV or H1N1 vaccine was obtained by record linkage with MIMS, the population-based province-wide immunization registry. RESULTS Overall, the adjuvanted H1N1 vaccine was 86% (95%CI 75-93%) effective in preventing laboratory-confirmed H1N1 infections when vaccination occurred ≥14 days before testing. Effectiveness seemed lower among older (≥50 years) individuals [51% (-51 to 84%)] and among those with immunocompromising conditions [67% (-13 to 90%)]. There was also evidence that the H1N1 vaccine might be less effective among those who had received the 2009/10 TIV. DISCUSSION The adjuvanted H1N1 vaccine used during Manitoba's H1N1 mass vaccination campaign was highly effective against laboratory-confirmed pandemic H1N1 infection, especially among children and younger adults.
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21
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Kelly H, Peck HA, Laurie KL, Wu P, Nishiura H, Cowling BJ. The age-specific cumulative incidence of infection with pandemic influenza H1N1 2009 was similar in various countries prior to vaccination. PLoS One 2011; 6:e21828. [PMID: 21850217 PMCID: PMC3151238 DOI: 10.1371/journal.pone.0021828] [Citation(s) in RCA: 69] [Impact Index Per Article: 5.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/03/2011] [Accepted: 06/13/2011] [Indexed: 01/05/2023] Open
Abstract
BACKGROUND During the influenza pandemic of 2009 estimates of symptomatic and asymptomatic infection were needed to guide vaccination policies and inform other control measures. Serological studies are the most reliable way to measure influenza infection independent of symptoms. We reviewed all published serological studies that estimated the cumulative incidence of infection with pandemic influenza H1N1 2009 prior to the initiation of population-based vaccination against the pandemic strain. METHODOLOGY AND PRINCIPAL FINDINGS We searched for studies that estimated the cumulative incidence of pandemic influenza infection in the wider community. We excluded studies that did not include both pre- and post-pandemic serological sampling and studies that included response to vaccination. We identified 47 potentially eligible studies and included 12 of them in the review. Where there had been a significant first wave, the cumulative incidence of pandemic influenza infection was reported in the range 16%-28% in pre-school aged children, 34%-43% in school aged children and 12%-15% in young adults. Only 2%-3% of older adults were infected. The proportion of the entire population infected ranged from 11%-18%. We re-estimated the cumulative incidence to account for the small proportion of infections that may not have been detected by serology, and performed direct age-standardisation to the study population. For those countries where it could be calculated, this suggested a population cumulative incidence in the range 11%-21%. CONCLUSIONS AND SIGNIFICANCE Around the world, the cumulative incidence of infection (which is higher than the cumulative incidence of clinical disease) was below that anticipated prior to the pandemic. Serological studies need to be routine in order to be sufficiently timely to provide support for decisions about vaccination.
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Affiliation(s)
- Heath Kelly
- Victorian Infectious Diseases Reference Laboratory, North Melbourne, Victoria, Australia.
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22
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Sertogullarindan B, Ozbay B, Gunini H, Sunnetcioglu A, Arisoy A, Bilgin HM, Mermit Cilingir B, Duran M, Yildiz H, Ekin S, Baran A. Clinical and prognostic features of patients with pandemic 2009 influenza A (H1N1) virus in the intensive care unit. Afr Health Sci 2011; 11:163-70. [PMID: 21857845 PMCID: PMC3158518] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 05/31/2023] Open
Abstract
OBJECTIVE To investigate the clinical and prognostic features of patients admitted to intensive care unit (ICU) with pandemic 2009 influenza A (H1N1) virus. METHODS Patients admitted to the intensive care unit for severe pneumonia associated with pandemic 2009 influenza A (H1N1) virus were evaluated. RESULTS The study included 20 patients with the mean age of 36±13. Of the 20 subjects, 17 (85%) had underlying conditions. Of the 20 patients, 11(55%) were discharged and 9 (45%) died. Cardinal symptoms were fever, myalgia, and hemoptysis with the rates of 85 %, 75 % and 45 %, respectively. All patients had pneumonic infiltrations in their chest roentgenograms. Main laboratory findings were lymphopenia, high creatin phosphokinase (CPK) and Lactate dehydrogenase (LDH) levels. All patients had positivity on real time reverse transcription-polymerase chain reaction (RT-PCR). None of the patients had pandemic 2009 influenza A (H1N1) virus vaccination. None of them had taken oseltamivir within 48 hours. Main reasons for mortality were cardiovascular complications and ventilatory associated pneumonia due to Acynetobacter baumannii. CONCLUSION Early diagnosis and antiviral treatment in these cases seem to be the best approach to avoid serious illness. Special attention should be given to patients having underlying conditions such as cardiovascular and pulmonary diseases and pregnancy.
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MESH Headings
- Adolescent
- Adult
- Aged
- Antiviral Agents/therapeutic use
- Cause of Death
- Comorbidity
- Female
- Humans
- Influenza A Virus, H1N1 Subtype/isolation & purification
- Influenza, Human/complications
- Influenza, Human/diagnosis
- Influenza, Human/drug therapy
- Influenza, Human/epidemiology
- Influenza, Human/virology
- Intensive Care Units/statistics & numerical data
- Male
- Middle Aged
- Nigeria/epidemiology
- Oseltamivir/therapeutic use
- Pandemics
- Patient Admission/statistics & numerical data
- Pneumonia, Viral/diagnosis
- Pneumonia, Viral/drug therapy
- Pneumonia, Viral/epidemiology
- Pneumonia, Viral/etiology
- Prognosis
- Prospective Studies
- Reverse Transcriptase Polymerase Chain Reaction
- Severity of Illness Index
- Treatment Outcome
- Young Adult
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Affiliation(s)
- B Sertogullarindan
- Department of Pulmonary and Critical Care, Medical Faculty of Yuzuncu Yil University, Van, Turkye.
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23
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Huo X, Qi X, Tang F, Zu R, Li L, Wu B, Qin Y, Ji H, Fu J, Wang S, Tian H, Hu Z, Yang H, Zhou M, Wang H, Zhu F. Seroprevalence of pandemic (H1N1) 2009 in pregnant women in China: an observational study. PLoS One 2011; 6:e17995. [PMID: 21437256 PMCID: PMC3060915 DOI: 10.1371/journal.pone.0017995] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/28/2010] [Accepted: 02/20/2011] [Indexed: 01/05/2023] Open
Abstract
Background We investigated the seropositive rates and persistence of antibody against pandemic (H1N1) 2009 virus (pH1N1) in pregnant women and voluntary blood donors after the second wave of the pandemic in Nanjing, China. Methodology/Principal Findings Serum samples of unvaccinated pregnant women (n = 720) and voluntary blood donors (n = 320) were collected after the second wave of 2009 pandemic in Nanjing. All samples were tested against pH1N1 strain (A/California/7/2009) with hemagglutination inhibition assay. A significant decline in seropositive rates, from above 50% to about 20%, was observed in pregnant women and voluntary blood donors fifteen weeks after the second wave of the pandemic. A quarter of the samples were tested against a seasonal H1N1 strain (A/Brisbane/59/2007). The antibody titers against pH1N1 strain were found to correlate positively with those against seasonal H1N1 strain. The correlation was modest but statistically significant. Conclusions and Significance The high seropositive rates in both pregnant women and voluntary blood donors suggested that the pH1N1 virus had widely spread in these two populations. Immunity derived from natural infection seemed not to be persistent well.
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Affiliation(s)
- Xiang Huo
- Jiangsu Provincial Center for Disease Prevention and Control, Nanjing, China
| | - Xian Qi
- Jiangsu Provincial Center for Disease Prevention and Control, Nanjing, China
| | - Fenyang Tang
- Jiangsu Provincial Center for Disease Prevention and Control, Nanjing, China
| | - Rongqiang Zu
- Jiangsu Provincial Center for Disease Prevention and Control, Nanjing, China
| | - Liang Li
- Jiangsu Provincial Center for Disease Prevention and Control, Nanjing, China
| | - Bin Wu
- Jiangsu Provincial Center for Disease Prevention and Control, Nanjing, China
| | - Yuanfang Qin
- Jiangsu Provincial Center for Disease Prevention and Control, Nanjing, China
| | - Hong Ji
- Jiangsu Provincial Center for Disease Prevention and Control, Nanjing, China
| | - Jianguang Fu
- Jiangsu Provincial Center for Disease Prevention and Control, Nanjing, China
| | - Shenjiao Wang
- Jiangsu Provincial Center for Disease Prevention and Control, Nanjing, China
| | - Hua Tian
- Jiangsu Provincial Center for Disease Prevention and Control, Nanjing, China
| | - Zhibin Hu
- College of Public Health, Nanjing Medical University, Nanjing, China
| | - Haitao Yang
- Jiangsu Provincial Center for Disease Prevention and Control, Nanjing, China
| | - Minghao Zhou
- Jiangsu Provincial Center for Disease Prevention and Control, Nanjing, China
| | - Hua Wang
- Jiangsu Provincial Center for Disease Prevention and Control, Nanjing, China
| | - Fengcai Zhu
- Jiangsu Provincial Center for Disease Prevention and Control, Nanjing, China
- * E-mail:
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