Risk Factors for Severe Illness with 2009 Pandemic Influenza A (H1N1) Virus Infection in China

Office for Disease Control and Emergency Response, National Institute forViral Disease Control and Prevention, Chinese Center for Disease Control and Prevention, Beijing, China.
Clinical Infectious Diseases (Impact Factor: 8.89). 02/2011; 52(4):457-65. DOI: 10.1093/cid/ciq144
Source: PubMed


Data on risk factors for severe outcomes from 2009 pandemic influenza A (H1N1) virus infection are limited outside of developed countries.
We reviewed medical charts to collect data from patients hospitalized with laboratory-confirmed 2009 H1N1 infection who were identified across China during the period from September 2009 through February 2010, and we analyzed potential risk factors associated with severe illness (defined as illness requiring intensive care unit admission or resulting in death).
Among 9966 case patients, the prevalence of chronic medical conditions (33% vs 14%), pregnancy (15% vs 7%), or obesity (19% vs 14%) was significantly higher in those patients with severe illness than it was in those with less severe disease. In multivariable analyses, among nonpregnant case patients aged ≥ 2 years, having a chronic medical condition significantly increased the risk of severe outcome among all age groups, and obesity was a risk factor among those <60 years of age. The risk of severe illness among pregnant case patients was significantly higher for those in the second and third trimesters. The risk of severe illness was increased when oseltamivir treatment was initiated ≥ 5 days after illness onset (odds ratio, 1.42; 95% confidence interval, 1.20-1.67). For persons <60 years of age, the prevalence of obesity among case patients with severe illness was significantly greater than it was among those without severe illness or among the general population.
Risk factors for severe 2009 H1N1 illness in China were similar to those observed in developed countries, but there was a lower prevalence of chronic medical conditions and a lower prevalence of obesity. Obesity was a risk factor among case patients < 60 years of age. Early initiation of oseltamivir treatment was most beneficial, and there was an increased risk of severe disease when treatment was started ≥ 5 days after illness onset.

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    • "According to the guidelines released based on recommendations from the World Health Organization (WHO) and Centers for Disease Control and Prevention (CDC), treatment is warranted for all hospitalized patients, and for confirmed and probable outpatient cases. Treatment should ideally be initiated within 48 h of the onset of illness as it has been shown to reduce disease severity as well as mortality (Jain et al., 2009; Siston et al., 2010; Hiba et al., 2011; Kumar, 2011; Rodríguez et al., 2011; Yu et al., 2011; Chemaly et al., 2012; Hsu et al., 2012; Louie et al., 2012; Muthuri et al., 2013). However, treatment should be initiated even if 48 h has lapsed. "
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    ABSTRACT: The novel avian influenza A H7N9 virus which caused the first human infection in Shanghai, China; was reported on the 31st of March 2013 before spreading rapidly to other Chinese provinces and municipal cities. This is the first time the low pathogenic avian influenza A virus has caused human infections and deaths; with cases of severe respiratory disease with pneumonia being reported. There were 440 confirmed cases with 122 fatalities by 16 May 2014; with a fatality risk of ∼28%.The median age of patients was 61 years with a male-to-female ratio of 2.4:1. The main source of infection was identified as exposure to poultry and there is so far no definitive evidence of sustained person-to-person transmission. The neuraminidase inhibitors, namely oseltamivir, zanamivir, and peramivir; have shown good efficacy in the management of the novel H7N9 virus. Treatment is recommended for all hospitalized patients, and for confirmed and probable outpatient cases; and should ideally be initiated within 48 h of the onset of illness for the best outcome. Phylogenetic analysis found that the novel H7N9 virus is avian in origin and evolved from multiple reassortments of at least four origins. Indeed the novel H7N9 virus acquired human adaptation via mutations in its eight RNA gene segments. Enhanced surveillance and effective global control are essential to prevent pandemic outbreaks of the novel H7N9 virus.
    Frontiers in Microbiology 03/2015; 6(140):1-11. DOI:10.3389/fmicb.2015.00140 · 3.99 Impact Factor
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    • "Early use of oseltamivir was reported to be beneficial in treatment [8,10,21,22]. Furthermore, it was reported that among the patients with A(H1N1)pdm09 infection, early use of antiviral therapy prevented development of pneumonia [23,24]. We found that the patients who received neuraminidase inhibitors within 2 days after the disease onset were found to be less likely to die in comparison with the patients who received neuraminidase inhibitors later than two days (Odds ratio: 0.16, confidence interval: 0.03-0.74, "
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    ABSTRACT: Background: The fatality attributed to pandemic influenza A H1N1 was not clear in the literature. We described the predictors for fatality related to pandemic influenza A H1N1 infection among hospitalized adult patients. Methods: This is a multicenter study performed during the pandemic influenza A H1N1 [A(H1N1)pdm09] outbreak which occurred in 2009 and 2010. Analysis was performed among laboratory confirmed patients. Multivariate analysis was performed for the predictors of fatality. Results: In the second wave of the pandemic, 848 adult patients were hospitalized because of suspected influenza, 45 out of 848 (5.3%) died, with 75% of fatalities occurring within the first 2 weeks of hospitalization. Among the 241 laboratory confirmed A(H1N1)pdm09 patients, the case fatality rate was 9%. In a multivariate logistic regression model that was performed for the fatalities within 14 days after admission, early use of neuraminidase inhibitors was found to be protective (Odds ratio: 0.17, confidence interval: 0.03-0.77, p=0.022), nosocomial infections (OR: 5.7, CI: 1.84-18, p=0.013), presence of malignant disease (OR: 3.8, CI: 0.66-22.01, p=0.133) significantly increased the likelihood of fatality. Conclusions: Early detection of the infection, allowing opportunity for the early use of neuraminidase inhibitors, was found to be important for prevention of fatality. Nosocomial bacterial infections and underlying malignant diseases increased the rate of fatality.
    BMC Infectious Diseases 06/2014; 14(1):317. DOI:10.1186/1471-2334-14-317 · 2.61 Impact Factor
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    • "However, comparisons must be treated with caution, especially with clinical signs, as diagnostic criteria used by physicians could have varied across studies. The results of this study are also in line with previous ones showing that AH1N1 infection was not sex specific [28-30]. "
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    ABSTRACT: Background In 2009 a new influenza serotype (AH1N1) was identified in Mexico that spread rapidly generating worldwide alarm. San Luis Potosi (SLP) was the third state with more cases reported in that year. The clinical identification of this flu posed a challenge to medical staff. This study aimed at estimating the AH1N1 infection, hospitalization and mortality rates, and at identifying related clinical features in persons who received medical care during the influenza pandemic. Methods Retrospective study with persons with flu-like illness who received public or private medical care in SLP from 15.03.09 to 30.10.09. Physicians purposely recorded many clinical variables. Samples from pharyngeal exudate or bronchoalveolar lavage were taken to diagnose AH1N1 using real-time PCR. Clinical predictors were identified using multivariate logistic regression with infection as a dependent variable. Odds ratios (OR) with 95% confidence intervals (CI) were computed. Analyses were stratified by age group based on the distribution of positive cases. Results From the 6922 persons with flu symptoms 6158 had available laboratory results from which 44.9% turned out to be positive for AH1N1. From those, 5.8% were hospitalized and 0.7% died. Most positive cases were aged 5–14 years and, in this subgroup, older age was positively associated with A H1N1 infection (95% CI 1.05-1.1); conversely, in patients aged 15 years or more, older age was negatively associated with the infection (95% CI 0.97-0.98). Fever was related in those aged 15 years or more (95% CI 1.4-3.5), and headache (95% CI 1.2-2.2) only in the 0–14 years group. Clear rhinorrhea and cough were positively related in both groups (p < 0.05). Arthralgia, dyspnea and vaccination history were related to lesser risk in persons aged 15 years or more, just as dyspnea, purulent rhinorrhea and leukocytosis were in the 0–14 years group. Conclusion This study identified various signs and symptoms for the clinical diagnosis of AH1N1 influenza and revealed that some of them can be age-specific.
    BMC Infectious Diseases 12/2012; 12(1):363. DOI:10.1186/1471-2334-12-363 · 2.61 Impact Factor
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