Epidemiological Characteristics and Underlying Risk Factors for Mortality during the Autumn 2009 Pandemic Wave in Mexico

Abstract

BackgroundElucidating the role of the underlying risk factors for severe outcomes of the 2009 A/H1N1 influenza pandemic could be crucial to define priority risk groups in resource-limited settings in future pandemics.MethodsWe use individual-level clinical data on a large series of ARI (acute respiratory infection) hospitalizations from a prospective surveillance system of the Mexican Social Security medical system to analyze clinical features at presentation, admission delays, selected comorbidities and receipt of seasonal vaccine on the risk of A/H1N1-related death. We considered ARI hospitalizations and inpatient-deaths, and recorded demographic, geographic, and medical information on individual patients during August-December, 2009.ResultsSeasonal influenza vaccination was associated with a reduced risk of death among A/H1N1 inpatients (OR = 0.43 (95% CI: 0.25, 0.74)) after adjustment for age, gender, geography, antiviral treatment, admission delays, comorbidities and medical conditions. However, this result should be interpreted with caution as it could have been affected by factors not directly measured in our study. Moreover, the effect of antiviral treatment against A/H1N1 inpatient death did not reach statistical significance (OR = 0.56 (95% CI: 0.29, 1.10)) probably because only 8.9% of A/H1N1 inpatients received antiviral treatment. Moreover, diabetes (OR = 1.6) and immune suppression (OR = 2.3) were statistically significant risk factors for death whereas asthmatic persons (OR = 0.3) or pregnant women (OR = 0.4) experienced a reduced fatality rate among A/H1N1 inpatients. We also observed an increased risk of death among A/H1N1 inpatients with admission delays >2 days after symptom onset (OR = 2.7). Similar associations were also observed for A/H1N1-negative inpatients.ConclusionsGeographical variation in identified medical risk factors including prevalence of diabetes and immune suppression may in part explain between-country differences in pandemic mortality burden. Furthermore, access to care including hospitalization without delay and antiviral treatment and are also important factors, as well as vaccination coverage with the 2008–09 trivalent inactivated influenza vaccine.

Risk Factors for Mortality among 2009 A/H1N1 Influenza Hospitalizations in Maricopa County, Arizona, April 2009 to March 2010

“…In line with previous studies [16–19], immunosuppression (OR = 4.5 (95% CI: 2.1, 9.7)) was a significant risk factor of mortality among A/H1N1 inpatients in an adjusted multivariate logistic regression analysis. Similarly, chronic lung disease (OR = 3.5) and cancer within the last 12 months (OR = 4.3) were associated with an increase risk of death among A/H1N1 inpatients, which is also in agreement with previous studies [15, 17, 20].…”

Comparison of severely ill patients with influenza A(H1N1)pdm09 infection during the pandemic and post-pandemic periods in Singapore

“…1 shows the temporal distribution of severely ill patients with laboratory confirmed influenza A(H1N1)pdm09 infection admitted to hospitals and the average daily number of attendances for ARI at government primary care clinics from epidemiological week (Eweek) 23 (7)(8)(9)(10)(11)(12)(13) in 2009 to E-week 32 (6)(7)(8)(9)(10)(11)(12) in 2010. In 2009, a steady increase in attendances for ARI was observed from E-week 25 (21)(22)(23)(24)(25)(26)(27) onwards, which peaked in E-week 30 (26 July-1 August), and decreased over the subsequent weeks until E-week 36 (6)(7)(8)(9)(10)(11)(12).…”

“…Temperate countries such as Germany, Greece, Spain, England, Canada and Mexico, observed a second wave of patients with influenza A(H1N1)pdm09 infection during their post-pandemic period or post-pandemic influenza season [10][11][12][13][14][20][21][22]. A study conducted in England reported a greater burden of severe illness with more deaths, more critical care admissions and more hospital admissions due to influenza A(H1N1)pdm09 in the second year of its circulation than in the pandemic year [23].…”

Anxiety and Work Avoidance among Intensive Care Workers during an Influenza A/H1N1 Outbreak

“…The global influenza A/H1N1 (H1N1) pandemic in 2009 was associated with high morbidity and mortality [1,2]. Healthcare workers (HCWs) are identified as being at high-risk of being infected with influenza A/H1N1 during such epidemics [3,4].…”