Analysis of epidemiological features and risk factors of severe cases and deaths of pandemic influenza A (H1N1) 2009 in Beijing / 中华传染病杂志

ABSTRACT

Objective To describe the epidemiological features of severe cases and deaths of pandemic influenza A (H1N1) 2009 in Beijing and to explore the main risk factors associated with the disease severity. Methods Data of pandemic influenza A (H1N1) 2009 reported in Beijing were collected and analyzed. The relative risks between disease condition and possible risk factors were determined using the multi-factor Logistic regression analysis. Results The incidence of pandemic influenza A(H1N1) 2009 was 66. 1/100 000, and the highest incidence was 86. 8/100 000 which occurred among people aged 25-60 years old. The prevalence of critical patients (12. 5/100 000 and 3.9/100 000, respectively), mortality (0. 9/100 000 and 0. 7/100 000, respectively) and fatality (2.4 % and 3.3 %, respectively) in people aged 0-5 years old and above 60 years old were higher than other age groups. There were 110 (20. 0%) preschool children among 549 critical cases, which were the largest proportion of critical cases. Among 69 death cases, 17 (24. 6%) were retirees with the highest proportion of death cases. More than 70. 0% of the critical cases and deaths visited hospital within two days of onset. The chronic heart disease and chronic lung disease were the most frequent risk factors of severe and death cases. Multi-factor Logistic regression analysis showed that the variables including aged above 60 years old (OR = 3. 586, 95 % CI = 1. 586 - 8. 117), chronic heart disease (OR=2. 126, 95%CI= 1. 178-3. 835), and chronic lung disease (OR=1. 954, 95%CI=1. 126-3. 391) were significantly associated with the disease severity. Conclusion Factors of aged above 60 years older, chronic heart disease and chronic lung disease may aggravate the severity of influenza A (H1N1).