Risk factors for severe outcome of cases with pandemic influenza A(H1N1)pdm09

The aim of this study is to describe demographic, clinical and epidemiological characteristics of cases with laboratory-confirmed pandemic influenza virus A(H1N1)pdm09 reported in Slovakia from May 28, 2009 to December 30, 2009 and analyse the association between risk factors and severe outcome of these cases.

In the spring of 2009, an outbreak of a pandemic influenza virus A(H1N1)pdm09, emerged in Mexico and spread globally. Until December 2009, 1,014 cases were notified in Slovakia.

The data were collected within national influenza surveillance system. Odds ratios (95% CI) were calculated. Associations were found to be significantly associated with the worse outcome (p < 0.05) in the univariate analysis and were adjusted for possible effects of age and sex by using a logistic regression model.

Out of the total number of 1,014 cases, 131 (12.9 %) cases were hospitalized, and 43 (4.2 %) of those were admitted to intensive care units. During the reporting period, 38 deaths were reported, representing a case fatality rate of 3.75 %. The median age of severe cases (35 years, IQR = 29 y) was significantly higher than the median age of mild cases (24 years, IQR = 19 y; p < 0.001). By using a logistic regression, we found out that chronic obstructive pulmonary disease (COPD) (aOR = 9.2; 95%CI: 1.42-59.98), cardiovascular diseases (aOR = 14.97; 95%CI: 5.49-40.79), malignity (aOR = 7.6; 95%CI: 1.95-29.37) and gravidity (aOR = 55.21; 95% CI: 14.40-211.58) were significantly associated with severe outcomes of the cases.

The fact, that 35% of severely ill patients did not report any risk factor suggests the importance of vaccination as a prevention of influenza (Tab. 2, Fig. 1, Ref. 18). Text in PDF www.elis.sk.