Pandemic influenza A (H1N1) 2009 in Madrid, Spain: incidence and characteristics in immigrant and native population

Abstract

Some immigrants and refugees might be more vulnerable than other groups to pandemic influenza because of pre-existing health and social disparities, migration history and living conditions. The objective of this study was to compare, between the immigrant and autochtonous population, the incidence and characteristics of influenza cases consulting in primary care (PC) and severe influenza cases. Descriptive cross-sectional study of influenza episodes registered in PC and severe influenza cases reported between 1 May 2009 and 22 May 2010, by gender and origin. Age-adjusted rates were calculated and the association between origin and chronic pathology, pregnancy, delay in admission to hospital and admission to intensive care units (ICU) was analyzed by logistic regression and generalized linear models. The influenza rate in PC, adjusted by age, was lower for immigrant population (2396.3, 95% confidence interval (95% CI) 2362.5-2430.0 vs. 2795.9, 95% CI 2780.4-2811.5 per 100, 000). The difference between severe influenza rates by origin was not statistically significant. Chronic conditions were less common in immigrant population. In severe influenza cases, pregnancy was more common in immigrant women, and the probability of admission to ICU was higher in men from Central and Eastern Europe (prevalence ratio (PR) 8.44, 95% CI 2.81-25.40) and North African women (PR 3.30, 95% CI 1.09-10.05). Differences in influenza rates were detected by origin. This information could be useful for new pandemic wave management purposes, in addition to targetting future investigations. Pandemic influenza preparedness and response plans should incorporate specific actions to improve immigrants' access to health services and to decrease cultural barriers.