Overrepresentation of South Asian ethnic groups among cases of influenza A(H1N1)pdm09 during the first phase of the 2009 pandemic in England

BACKGROUND: During the first wave of the influenza A(H1N1)pdm09 pandemic in England in 2009, morbidity and mortality were higher in patients of South Asian (Indian, Pakistani or Bangladeshi) ethnic minority groups. OBJECTIVES: This study aims to provide insights in the representation of this group among reported cases, indicating susceptibility and exposure. METHODS: All laboratory-confirmed cases including basic demographic and limited clinical information that were reported to the FluZone surveillance system between April and October 2009 were retrieved. Missing ethnicity data were imputed using the previously developed and validated South Asian Names and Group Recognition Algorithm (SANGRA). Differences between ethnic groups were calculated using chi-square, log-rank and t tests and rate ratios. Geographic clustering was compared using Ripley's K functions. RESULTS: SANGRA identified 2447 (28%) of the total of 8748 reported cases as South Asian. South Asian cases were younger (P