Abstract
BackgroundHigher incidence of and risk of hospitalisation and death from Influenza A(H1N1)pdm09 during the 2009 pandemic was reported in ethnic minority groups in many high-income settings including in the United Kingdom (UK). Many of these studies rely on geographical and temporal aggregation of cases and can be difficult to interpret due to the spatial and temporal factors in outbreak spread. Further, it can be challenging to distinguish between disparities in health outcomes caused by variation in transmission risk or disease severity.MethodsWe used anonymised laboratory confirmed and suspected case data, classified by ethnicity and deprivation status, to evaluate how disparities in risk between socio-economic and ethnic groups vary over the early stages of the 2009 Influenza A(H1N1)pdm09 epidemic in Birmingham and London, two key cities in the emergence of the UK epidemic. We evaluated the relative risk of infection in key ethnic minority groups and by national and city level deprivation rank.ResultsWe calculated higher incidence in more deprived areas and in people of South Asian ethnicity in both Birmingham and London, although the magnitude of these disparities reduced with time. The clearest disparities existed in school-aged children in Birmingham, where the most deprived fifth of the population was 2.8 times more likely to be infected than the most affluent fifth of the population.ConclusionsOur analysis shows that although disparities in reported cases were present in the early phase of the Influenza A(H1N1)pdm09 outbreak in both Birmingham and London, they vary substantially depending on the period over which they are measured. Further, the development of disparities suggest that clustering of social groups play a key part as the outbreak appears to move from one ethnic and socio-demographic group to another. Finally, high incidence and large disparities between children indicate that they may hold an important role in driving inequalities.
Highlights
Higher incidence of and risk of hospitalisation and death from Influenza A(H1N1)pdm09 during the 2009 pandemic was reported in ethnic minority groups in many high-income settings including in the United Kingdom (UK)
Evaluating the bias of missing data showed no strong correlation between missing postcode information and any variable used in the analysis (Additional file 1)
By analysing individual level data of cases reported during the initial phase of the UK Influenza A(H1N1)pdm09 (pH1N1) epidemic in two urban settings we found that disparities between socio-economic and ethnic groups were clear at the beginning of the local outbreaks in both cities, but much greater in Birmingham than London
Summary
Higher incidence of and risk of hospitalisation and death from Influenza A(H1N1)pdm during the 2009 pandemic was reported in ethnic minority groups in many high-income settings including in the United Kingdom (UK). Many of these studies rely on geographical and temporal aggregation of cases and can be difficult to interpret due to the spatial and temporal factors in outbreak spread. Clear measurement of disparity in risk of acquisition of infection requires accurate, detailed data on cases at the point of infection Without such data, analyses rely on proxy measures of infection such as hospitalisation or mortality [5, 7, 10, 11], where reported rates can be influenced by many factors not associated with transmission. By aggregating data with low spatial resolution, apparent associations between risk and social factors can become exacerbated or diluted due to confounding from geographical variation in infection risk within regions
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