Patterns of early transmission of pandemic influenza in London - link with deprivation.

BACKGROUND

During the early containment phase in England from April to June 2009, the national strategy for H1N1 pandemic influenza involved case investigation and treatment, and tracing and prophylaxis of contacts.

OBJECTIVE

To describe the relationship between early transmission of H1N1 pandemic influenza in London and age and socio-economic status.

METHODS

Epidemiological data on cases of pandemic flu in London reported to the London Flu Response Centre were analysed to determine patterns of transmission.

RESULTS

There were 3487 reported cases (2202 confirmed, 1272 presumed and 14 probable) from 20 April to 28 June 2009, during the 'containment' period. The highest report rate of 206 per 100 000 (95% CI 195-218) was seen in primary school-age children (5-11 years) followed by 129 (95% CI 119-139) in secondary school-age children (12-18 years). Reports of cases were initially concentrated in affluent areas but overall showed a clear trend with deprivation and risk ratio of 2·32 (95% CI 1·94-2·78) between the most deprived and the least deprived.

CONCLUSION

Early transmissions were highest amongst school-aged children but linked with socio-economic deprivation across all age groups.