The LANCET
Comparative community burden and severity of seasonal and pandemic influenza: results of the Flu Watch cohort study
抜粋
Findings
Based on four-fold titre rises in strain-specific serology, on average influenza infected 18% (95% CI 16–22) of unvaccinated people each winter. Of those infected there were 69 respiratory illnesses per 100 person-influenza-seasons compared with 44 per 100 in those not infected with influenza. The age-adjusted attributable rate of illness if infected was 23 illnesses per 100 person-seasons (13–34), suggesting most influenza infections are asymptomatic. 25% (18–35) of all people with serologically confirmed infections had PCR-confirmed disease. 17% (10–26) of people with PCR-confirmed influenza had medically attended illness. These figures did not differ significantly when comparing pandemic with seasonal influenza. Of PCR-confirmed cases, people infected with the 2009 pandemic strain had markedly less severe symptoms than those infected with seasonal H3N2.