Volume 16, Number 11—November 2010
Estimates of the True Number of Cases of Pandemic (H1N1) 2009, Beijing, China
|A||Proportion of symptomatic infection among case-patients with pandemic (H1N1) 2009||70–75||Pandemic (H1N1) 2009, ECDC Risk Assessment.,2009; version 6, 6 Nov.|
|B||Proportion of ILI among symptomatic case-patients with pandemic (H1N1) 2009||26–42||Literature and unpublished clinical data|
|C1 (period 2a)||Consultation rate among ILI case-patients in secondary and tertiary hospitals||38||Telephone interview conducted by Beijing CDC|
|C2 (period 2b)||Consultation rate among ILI case-patients in secondary and tertiary hospitals||48||Telephone interview conducted by Beijing CDC|
|D||Sampling success rate||80–90||Previous surveillance data|
|E||Sensitivity of test||95–100||Professional recommendations|
*ECDC, European Centre for Disease Prevention and Control; ILI, influenza-like illness; Beijing CDC, Beijing Center for Disease Prevention and Control.
†The multiplier model was only used for phase 2 in this study, and phase 2 was divided into 2 periods, period 2a and period 2b. During phase 2, the true number of infections was calculated by multiplying the baseline by the estimation coefficient, using the multiplier model. The baseline case number was equal to the sum of product of weekly ILIs number in level 2/3 hospitals and the corresponding weekly pandemic (H1N1) 2009 positive rate among case-patients with ILIs. The estimation coefficient was obtained by multiplying the reciprocal of the parameters mentioned in this table.
The baseline case numbers in periods 2a and 2b were 6,520 and 171,899, respectively.