title: The Effectiveness of Age-Specific Isolation Policies on Epidemics of Influenza A (H1N1) in a Large City in Central South China.
abstract: During the early stage of a pandemic, isolation is the most effective means of controlling transmission. However, the effectiveness of age-specific isolation policies is not clear; especially little information is available concerning their effectiveness in China. Epidemiological and serological survey data in the city of Changsha were employed to estimate key model parameters. The average infectious period (date of recovery-date of symptom onset) of influenza A (H1N1) was 5.2 days. Of all infected persons, 45.93% were asymptomatic. The basic reproduction number of the influenza A (H1N1) pandemic was 1.82. Based on the natural history of influenza A (H1N1), we built an extended susceptible-exposed-infectious/asymptomatic-removed model, taking age groups: 0-5, 6-14, 15-24, 25-59, and ≥60 years into consideration for isolation. Without interventions, the total attack rates (TARs) in each age group were 42.73%, 41.95%, 20.51%, 45.03%, and 37.49%, respectively. Although the isolation of 25-59 years-old persons was the most effective, the TAR of individuals of aged 0-5 and 6-14 could not be reduced. Paradoxically, isolating individuals ≥60 year olds was not predicted to be an effective way of reducing the TAR in this group but isolating the age-group 25-59 did, which implies inter-age-group transmission from the latter to the former is significant. Isolating multiple age groups increased effectiveness. The most effective combined isolation target groups were of 6-14 + 25-59 year olds, 6-14 + 15-24 + 25-59 year olds, and 0-5 + 6-14 + 25-59 + ≥60 year olds. The last of these isolation schemas reduced the TAR of the total population from 39.64% to 0.006%, which was exceptionally close to the effectiveness of isolating all five age groups (TAR = 0.004%).
authors.affiliation: Office for Disease Control and Emergency Response, Changsha Center for Disease Control and Prevention, Changsha, The People's Republic of China.
authors.forename: Ruchun
authors.initials: R
authors.lastname: Liu
authors.affiliation: Office for Disease Control and Emergency Response, Changsha Center for Disease Control and Prevention, Changsha, The People's Republic of China; Stanley Ho Centre for Emerging Infectious Diseases, The Chinese University of Hong Kong, Shatin, New Territories, Hong Kong SAR, The People's Republic of China.
authors.forename: Ross Ka-kit
authors.initials: RK
authors.lastname: Leung
authors.affiliation: Office for Disease Control and Emergency Response, Changsha Center for Disease Control and Prevention, Changsha, The People's Republic of China.
authors.forename: Tianmu
authors.initials: T
authors.lastname: Chen
authors.affiliation: Office for Disease Control and Emergency Response, Changsha Center for Disease Control and Prevention, Changsha, The People's Republic of China.
authors.forename: Xixing
authors.initials: X
authors.lastname: Zhang
authors.affiliation: Office for Disease Control and Emergency Response, Changsha Center for Disease Control and Prevention, Changsha, The People's Republic of China.
authors.forename: Faming
authors.initials: F
authors.lastname: Chen
authors.affiliation: Office for Disease Control and Emergency Response, Changsha Center for Disease Control and Prevention, Changsha, The People's Republic of China.
authors.forename: Shuilian
authors.initials: S
authors.lastname: Chen
authors.affiliation: Office for Disease Control and Emergency Response, Changsha Center for Disease Control and Prevention, Changsha, The People's Republic of China.
authors.forename: Jin
authors.initials: J
authors.lastname: Zhao
mesh_terms: D000293:Adolescent; D000328:Adult; D000367:Age Factors; D002648:Child; D002675:Child, Preschool; D002681:China / Q000453:epidemiology; D002947:Cities / Q000706:statistics & numerical data*; D003198:Computer Simulation; D006801:Humans; D007223:Infant; D007231:Infant, Newborn; D053118:Influenza A Virus, H1N1 Subtype / Q000502:physiology; D007251:Influenza, Human / Q000453:epidemiology* / Q000821:virology*; D008875:Middle Aged; D010356:Patient Isolation; D011156:Population Density; D011795:Surveys and Questionnaires; D013997:Time Factors; D055815:Young Adult