Household transmission of 2009 influenza A (H1N1) virus after a school-based outbreak in New York City, April-May 2009.
In April 2009, an outbreak due to infection with the 2009 pandemic influenza A (H1N1) virus (pH1N1) was investigated in a New York City high school. We surveyed household contacts of ill students to characterize the extent of transmission within households, identify contact groups at highest risk for illness, and assess the potential for preventing household transmission. Influenza-like illness (ILI) was reported by 79 of 702 household contacts (11.3% attack rate). Multivariate analysis showed that older age was protective: for each increasing year of age, the risk of ILI was reduced 5%. Additional protective factors included antiviral prophylaxis and having had a household discussion about influenza. Providing care for the index case patient and watching television with the index case patient were risk factors among parents and siblings, respectively. Fifty percent of cases occurred within 3 days of onset of illness in the student. These factors have implications for mitigating the impact of pH1N1 transmission.
France
Anne Marie
AM
Epidemic Intelligence Service, Office of Workforce and Career Development, Centers for Disease Control and Prevention, Atlanta, Georgia, USA. afrance@health.nyc.gov
Jackson
Michael
M
Schrag
Stephanie
S
Lynch
Michael
M
Zimmerman
Christopher
C
Biggerstaff
Matthew
M
Hadler
James
J
D000293:Adolescent; D000328:Adult; D002648:Child; D002675:Child, Preschool; D004196:Disease Outbreaks / Q000706:statistics & numerical data*; D005191:Family Characteristics; D005192:Family Health; D005260:Female; D006801:Humans; D007223:Infant; D053118:Influenza A Virus, H1N1 Subtype / Q000302:isolation & purification*; D007251:Influenza, Human / Q000453:epidemiology / Q000635:transmission*; D008297:Male; D008875:Middle Aged; D015999:Multivariate Analysis; D009519:New York City / Q000453:epidemiology; D012307:Risk Factors; D012574:Schools; D011795:Surveys and Questionnaires