The effect of school dismissal on rates of influenza-like illness in New York City schools during the spring 2009 novel H1N1 outbreak.
BACKGROUND
The effects of individual school dismissal on influenza transmission have not been well studied. During the spring 2009 novel H1N1 outbreak, New York City implemented an individual school dismissal policy intended to limit influenza transmission at schools with high rates of influenza-like illness (ILI).


METHODS
Active disease surveillance data collected by the New York City Health Department on rates of ILI in schools were used to evaluate the impact. Sixty-four schools that met the Health Department's criteria for considering dismissal were included in the analysis. Twenty-four schools that met criteria subsequently dismissed all classes for approximately 1 school week. A regression model was fit to these data, estimating the effect of school dismissal on rates of in-school ILI following reconvening, adjusting for potential confounders.


RESULTS
The model estimated that, on average, school dismissal reduced the rate of ILI by 7.1% over the entire average outbreak period. However, a large proportion of in-school ILI occurred before dismissal criteria were met. A separate model estimated that school absenteeism rates were not significantly affected by dismissal.


CONCLUSIONS
Results suggest that individual school dismissal could be considered in situations where schools have a disproportionate number of high-risk students or may be unable to implement recommended preventive or infection control measures. Future work should focus on developing more sensitive indicators of early outbreak detection in schools and evaluating the impact of school dismissal on community transmission.
SciMetrika, LLC, Durham, NC 27713, USA. jegger@scimetrika.com
Joseph R
JR
Egger
Kevin J
KJ
Konty
Elisha
E
Wilson
Adam
A
Karpati
Thomas
T
Matte
Don
D
Weiss
Oxiris
O
Barbot
D000041:Absenteeism; D000293:Adolescent; D002648:Child; D002669:Child Welfare / Q000706:statistics & numerical data; D004196:Disease Outbreaks / Q000517:prevention & control / Q000706:statistics & numerical data*; D006801:Humans; D017053:Infection Control / Q000458:organization & administration*; D053118:Influenza A Virus, H1N1 Subtype; D007251:Influenza, Human / Q000453:epidemiology*; D009519:New York City / Q000453:epidemiology; D012044:Regression Analysis; D012307:Risk Factors; D012572:School Health Services / Q000458:organization & administration; D012574:Schools / Q000458:organization & administration; D013334:Students / Q000706:statistics & numerical data; D014505:Urban Population / Q000706:statistics & numerical data*