2014.ISDS.Abstracts.Final.pdf


ISDS Annual Conference Proceedings 2014. This is an Open Access article distributed under the terms of the Creative Commons Attribution-
Noncommercial 3.0 Unported License (http://creativecommons.org/licenses/by-nc/3.0/), permitting all non-commercial use, distribution, 
and reproduction in any medium, provided the original work is properly cited.

ISDS 2014 Conference Abstracts

Temporal Association between ILI and the Winter 
Holiday Break, U.S. 2004-2012

Hongjiang Gao*, Yenlik Zheteyeva, Karen Wong, JianRong Shi, Amra Uzicanin and Rainy 
Jeanette

US CDC, Atlanta, GA, USA

Objective
To explore the relationship between influenza-like illness observed 

by influenza out-patient network and winter holiday breaks in US.

Introduction
Decreasing contact between infectious and susceptible people in 

community settings may reduce influenza transmission. Examining 
the temporal relationship between the winter holiday break and 
seasonal influenza activity can provide insight of alternative contact 
patterns on influenza spread.

Methods
We examined weekly influenza-like illness (ILI) rates by HHS 

region in the United States from 2003–2014. We used time series 
analyses to compare observed and predicted ILI rates for the last week 
of each year and the first week of each new year using the Auto-
Regressive Integrated Moving Average method.

Results
Most (72/90; 80%) observed ILI rates for the last week of the year 

were higher than predicted, and 12 among these 72 were even higher 
than the upper bound of 95% prediction interval. In contrast, most 
(76/90; 84%) observed ILI rates for the first week of the year were 
lower than predicted, with 14 out of 76 lower than the lower bound of 
95% prediction interval.

Conclusions
Most frequently, the last week in December had higher observed 

than predicted ILI rates, and the first week of January had lower 
observed than predicted ILI rates. Further research is needed to 
determine whether these observed differences are due to changes in 
social mixing patterns or in other factors, such as healthcare-seeking 
behavior.

Keywords
influenza; time series; winter holiday breaks

*Hongjiang Gao

E-mail: uxi7@cdc.gov    

Online Journal of Public Health Informatics * ISSN 1947-2579 * http://ojphi.org * 7(1):e75, 2015