Date of Award

Spring 5-12-2017

Degree Type

Thesis

Degree Name

Master of Public Health (MPH)

Department

Public Health

First Advisor

Dr. Gerardo Chowell

Second Advisor

Dr. Matthew Magee

Abstract

Background:

Seasonal influenza epidemics occur annually in the United States (U.S.) and result in lost workforce productivity, strained healthcare services, and an annual economic burden of $11 billion. While the U.S. has a comprehensive surveillance system, and the Centers for Disease Control and Prevention (CDC) publishes weekly updates on the outlook of seasonal influenza activity (FluView), there is a lack of literature analyzing seasonal influenza peak trends across and within regions of the country over multiple flu seasons. This study aimed to identify trends over time (2005-2015) in the timing and size of seasonal flu outbreak peaks, both across and within Health and Human Services regions.

Methods:

Secondary data analysis was conducted on U.S. national influenza surveillance data compiled and provided by the CDC. The study includes all persons in the United States (all 50 states, District of Columbia, Puerto Rico, and the U.S. Virgin Islands) who sought healthcare for influenza-like illness (ILI) during the 2005-06 flu season through the 2014-15 season. Trends over time in peak timing and size were assessed overall (across all HHS regions) and within regions. The effect of the dominant subtype of influenza virus circulating on peak timing and size was also assessed.

Results:

Trends in seasonal influenza outbreaks revealed peaks that occurred earlier over time (p<0.0001) and increased in size over time (p=0.0012). The median peak week did not vary significantly by region (p=0.8541). Also, peak week and peak size were negatively correlated showing that earlier epidemics result in higher ILI rates. The timing of the epidemic differed depending on the dominant subtype circulating (p=0.0337) with subtype 2009 H1N1peaks occurring 3.5 weeks earlier than H1 peaks; however, subtype did not have a significant effect on the size of the epidemic peak (p=0.1984).

Conclusion:

A significant decrease in peak week and a significant increase in peak size were observed over time, revealing a trend of earlier and more intense seasonal flu peaks. Since earlier epidemics are correlated with higher rates of ILI, anticipating earlier seasonal peaks highlights the importance of vaccination and other flu prevention strategies being utilized early in the flu season.

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