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Risk Factors for Infection with Influenza A(H3N2) virus on a US University Campus, October–November 2021
  • +7
  • Nathaniel Lewis,
  • Miranda Delahoy,
  • Kelsey Sumner,
  • Adam Lauring,
  • Emily Bendall,
  • Lindsey Mortenson,
  • Aleksandra Stamper,
  • Elizabeth Edwards,
  • Brendan Flannery,
  • Emily Martin
Nathaniel Lewis
Centers for Disease Control and Prevention

Corresponding Author:pha6@cdc.gov

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Miranda Delahoy
Centers for Disease Control and Prevention
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Kelsey Sumner
Centers for Disease Control and Prevention
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Adam Lauring
University of Michigan Medical School
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Emily Bendall
University of Michigan Medical School
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Lindsey Mortenson
University of Michigan Medical School
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Aleksandra Stamper
University of Michigan Medical School
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Elizabeth Edwards
University of Michigan Medical School
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Brendan Flannery
Centers for Disease Control and Prevention
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Emily Martin
University of Michigan
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Abstract

Background: Knowledge of the specific dynamics of influenza introduction and spread in university settings is limited. Methods: Persons with acute respiratory illness symptoms received influenza testing by molecular assay during October 6–November 23, 2022. Viral sequencing and phylogenetic analysis were conducted on nasal swab samples from case-patients. Case-control analysis of a voluntary survey of persons tested was used to identify factors associated with influenza; logistic regression was conducted to calculate odds ratios and 95% CIs. A subset of case-patients tested during the first month of the outbreak was interviewed to identify sources of introduction and early spread. Results: Among 3,268 persons tested, 788 (24.1%) tested positive for influenza; 744 (22.8%) were included in the survey analysis. All 380 sequenced specimens were influenza A (H3N2) virus clade 3C.2a1b.2a.2, suggesting rapid transmission. Influenza (OR [95% CI]) was associated with indoor congregate dining (1.43 [1.002–2.03]), attending large gatherings indoors (1.83 [1.26–2.66]) or outdoors (2.33 [1.64–3.31]), and varied by residence type (apartment with ≥1 roommate: 2.93 [1.21–7.11], residence hall room alone: 4.18 [1.31–13.31], or with roommate: 6.09 [2.46–15.06], or fraternity/sorority house: 15.13 [4.30–53.21], all compared with single-dwelling apartment). Odds of influenza were lower among persons who left campus for ≥1 day during the week before their influenza test (0.49 [0.32–0.75]). Almost all early cases reported attending large events. Conclusions: Congregate living and activity settings on university campuses can lead to rapid spread of influenza following introduction. Isolating following a positive influenza test or administering antiviral medications to exposed persons may help mitigate outbreaks.
07 Mar 2023Submitted to Influenza and other respiratory viruses
08 Mar 2023Submission Checks Completed
08 Mar 2023Assigned to Editor
10 Mar 2023Reviewer(s) Assigned
12 Apr 2023Review(s) Completed, Editorial Evaluation Pending
12 Apr 2023Editorial Decision: Revise Minor
04 May 20231st Revision Received
08 May 2023Submission Checks Completed
08 May 2023Assigned to Editor
08 May 2023Editorial Decision: Accept