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Morris SE, Nguyen HQ, Grijalva CG, Hanson KE, Zhu Y, Biddle JE, Meece JK, Halasa NB, Chappell JD, Mellis AM, Reed C, Biggerstaff M, Belongia EA, Talbot HK, Rolfes MA. Influenza virus shedding and symptoms: Dynamics and implications from a multiseason household transmission study. PNAS NEXUS 2024; 3:pgae338. [PMID: 39246667 PMCID: PMC11378077 DOI: 10.1093/pnasnexus/pgae338] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 03/06/2024] [Accepted: 07/07/2024] [Indexed: 09/10/2024]
Abstract
Isolation of symptomatic infectious persons can reduce influenza transmission. However, virus shedding that occurs without symptoms will be unaffected by such measures. Identifying effective isolation strategies for influenza requires understanding the interplay between individual virus shedding and symptom presentation. From 2017 to 2020, we conducted a case-ascertained household transmission study using influenza real-time RT-qPCR testing of nasal swabs and daily symptom diary reporting for up to 7 days after enrolment (≤14 days after index onset). We assumed real-time RT-qPCR cycle threshold (Ct) values were indicators of quantitative virus shedding and used symptom diaries to create a score that tracked influenza-like illness (ILI) symptoms (fever, cough, or sore throat). We fit phenomenological nonlinear mixed-effects models stratified by age and vaccination status and estimated two quantities influencing isolation effectiveness: shedding before symptom onset and shedding that might occur once isolation ends. We considered different isolation end points (including 24 h after fever resolution or 5 days after symptom onset) and assumptions about the infectiousness of Ct shedding trajectories. Of the 116 household contacts with ≥2 positive tests for longitudinal analyses, 105 (91%) experienced ≥1 ILI symptom. On average, children <5 years experienced greater peak shedding, longer durations of shedding, and elevated ILI symptom scores compared with other age groups. Most individuals (63/105) shed <10% of their total shed virus before symptom onset, and shedding after isolation varied substantially across individuals, isolation end points, and infectiousness assumptions. Our results can inform strategies to reduce transmission from symptomatic individuals infected with influenza.
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Affiliation(s)
- Sinead E Morris
- Influenza Division, Centers for Disease Control and Prevention, Atlanta, GA 30329, USA
- Goldbelt Professional Services, Chesapeake, VA 23320, USA
| | - Huong Q Nguyen
- Marshfield Clinic Research Institute, Marshfield, WI 54449, USA
| | | | - Kayla E Hanson
- Marshfield Clinic Research Institute, Marshfield, WI 54449, USA
| | - Yuwei Zhu
- Vanderbilt University Medical Center, Nashville, TN 37232, USA
| | - Jessica E Biddle
- Influenza Division, Centers for Disease Control and Prevention, Atlanta, GA 30329, USA
| | | | | | | | - Alexandra M Mellis
- Influenza Division, Centers for Disease Control and Prevention, Atlanta, GA 30329, USA
| | - Carrie Reed
- Influenza Division, Centers for Disease Control and Prevention, Atlanta, GA 30329, USA
| | - Matthew Biggerstaff
- Influenza Division, Centers for Disease Control and Prevention, Atlanta, GA 30329, USA
| | | | - H Keipp Talbot
- Vanderbilt University Medical Center, Nashville, TN 37232, USA
| | - Melissa A Rolfes
- Influenza Division, Centers for Disease Control and Prevention, Atlanta, GA 30329, USA
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Chung JR, Kim SS, Flannery B, Smith ME, Dunnigan K, Raiyani C, Murthy K, Gaglani M, Jackson ML, Jackson LA, Bear T, Moehling Geffel K, Nowalk MP, Zimmerman RK, Martin ET, Lamerato L, McLean HQ, King JP, Belongia EA, Thompson MG, Patel M. Vaccine-associated attenuation of subjective severity among outpatients with influenza. Vaccine 2022; 40:4322-4327. [PMID: 35710506 PMCID: PMC9638984 DOI: 10.1016/j.vaccine.2022.06.019] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/05/2022] [Revised: 05/24/2022] [Accepted: 06/05/2022] [Indexed: 11/18/2022]
Abstract
Influenza vaccines can mitigate illness severity, including reduced risk of ICU admission and death, in people with breakthrough infection. Less is known about vaccine attenuation of mild/moderate influenza illness. We compared subjective severity scores in vaccinated and unvaccinated persons with medically attended illness and laboratory-confirmed influenza. Participants were prospectively recruited when presenting for care at five US sites over nine seasons. Participants aged ≥ 16 years completed the EQ-5D-5L visual analog scale (VAS) at enrollment. After controlling for potential confounders in a multivariable model, including age and general health status, VAS scores were significantly higher among 2,830 vaccinated participants compared with 3,459 unvaccinated participants, indicating vaccinated participants felt better at the time of presentation for care. No differences in VAS scores were observed by the type of vaccine received among persons aged ≥ 65 years. Our findings suggest vaccine-associated attenuation of milder influenza illness is possible.
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Affiliation(s)
- Jessie R Chung
- U.S. Centers for Disease Control and Prevention, Influenza Division, Atlanta, GA, United States.
| | - Sara S Kim
- U.S. Centers for Disease Control and Prevention, Influenza Division, Atlanta, GA, United States
| | - Brendan Flannery
- U.S. Centers for Disease Control and Prevention, Influenza Division, Atlanta, GA, United States
| | | | | | | | | | - Manjusha Gaglani
- Baylor Scott & White Health, Temple, TX, United States; Texas A&M University College of Medicine, Temple, TX, United States
| | - Michael L Jackson
- Kaiser Permanente Washington Health Research Institute, Seattle, WA, United States
| | - Lisa A Jackson
- Kaiser Permanente Washington Health Research Institute, Seattle, WA, United States
| | - Todd Bear
- University of Pittsburgh, United States
| | | | | | | | - Emily T Martin
- University of Michigan School of Public Health, Ann Arbor, MI, United States
| | - Lois Lamerato
- Henry Ford Health System, Detroit, MI, United States
| | - Huong Q McLean
- Marshfield Clinic Research Institute, Marshfield, WI, United States
| | - Jennifer P King
- Marshfield Clinic Research Institute, Marshfield, WI, United States
| | | | - Mark G Thompson
- U.S. Centers for Disease Control and Prevention, Influenza Division, Atlanta, GA, United States
| | - Manish Patel
- U.S. Centers for Disease Control and Prevention, Influenza Division, Atlanta, GA, United States
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