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Montgomery MP, Morris SE, Rolfes MA, Kittikraisak W, Samuels AM, Biggerstaff M, Davis WW, Reed C, Olsen SJ. The role of asymptomatic infections in influenza transmission: what do we really know. THE LANCET. INFECTIOUS DISEASES 2024; 24:e394-e404. [PMID: 38128563 PMCID: PMC11127787 DOI: 10.1016/s1473-3099(23)00619-9] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 07/31/2023] [Revised: 09/02/2023] [Accepted: 09/18/2023] [Indexed: 12/23/2023]
Abstract
Before the COVID-19 pandemic, the role of asymptomatic influenza virus infections in influenza transmission was uncertain. However, the importance of asymptomatic infection with SARS-CoV-2 for onward transmission of COVID-19 has led experts to question whether the role of asymptomatic influenza virus infections in transmission had been underappreciated. We discuss the existing evidence on the frequency of asymptomatic influenza virus infections, the extent to which they contribute to infection transmission, and remaining knowledge gaps. We propose priority areas for further evaluation, study designs, and case definitions to address existing knowledge gaps.
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Affiliation(s)
- Martha P Montgomery
- Influenza Division, National Center for Immunization and Respiratory Diseases, US Centers for Disease Control and Prevention, Atlanta, GA, USA; Thailand Ministry of Public Health-US Centers for Disease Control and Prevention Collaboration, Department of Disease Control, Ministry of Public Health, Nonthaburi, Thailand.
| | - Sinead E Morris
- Influenza Division, National Center for Immunization and Respiratory Diseases, US Centers for Disease Control and Prevention, Atlanta, GA, USA
| | - Melissa A Rolfes
- Influenza Division, National Center for Immunization and Respiratory Diseases, US Centers for Disease Control and Prevention, Atlanta, GA, USA
| | - Wanitchaya Kittikraisak
- Influenza Division, National Center for Immunization and Respiratory Diseases, US Centers for Disease Control and Prevention, Atlanta, GA, USA; Thailand Ministry of Public Health-US Centers for Disease Control and Prevention Collaboration, Department of Disease Control, Ministry of Public Health, Nonthaburi, Thailand
| | - Aaron M Samuels
- Influenza Division, National Center for Immunization and Respiratory Diseases, US Centers for Disease Control and Prevention, Atlanta, GA, USA
| | - Matthew Biggerstaff
- Influenza Division, National Center for Immunization and Respiratory Diseases, US Centers for Disease Control and Prevention, Atlanta, GA, USA
| | - William W Davis
- Influenza Division, National Center for Immunization and Respiratory Diseases, US Centers for Disease Control and Prevention, Atlanta, GA, USA; Thailand Ministry of Public Health-US Centers for Disease Control and Prevention Collaboration, Department of Disease Control, Ministry of Public Health, Nonthaburi, Thailand
| | - Carrie Reed
- Influenza Division, National Center for Immunization and Respiratory Diseases, US Centers for Disease Control and Prevention, Atlanta, GA, USA
| | - Sonja J Olsen
- Influenza Division, National Center for Immunization and Respiratory Diseases, US Centers for Disease Control and Prevention, Atlanta, GA, USA
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Pasharawipas T. Perspectives Concerning Various Symptoms of SARS-CoV-2 Detected Individuals. Open Microbiol J 2021. [DOI: 10.2174/1874285802115010152] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022] Open
Abstract
After exposure to SARS-CoV-2, varying symptoms of COVID-19 ranging from asymptomatic symptoms to morbidity and mortality have been exhibited in each individual. SARS-CoV-2 requires various cellular molecules for penetration into a target host cell. Angiotensin-converting enzyme2 (ACE2) acts as the viral receptor molecule. After attachment, SARS-CoV-2 also requires the transmembrane protease serine-2 (TMPRSS-2) and furin molecules, which serve as co-receptors for penetration into the target cell and for subsequent replication. In the meantime, a major histocompatibility complex (MHC) is required for the induction of adaptive immune cells, especially cytotoxic T cells and helper T cells, to clear the virally infected cells. This perspective review article proposes different aspects to explain the varying symptoms of the individuals who have been exposed to SARS-CoV-2, which relates to the polymorphisms of these involved molecules.
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Silent Infection of B and CD8 + T Lymphocytes by Influenza A Virus in Children with Tonsillar Hypertrophy. J Virol 2020; 94:JVI.01969-19. [PMID: 32075928 DOI: 10.1128/jvi.01969-19] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/22/2019] [Accepted: 02/12/2020] [Indexed: 12/11/2022] Open
Abstract
Influenza A viruses (IAVs) cause more than 2 million annual episodes of seasonal acute respiratory infections (ARI) and approximately 500,000 deaths worldwide. Depending on virus strain and host immune status, acute infections by IAV may reach sites other than the respiratory tract. In the present study, IAV RNA and antigens were searched for in tissues of palatine tonsils and adenoids removed from patients without ARI symptoms. A real-time reverse transcriptase PCR (RT-PCR) screening revealed that 8 tissue samples from 7 patients out of 103 were positive for IAV. Positive samples were subjected to next-generation sequencing (NGS) and 3 of 8 tissues yielded complete IAV pH1N1 genomes, whereas in 5 samples, the PB1 gene was not fully assembled. Phylogenetic analysis placed tonsil-derived IAV in clusters clearly segregated from contemporaneous Brazilian viruses. Flow cytometry of dispersed tissue fragments and serial immunohistochemistry of paraffin-embedded sections of naturally infected biopsies indicated that CD20+ B lymphocytes, CD8+ T lymphocytes, and CD11c+ cells are susceptible to IAV infection. We sought to investigate whether these lymphoid tissues could be sites of viral replication and sources of viable virus particles. MDCK cells were inoculated with tissue lysates, enabling recovery of one IAV isolate confirmed by immunofluorescence, reverse transcriptase quantitative PCR (RT-qPCR), and NGS. The data indicate that lymphoid tissues not only harbor expression of IAV proteins but also contain infectious virus. Asymptomatic long-term infection raises the possibility of IAV shedding from tonsils, which may have an impact on host-to-host transmission.IMPORTANCE Influenza A virus (IAV) infections are important threats to human health worldwide. Although extensively studied, some aspects of virus pathogenesis and tissue tropism remain unclear. Here, by different strategies, we describe the asymptomatic infection of human lymphoid organs by IAV in children. Our results indicate that IAV was not only detected and isolated from human tonsils but displayed unique genetic features in comparison with those of contemporaneous IAVs circulating in Brazil and detected in swabs and nasal washes. Inside the tissue microenvironment, immune cells were shown to be carrying IAV antigens, especially B and T CD8+ lymphocytes. Taken together, these results suggest that human lymphoid tissues can be sites of silent IAV infections with possible impact on virus shedding to the population.
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Clinique et diagnostic de la grippe saisonnière. ACTUALITES PHARMACEUTIQUES 2019. [DOI: 10.1016/j.actpha.2019.07.005] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022]
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Jenkin DC, Mahgoub H, Morales KF, Lambach P, Nguyen-Van-Tam JS. A rapid evidence appraisal of influenza vaccination in health workers: An important policy in an area of imperfect evidence. Vaccine X 2019; 2:100036. [PMID: 31384750 PMCID: PMC6668237 DOI: 10.1016/j.jvacx.2019.100036] [Citation(s) in RCA: 24] [Impact Index Per Article: 4.8] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/01/2019] [Revised: 07/04/2019] [Accepted: 07/05/2019] [Indexed: 11/21/2022] Open
Abstract
INTRODUCTION The World Health Organization recommends vaccination of health workers (HWs) against influenza, but low uptake is intransigent.We conducted a Rapid Evidence Appraisal on: the risk of influenza in HWs, transmission risk from HWs to patients, the benefit of HW vaccination, and strategies for improving uptake. We aimed to capture a 'whole-of-system' perspective to consider possible benefits for HWs, employers and patients. METHODS We executed a comprehensive search of the available literature published from 2006 to 2018 in the English language. We developed search terms for seven separate questions following the PICO framework (population, intervention, comparators, outcomes) and queried nine databases. RESULTS Of 3784 publications identified, 52 met inclusion criteria. Seven addressed HW influenza risk, of which four found increased risk; 15 addressed influenza vaccine benefit to HWs or their employers, of which 10 found benefit; 11 addressed influenza transmission from HWs to patients, of which 6 found evidence for transmission; 12 unique studies addressed whether vaccinating HWs produced patient benefit, of which 9 concluded benefits accrued. Regarding the number of HWs needed to vaccinate (NNV) to deliver patient benefit, NNV estimates ranged from 3 to 36,000 but were in significant disagreement. Fourteen studies provided insights on strategies to improve uptake; the strongest evidence was for mandatory vaccination. CONCLUSIONS The evidence on most questions related to influenza vaccination in HWs is mixed and often of low-quality. Substantial heterogeneity exists in terms of study designs and settings, making comparison between studies difficult. Notwithstanding these limitations, a majority of studies suggests that influenza vaccination benefit HWs and their employers; and HWs are implicated in transmission events. The effects of vaccinating HWs on patient morbidity and mortality may include reductions in all-cause mortality and influenza-like illness (ILI). Taken together, the evidence suggests that HW vaccination is an important policy for HWs themselves, their employers, and their patients.
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Key Words
- GAVI, the global alliance for vaccines and immunization
- HW, health workers
- Health worker
- Healthcare
- ILI, influenza like illness
- Influenza
- LTCF, long-term care facility(ies)
- NNV, number needed to vaccinate
- OR, odds ratio
- Policy
- RCTs, randomised controlled trials
- RR, relative risk
- Transmission
- Vaccine
- WHO, World Health organization
- cRCTs, clustered randomised controlled trials
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Affiliation(s)
- Dawn C. Jenkin
- Health Protection and Influenza Research Group (WHO Collaborating Centre), University of Nottingham School of Medicine, United Kingdom
| | - Hamid Mahgoub
- East of England Health Protection Team, Public Health England, United Kingdom
| | | | | | - Jonathan S. Nguyen-Van-Tam
- Health Protection and Influenza Research Group (WHO Collaborating Centre), University of Nottingham School of Medicine, United Kingdom
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Baier C, Linderkamp C, Beilken A, Thol F, Heuser M, Ebadi E, Ganzenmueller T, Heim A, Bange FC. Influenza and respiratory syncytial virus screening for the detection of asymptomatically infected patients in hematology and oncology. GMS HYGIENE AND INFECTION CONTROL 2018; 13:Doc08. [PMID: 30460173 PMCID: PMC6234716 DOI: 10.3205/dgkh000314] [Citation(s) in RCA: 7] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [Key Words] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Indexed: 12/23/2022]
Abstract
Introduction: Respiratory syncytial virus (RSV) and influenza virus infections are a significant healthcare risk for immunocompromised patients. In addition to community onset, nosocomial acquisition and transmission may also occur. Detection of asymptomatic shedders (e.g., patients in the incubation period or immunosuppressed long term shedders) facilitates control of nosocomial transmission. Methods: To strengthen the existing infection control concept, a PCR-based screening for RSV and influenza virus was implemented for all patients lacking respiratory symptoms (asymptomatic patients) who were hospitalized on an adult and a pediatric hemato-oncological ward. Laboratory results of this screening were analyzed retrospectively. Results: 665 respiratory specimens were obtained for screening from 251 patients (26% were 18 years and younger) from December 2016 to April 2017. In 23 patients without respiratory symptoms, either influenza virus or RSV infection was found, resulting in a detection rate of about 9%. In 6 patients, the infection was presumably detected during the incubation period, because an increase of viral load was observed in subsequent specimens. Positive screening results facilitated timely implementation of adequate infection control precautions. Nosocomial clusters of RSV or influenza were not detected during the screening period on the two wards. Conclusion: The seasonal screening program expanded our existing infection control concept in terms of patients lacking respiratory symptoms who shed influenza virus or RSV. It enabled us to identify 23 RSV or influenza infections in patients lacking respiratory symptoms in a 4-month period and thus to rapidly take isolation precautions.
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Affiliation(s)
- Claas Baier
- Institute for Medical Microbiology and Hospital Epidemiology, Hannover Medical School (MHH), Hannover, Germany
| | - Christin Linderkamp
- Department of Pediatric Hematology and Oncology, Hannover Medical School (MHH), Hannover, Germany
| | - Andreas Beilken
- Department of Pediatric Hematology and Oncology, Hannover Medical School (MHH), Hannover, Germany
| | - Felicitas Thol
- Department of Hematology, Hemostasis, Oncology and Stem Cell Transplantation, Hannover Medical School (MHH), Hannover, Germany
| | - Michael Heuser
- Department of Hematology, Hemostasis, Oncology and Stem Cell Transplantation, Hannover Medical School (MHH), Hannover, Germany
| | - Ella Ebadi
- Institute for Medical Microbiology and Hospital Epidemiology, Hannover Medical School (MHH), Hannover, Germany
| | | | - Albert Heim
- Institute of Virology, Hannover Medical School (MHH), Hannover, Germany
| | - Franz-Christoph Bange
- Institute for Medical Microbiology and Hospital Epidemiology, Hannover Medical School (MHH), Hannover, Germany
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Chen HF, Zhang LL, Fang YB, Chen M, Guo C, Yi HL, Tao MT, Li Y, Dai CF. [A preliminary study on the disappearance time of influenza virus antigen]. ZHONGGUO DANG DAI ER KE ZA ZHI = CHINESE JOURNAL OF CONTEMPORARY PEDIATRICS 2017; 19:564-566. [PMID: 28506350 PMCID: PMC7389127 DOI: 10.7499/j.issn.1008-8830.2017.05.017] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Subscribe] [Scholar Register] [Received: 12/04/2016] [Accepted: 02/05/2017] [Indexed: 06/07/2023]
Abstract
OBJECTIVE To investigate the antigen clearance time, time to symptom disappearance, and the association between them using immunofluorescence assay for dynamic monitoring of influenza virus antigen in children with influenza. METHODS A total of 1 063 children suspected of influenza who visited the Hunan People's Hospital from March to April, 2016 were enrolled. The influenza A/B virus antigen detection kit (immunofluorescence assay) was used for influenza virus antigen detection. The children with positive results were given oseltamivir as the antiviral therapy and were asked to re-examine influenza virus antigen at 5, 5-7, and 7 days after onset. RESULTS Of all children suspected of influenza, 560 (52.68%) had an influenza virus infection. A total of 215 children with influenza virus infection were followed up. The clearance rate of influenza virus antigen was 9.8% (21 cases) within 5 days after onset. The cumulative clearance rate of influenza virus antigen was 32.1% (69 cases) within 5-7 days, and 98.1% (211 cases) within 7-10 days after onset. Among these children, 6 children (2.8%) achieved the improvement in clinical symptoms within 3 days after onset. The cumulative rate of symptom improvement was 84.7% (182 cases) within 3-5 days after onset, and 100% achieved the improvement after 5 days of onset. CONCLUSIONS The time to improvement in symptoms after treatment is earlier than antigen clearance time. Almost all of the children achieve influenza virus antigen clearance 7-10 days after onset. Therefore, it is relatively safe for children to go back to school within 7-10 days after onset when symptoms disappear.
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Affiliation(s)
- Hao-Feng Chen
- Pediatric Medical Center, Hunan People's Hospital, Changsha 410005, China.
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Vidaña B, Martínez J, Martorell J, Montoya M, Córdoba L, Pérez M, Majó N. Involvement of the different lung compartments in the pathogenesis of pH1N1 influenza virus infection in ferrets. Vet Res 2016; 47:113. [PMID: 27825367 PMCID: PMC5101722 DOI: 10.1186/s13567-016-0395-0] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/19/2016] [Accepted: 10/10/2016] [Indexed: 12/29/2022] Open
Abstract
Severe cases after pH1N1 infection are consequence of interstitial pneumonia triggered by alveolar viral replication and an exacerbated host immune response, characterized by the up-regulation of pro-inflammatory cytokines and the influx of inflammatory leukocytes to the lungs. Different lung cell populations have been suggested as culprits in the unregulated innate immune responses observed in these cases. This study aims to clarify this question by studying the different induction of innate immune molecules by the distinct lung anatomic compartments (vascular, alveolar and bronchiolar) of ferrets intratracheally infected with a human pH1N1 viral isolate, by means of laser microdissection techniques. The obtained results were then analysed in relation to viral quantification in the different anatomic areas and the histopathological lesions observed. More severe lung lesions were observed at 24 h post infection (hpi) correlating with viral antigen detection in bronchiolar and alveolar epithelial cells. However, high levels of viral RNA were detected in all anatomic compartments throughout infection. Bronchiolar areas were the first source of IFN-α and most pro-inflammatory cytokines, through the activation of RIG-I. In contrast, vascular areas contributed with the highest induction of CCL2 and other pro-inflammatory cytokines, through the activation of TLR3.
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Affiliation(s)
- Beatriz Vidaña
- Departament de Sanitat i Anatomia Animals, Universitat Autònoma de Barcelona, Bellaterra, Barcelona, Spain.,IRTA, Centre de Recerca en Sanitat Animal (CReSA, IRTA-UAB), Campus de la Universitat Autònoma de Barcelona, Bellaterra, Barcelona, Spain
| | - Jorge Martínez
- Departament de Sanitat i Anatomia Animals, Universitat Autònoma de Barcelona, Bellaterra, Barcelona, Spain. .,UAB, Centre de Recerca en Sanitat Animal (CReSA, IRTA-UAB), Campus de la Universitat Autònoma de Barcelona, Bellaterra, Barcelona, Spain.
| | - Jaime Martorell
- Departament de Medicina i Cirurgia Animals, Universitat Autònoma de Barcelona, Bellaterra, Barcelona, Spain
| | - María Montoya
- IRTA, Centre de Recerca en Sanitat Animal (CReSA, IRTA-UAB), Campus de la Universitat Autònoma de Barcelona, Bellaterra, Barcelona, Spain
| | - Lorena Córdoba
- IRTA, Centre de Recerca en Sanitat Animal (CReSA, IRTA-UAB), Campus de la Universitat Autònoma de Barcelona, Bellaterra, Barcelona, Spain
| | - Mónica Pérez
- IRTA, Centre de Recerca en Sanitat Animal (CReSA, IRTA-UAB), Campus de la Universitat Autònoma de Barcelona, Bellaterra, Barcelona, Spain
| | - Natàlia Majó
- Departament de Sanitat i Anatomia Animals, Universitat Autònoma de Barcelona, Bellaterra, Barcelona, Spain.,UAB, Centre de Recerca en Sanitat Animal (CReSA, IRTA-UAB), Campus de la Universitat Autònoma de Barcelona, Bellaterra, Barcelona, Spain
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