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Zhao X, Gu Y, Tang X, Jiang C, Fang F, Chu W, Tao L, Zhang X, Chen M, Wu H, Xie Y, Liu J, Teng Z. Whole-genome analysis of circulating influenza A virus (H3N2) strains in Shanghai, China from 2005 to 2023. Emerg Microbes Infect 2024:2396867. [PMID: 39193626 DOI: 10.1080/22221751.2024.2396867] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 08/29/2024]
Abstract
Seasonal influenza A virus subtype H3N2 (A/H3N2) circulates globally and has been linked to higher hospitalization rates and summer outbreaks in temperate regions. Here, A/H3N2 circulation in Shanghai, China was systematically studied using data and materials generated by the Shanghai influenza surveillance network from 2005 to 2023. Time-series analysis of incidence and subtyping data showed that A/H3N2 co-circulated with other (sub)types and dominated in multiple seasonal influenza peaks, preferentially in summer. Whole genomes of 528 representative strains were sequenced, and spatiotemporal phylodynamic analysis using these and GISAID-archived sequences demonstrated that in the years before the COVID-19 pandemic, phylogenetically similar strains were circulating locally and elsewhere. However, clade 1a.1 (within 3C.2a.1b.2a), circulated in and only in Shanghai and domestically in 2022, while the sibling clade 2 predominated in other regions. Interestingly, clade 1a.1 was swiftly and completely replaced by clade 2, mostly 2a.3a.1, at the start of 2023. In hemagglutination inhibition and neutralization assays, sera from healthy donors collected in 2022 displayed higher or similar reactivity against 2a.3a.1 compared to 1a.1. By contrast, transcription and replication competence of 2a.3a.1 in MDCK cells was higher than 1a.1. These results indicated that instead of antigenicity differences enabling evasion of pre-existing immunity, higher replicative capability more likely contributed to 2a.3a.1 viruses achieving dominance in China. In addition to summarizing patterns of A/H3N2 local circulation in Shanghai, this work revealed an unusual episode in A/H3N2 global circulation and evolution dynamics in connection to the COVID-19 pandemic and explored possible mechanistic explanations.
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Affiliation(s)
- Xue Zhao
- Virus Testing Laboratory, Pathogen Testing Center, Shanghai Municipal Center for Disease Control and Prevention, Shanghai, People's Republic of China
| | - Yijing Gu
- Virus Testing Laboratory, Pathogen Testing Center, Shanghai Municipal Center for Disease Control and Prevention, Shanghai, People's Republic of China
| | - Xiaode Tang
- Microbiological Testing Department, Shanghai Baoshan District Center for Disease Prevention and Control, Shanghai, People's Republic of China
| | - Chenyan Jiang
- Virus Testing Laboratory, Pathogen Testing Center, Shanghai Municipal Center for Disease Control and Prevention, Shanghai, People's Republic of China
| | - Fanghao Fang
- Virus Testing Laboratory, Pathogen Testing Center, Shanghai Municipal Center for Disease Control and Prevention, Shanghai, People's Republic of China
| | - Wei Chu
- Microbiological Laboratory, Shanghai Huangpu District Center for Disease Prevention and Control, Shanghai, People's Republic of China
| | - Lixin Tao
- Microbiological Laboratory, Shanghai Fengxian District Center for Disease Prevention and Control, Shanghai, People's Republic of China
| | - Xi Zhang
- Virus Testing Laboratory, Pathogen Testing Center, Shanghai Municipal Center for Disease Control and Prevention, Shanghai, People's Republic of China
| | - Min Chen
- Virus Testing Laboratory, Pathogen Testing Center, Shanghai Municipal Center for Disease Control and Prevention, Shanghai, People's Republic of China
| | - Huanyu Wu
- Virus Testing Laboratory, Pathogen Testing Center, Shanghai Municipal Center for Disease Control and Prevention, Shanghai, People's Republic of China
| | - Youhua Xie
- Key Laboratory of Medical Molecular Virology (MOE/MOH/CAMS) and Shanghai Key Laboratory of Medical Epigenetics, Department of Microbiology and Parasitology and Institutes of Biomedical Sciences, School of Basic Medical Sciences and Shanghai Institute of Infectious Diseases and Biosecurity, Shanghai Medical College, Fudan University, Shanghai, People's Republic of China
| | - Jing Liu
- Key Laboratory of Medical Molecular Virology (MOE/MOH/CAMS) and Shanghai Key Laboratory of Medical Epigenetics, Department of Microbiology and Parasitology and Institutes of Biomedical Sciences, School of Basic Medical Sciences and Shanghai Institute of Infectious Diseases and Biosecurity, Shanghai Medical College, Fudan University, Shanghai, People's Republic of China
| | - Zheng Teng
- Virus Testing Laboratory, Pathogen Testing Center, Shanghai Municipal Center for Disease Control and Prevention, Shanghai, People's Republic of China
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Palanki R, Yamagata H, Mitchell MJ. OLAH connects fatty acid metabolism to the severity of respiratory viral disease. Cell 2024; 187:4549-4551. [PMID: 39178832 DOI: 10.1016/j.cell.2024.07.032] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/01/2024] [Revised: 07/18/2024] [Accepted: 07/19/2024] [Indexed: 08/26/2024]
Abstract
Respiratory virus infections may cause profound respiratory illness, yet the factors that underlie disease severity are not well understood. In this issue of Cell, Jia, Crawford, et al.1 identify the role of oleoyl-ACP-hydrolase (OLAH) in mediating life-threatening inflammation associated with viral respiratory disease severity.
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Affiliation(s)
- Rohan Palanki
- Department of Bioengineering, University of Pennsylvania, Philadelphia, PA 19104, USA; Perelman School of Medicine, University of Pennsylvania, Philadelphia, PA 19104, USA
| | - Hannah Yamagata
- Department of Bioengineering, University of Pennsylvania, Philadelphia, PA 19104, USA
| | - Michael J Mitchell
- Department of Bioengineering, University of Pennsylvania, Philadelphia, PA 19104, USA; Center for Precision Engineering for Health, University of Pennsylvania, Philadelphia, PA 19104, USA; Institute for RNA Innovation, University of Pennsylvania, Philadelphia, PA 19104, USA; Abramson Cancer Center, Perelman School of Medicine, University of Pennsylvania, Philadelphia, PA 19104, USA; Center for Cellular Immunotherapies, Perelman School of Medicine, University of Pennsylvania, Philadelphia, PA 19104, USA; Institute for Immunology, Perelman School of Medicine, University of Pennsylvania, Philadelphia, PA 19104, USA; Cardiovascular Institute, Perelman School of Medicine, University of Pennsylvania, Philadelphia, PA 19104, USA; Institute for Regenerative Medicine, Perelman School of Medicine, University of Pennsylvania, Philadelphia, PA 19104, USA.
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3
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Zhu W, Gu L. Resurgence of seasonal influenza driven by A/H3N2 and B/Victoria in succession during the 2023-2024 season in Beijing showing increased population susceptibility. J Med Virol 2024; 96:e29751. [PMID: 38884384 DOI: 10.1002/jmv.29751] [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: 03/31/2024] [Revised: 05/19/2024] [Accepted: 06/10/2024] [Indexed: 06/18/2024]
Abstract
During the COVID-19 pandemic, non-pharmaceutical interventions were introduced to reduce exposure to respiratory viruses. However, these measures may have led to an "immunity debt" that could make the population more vulnerable. The goal of this study was to examine the transmission dynamics of seasonal influenza in the years 2023-2024. Respiratory samples from patients with influenza-like illness were collected and tested for influenza A and B viruses. The electronic medical records of index cases from October 2023 to March 2024 were analyzed to determine their clinical and epidemiological characteristics. A total of 48984 positive cases were detected, with a pooled prevalence of 46.9% (95% CI 46.3-47.5). This season saw bimodal peaks of influenza activity, with influenza A peaked in week 48, 2023, and influenza B peaked in week 1, 2024. The pooled positive rates were 28.6% (95% CI 55.4-59.6) and 18.3% (95% CI 18.0-18.7) for influenza A and B viruses, respectively. The median values of instantaneous reproduction number were 5.5 (IQR 3.0-6.7) and 4.6 (IQR 2.4-5.5), respectively. The hospitalization rate for influenza A virus (2.2%, 95% CI 2.0-2.5) was significantly higher than that of influenza B virus (1.1%, 95% CI 0.9-1.4). Among the 17 clinical symptoms studied, odds ratios of 15 symptoms were below 1 when comparing influenza A and B positive inpatients, with headache, weakness, and myalgia showing significant differences. This study provides an overview of influenza dynamics and clinical symptoms, highlighting the importance for individuals to receive an annual influenza vaccine.
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Affiliation(s)
- Wentao Zhu
- Department of Infectious Diseases and Clinical Microbiology, Beijing Institute of Respiratory Medicine and Beijing Chao-Yang Hospital, Capital Medical University, Beijing, P.R. China
| | - Li Gu
- Department of Infectious Diseases and Clinical Microbiology, Beijing Institute of Respiratory Medicine and Beijing Chao-Yang Hospital, Capital Medical University, Beijing, P.R. China
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Morris S, Gilmer M, Threlkel R, Brammer L, Budd A, Iuliano A, Reed C, Biggerstaff M. Detection of Novel Influenza Viruses Through Community and Healthcare Testing: Implications for Surveillance Efforts in the United States. Influenza Other Respir Viruses 2024; 18:e13315. [PMID: 38798083 PMCID: PMC11128772 DOI: 10.1111/irv.13315] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/03/2023] [Revised: 04/27/2024] [Accepted: 04/29/2024] [Indexed: 05/29/2024] Open
Abstract
BACKGROUND Novel influenza viruses pose a potential pandemic risk, and rapid detection of infections in humans is critical to characterizing the virus and facilitating the implementation of public health response measures. METHODS We use a probabilistic framework to estimate the likelihood that novel influenza virus cases would be detected through testing in different community and healthcare settings (urgent care, emergency department, hospital, and intensive care unit [ICU]) while at low frequencies in the United States. Parameters were informed by data on seasonal influenza virus activity and existing testing practices. RESULTS In a baseline scenario reflecting the presence of 100 novel virus infections with similar severity to seasonal influenza viruses, the median probability of detecting at least one infection per month was highest in urgent care settings (72%) and when community testing was conducted at random among the general population (77%). However, urgent care testing was over 15 times more efficient (estimated as the number of cases detected per 100,000 tests) due to the larger number of tests required for community testing. In scenarios that assumed increased clinical severity of novel virus infection, median detection probabilities increased across all healthcare settings, particularly in hospitals and ICUs (up to 100%) where testing also became more efficient. CONCLUSIONS Our results suggest that novel influenza virus circulation is likely to be detected through existing healthcare surveillance, with the most efficient testing setting impacted by the disease severity profile. These analyses can help inform future testing strategies to maximize the likelihood of novel influenza detection.
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Affiliation(s)
- Sinead E. Morris
- Influenza DivisionCenters for Disease Control and PreventionAtlantaGeorgiaUSA
- Goldbelt Professional ServicesChesapeakeVirginiaUSA
| | - Matthew Gilmer
- Influenza DivisionCenters for Disease Control and PreventionAtlantaGeorgiaUSA
- Goldbelt Professional ServicesChesapeakeVirginiaUSA
| | - Ryan Threlkel
- Influenza DivisionCenters for Disease Control and PreventionAtlantaGeorgiaUSA
| | - Lynnette Brammer
- Influenza DivisionCenters for Disease Control and PreventionAtlantaGeorgiaUSA
| | - Alicia P. Budd
- Influenza DivisionCenters for Disease Control and PreventionAtlantaGeorgiaUSA
| | - A. Danielle Iuliano
- Influenza DivisionCenters for Disease Control and PreventionAtlantaGeorgiaUSA
| | - Carrie Reed
- Influenza DivisionCenters for Disease Control and PreventionAtlantaGeorgiaUSA
| | - Matthew Biggerstaff
- Influenza DivisionCenters for Disease Control and PreventionAtlantaGeorgiaUSA
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Rus MA, Ghițoaica B, Lazăr AL, Man MA, Briciu VT, Muntean MI, Leucuța DC, Lupșe MS. Changes in Epidemiology and Antibiotic Prescription of Influenza: Before and after the Emergence of COVID-19. Pharmaceuticals (Basel) 2024; 17:181. [PMID: 38399395 PMCID: PMC10893202 DOI: 10.3390/ph17020181] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/31/2023] [Revised: 01/18/2024] [Accepted: 01/25/2024] [Indexed: 02/25/2024] Open
Abstract
BACKGROUND The appearance of COVID-19 had a major impact on healthcare and the epidemiology of other diseases. Following the cessation of non-pharmacologic interventions destined to limit the spread of COVID-19, influenza reemerged. The aim of this study was to compare the pre-pandemic influenza seasons with the influenza seasons after the emergence of the COVID-19 pandemic, and to identify differences in terms of clinical characteristics, risk factors, complications, outcomes, and antiviral and antibiotic treatments. METHODS We conducted a retrospective cohort study from the Teaching Hospital of Infectious Diseases database in Cluj-Napoca, Romania. We analyzed four pre-pandemic seasons and the seasons after the onset of COVID-19. We included adult patients hospitalized with confirmed influenza between October 2016 and August 2023. Variables such as age, sex, duration of hospitalization, severity, clinical manifestations, comorbidities, and Charlson comorbidity index were assessed. RESULTS A total of 941 patients were included in the analysis. The percentage of severe influenza was similar in both groups, but mortality from influenza was significantly lower after 2022. Virtually all patients were prescribed antivirals; antibiotic prescriptions decreased in the post-COVID-19 influenza seasons. CONCLUSION The present study suggests that influenza seasons after 2022 had lower mortality and attenuated clinical presentation.
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Affiliation(s)
- Mihai Aronel Rus
- Department of Infectious Diseases, “Iuliu Hatieganu” University of Medicine and Pharmacy, 400348 Cluj-Napoca, Romania; (B.G.); (M.I.M.)
| | - Bogdan Ghițoaica
- Department of Infectious Diseases, “Iuliu Hatieganu” University of Medicine and Pharmacy, 400348 Cluj-Napoca, Romania; (B.G.); (M.I.M.)
| | | | - Maria Ancuța Man
- Teaching Hospital of Infectious Diseases, 400348 Cluj-Napoca, Romania
| | - Violeta Tincuța Briciu
- Department of Infectious Diseases, “Iuliu Hatieganu” University of Medicine and Pharmacy, 400348 Cluj-Napoca, Romania; (B.G.); (M.I.M.)
- Teaching Hospital of Infectious Diseases, 400348 Cluj-Napoca, Romania
| | - Monica Iuliana Muntean
- Department of Infectious Diseases, “Iuliu Hatieganu” University of Medicine and Pharmacy, 400348 Cluj-Napoca, Romania; (B.G.); (M.I.M.)
- Teaching Hospital of Infectious Diseases, 400348 Cluj-Napoca, Romania
| | - Daniel Corneliu Leucuța
- Department of Medical Informatics and Biostatistics, Iuliu Hatieganu University of Medicine and Pharmacy, 400349 Cluj-Napoca, Romania
| | - Mihaela Sorina Lupșe
- Department of Infectious Diseases, “Iuliu Hatieganu” University of Medicine and Pharmacy, 400348 Cluj-Napoca, Romania; (B.G.); (M.I.M.)
- Teaching Hospital of Infectious Diseases, 400348 Cluj-Napoca, Romania
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Hu T, Miles AC, Pond T, Boikos C, Maleki F, Alfred T, Lopez SMC, McGrath L. Economic burden and secondary complications of influenza-related hospitalization among adults in the US: a retrospective cohort study. J Med Econ 2024; 27:324-336. [PMID: 38343288 DOI: 10.1080/13696998.2024.2314429] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 12/11/2023] [Accepted: 02/01/2024] [Indexed: 02/23/2024]
Abstract
OBJECTIVE This study aims to describe the healthcare resource utilization (HCRU) and direct medical cost of influenza-related hospitalizations to illustrate the persistent economic burden of influenza among adults in the US. METHODS A retrospective cohort study was conducted using the PINC AI Healthcare Database. Adults hospitalized with a diagnosis of influenza between August 1-May 31 from 2016-2023 were identified and stratified by age (18-49, 50-64 and ≥65 years). The index hospitalization was defined as the individual's first influenza-related hospitalization during each season. Patient demographics, comorbidities, and hospitalization characteristics were assessed during the index hospitalization. Index hospitalization length of stay (LOS), in-hospital mortality, intensive care unit (ICU) admissions, mechanical ventilation (MV) usage, and costs were evaluated overall and by MV usage, ICU admission, and secondary complication status. Pre-index influenza-related outpatient and emergency department (ED) visits (7 days prior) were also evaluated. RESULTS Primarily initiated in the ED, the median LOS for influenza-related hospitalizations was 3-4 days. Inpatient mortality increased with age (2.2-4.4%). Combined mean hospitalization and initial ED visit costs were $12,556-$14,494 (2017/18; high severity season) and $11,384-$12,896 (2022/23; most recent season). Compared to other age groups, adults ≥65 years had higher proportions of hospitalization with no MV or ICU usage. Adults 18-49 years had the highest proportion of ICU admission only, whereas adults 50-64 years had the highest MV usage only and both MV and ICU admission. MV and/or ICU usage was associated with higher hospitalization costs. Increasing proportionally with age, the majority of influenza-related hospitalizations had a secondary complication diagnosis, which were associated with elevated costs. LIMITATIONS Analysis of this hospital-based administrative database relied on coding accuracy. Only hospital system-associated outpatient/ED visits were captured; the full scope of HCRU was under-ascertained. CONCLUSIONS The economic burden of influenza-related hospitalizations remains substantial, driven by underlying conditions, MV/ICU usage and secondary complications.
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Domnich A, Orsi A, Signori A, Chironna M, Manini I, Napoli C, Rizzo C, Panatto D, Icardi G. Waning intra-season vaccine effectiveness against influenza A(H3N2) underlines the need for more durable protection. Expert Rev Vaccines 2024; 23:380-388. [PMID: 38494919 DOI: 10.1080/14760584.2024.2331073] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/11/2024] [Accepted: 03/12/2024] [Indexed: 03/19/2024]
Abstract
BACKGROUND The question of whether influenza vaccine effectiveness (VE) wanes over the winter season is still open and some contradictory findings have been reported. This study investigated the possible decline in protection provided by the available influenza vaccines. RESEARCH DESIGN AND METHODS An individual-level pooled analysis of six test-negative case-control studies conducted in Italy between the 2018/2019 and 2022/2023 seasons was performed. Multivariable logistic regression analyses were performed to estimate weekly change in the odds of testing positive for influenza 14 days after vaccination. RESULTS Of 6490 patients included, 1633 tested positive for influenza. Each week that had elapsed since vaccination was associated with an increase in the odds of testing positive for any influenza (4.9%; 95% CI: 2.0-8.0%) and for A(H3N2) (6.5%; 95% CI: 2.9-10.3%). This decline in VE was, however, significant only in children and older adults. A similar increase in the odds of testing positive was seen when the dataset was restricted to vaccinees only. Conversely, VE waning was less evident for A(H1N1)pdm09 or B strains. CONCLUSIONS Significant waning of VE, especially against influenza A(H3N2), may be one of the factors associated with suboptimal end-of-season VE. Next-generation vaccines should provide more durable protection against A(H3N2).
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Affiliation(s)
- Alexander Domnich
- Hygiene Unit, San Martino Policlinico Hospital - IRCCS for Oncology and Neurosciences, Genoa, Italy
| | - Andrea Orsi
- Hygiene Unit, San Martino Policlinico Hospital - IRCCS for Oncology and Neurosciences, Genoa, Italy
- Department of Health Sciences (DISSAL), University of Genoa, Genoa, Italy
- Interuniversity Research Centre on Influenza and Other Transmissible Infections (CIRI-IT), Genoa, Italy
| | - Alessio Signori
- Department of Health Sciences (DISSAL), University of Genoa, Genoa, Italy
| | - Maria Chironna
- Interdisciplinary Department of Medicine, University of Bari, Bari, Italy
| | - Ilaria Manini
- Interuniversity Research Centre on Influenza and Other Transmissible Infections (CIRI-IT), Genoa, Italy
- Department of Molecular and Developmental Medicine, University of Siena, Siena, Italy
| | | | - Caterina Rizzo
- Department of Translational Research and New Technologies in Medicine and Surgery, University of Pisa, Pisa, Italy
| | - Donatella Panatto
- Department of Health Sciences (DISSAL), University of Genoa, Genoa, Italy
- Interuniversity Research Centre on Influenza and Other Transmissible Infections (CIRI-IT), Genoa, Italy
| | - Giancarlo Icardi
- Hygiene Unit, San Martino Policlinico Hospital - IRCCS for Oncology and Neurosciences, Genoa, Italy
- Department of Health Sciences (DISSAL), University of Genoa, Genoa, Italy
- Interuniversity Research Centre on Influenza and Other Transmissible Infections (CIRI-IT), Genoa, Italy
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Kolosova NP, Boldyrev ND, Svyatchenko SV, Danilenko AV, Goncharova NI, Shadrinova KN, Danilenko EI, Onkhonova GS, Kosenko MN, Antonets ME, Susloparov IM, Ilyicheva TN, Marchenko VY, Ryzhikov AB. An Investigation of Severe Influenza Cases in Russia during the 2022-2023 Epidemic Season and an Analysis of HA-D222G/N Polymorphism in Newly Emerged and Dominant Clade 6B.1A.5a.2a A(H1N1)pdm09 Viruses. Pathogens 2023; 13:1. [PMID: 38276147 PMCID: PMC10819184 DOI: 10.3390/pathogens13010001] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/29/2023] [Revised: 12/15/2023] [Accepted: 12/16/2023] [Indexed: 01/27/2024] Open
Abstract
In Russia, during the COVID-19 pandemic, a decrease in influenza circulation was initially observed. Influenza circulation re-emerged with the dominance of new clades of A(H3N2) viruses in 2021-2022 and A(H1N1)pdm09 viruses in 2022-2023. In this study, we aimed to characterize influenza viruses during the 2022-2023 season in Russia, as well as investigate A(H1N1)pdm09 HA-D222G/N polymorphism associated with increased disease severity. PCR testing of 780 clinical specimens showed 72.2% of them to be positive for A(H1N1)pdm09, 2.8% for A(H3N2), and 25% for influenza B viruses. The majority of A(H1N1)pdm09 viruses analyzed belonged to the newly emerged 6B.1A.5a.2a clade. The intra-sample predominance of HA-D222G/N virus variants was observed in 29% of the specimens from A(H1N1)pdm09 fatal cases. The D222N polymorphic variant was registered more frequently than D222G. All the B/Victoria viruses analyzed belonged to the V1A.3a.2 clade. Several identified A(H3N2) viruses belonged to one of the four subclades (2a.1b, 2a.3a.1, 2a.3b, 2b) within the 3C.2a1b.2a.2 group. The majority of antigenically characterized viruses bore similarities to the corresponding 2022-2023 NH vaccine strains. Only one influenza A(H1N1)pdm09 virus showed reduced inhibition by neuraminidase inhibitors. None of the influenza viruses analyzed had genetic markers of reduced susceptibility to baloxavir.
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