Influenza

Influenza is a viral disease described in the payload as seasonal flu and mapped to ICD-10 J09-J11 and ICD-11 1E30 ^[1]. The source set available here does not provide a fuller etiologic characterization such as subtype distribution, lineage names, or virologic persistence, so those details are not added beyond the provided metadata ^[1][2][5][6]. The evidence base supplied for this entry is largely focused on vaccination and post-exposure prophylaxis, which is relevant to public-health interpretation but does not substitute for a complete disease description ^[1][3][4].

The supplied snippets do not describe the clinical syndrome, symptom pattern, severity spectrum, course, or complications of influenza in a way that can be safely summarized without inference, so source-backed clinical detail is not yet available ^[1][3][4]. The vaccine effectiveness review does, however, indicate that influenza is a laboratory-confirmed clinical outcome used in trials, including confirmation by RT-PCR or culture ^[3]. Beyond that, the provided sources do not support statements about duration, hospitalization risk, or complication patterns, and those elements are therefore omitted ^[3][4].

The only epidemiologic framing in the supplied materials is that influenza is seasonal and that annual vaccination is recommended in the United States for persons aged 6 months and older who do not have contraindications ^[1]. The sources do not provide geographic distribution beyond the U.S. vaccination guidance context, nor do they supply outbreak histories, reservoir ecology, or burden estimates for routine surveillance interpretation ^[1][3][4]. A systematic review cited in the payload screened 5,707 articles and included 31 eligible studies, which reflects the breadth of the evidence base on vaccine efficacy rather than disease incidence itself ^[3]. No additional epidemiologic detail is supported by the snippets provided ^[1][3][4].

The supplied sources do not explicitly state the route of transmission or exposure mechanism for influenza, so source-backed transmission detail is not yet available ^[1][3][4]. They do show that antiviral post-exposure prophylaxis has been studied, indicating that post-exposure prevention is a relevant public-health concept for this infection ^[4]. However, the mechanism by which exposure occurs is not described in the evidence provided, and no further transmission claims are added ^[4].

The sources identify several groups for which vaccine guidance differs or is specifically highlighted: all persons aged 6 months and older without contraindications are included in routine annual vaccination recommendations, adults aged 65 years and older have preferential vaccine options, and solid organ transplant recipients aged 18 through 64 years receiving immunosuppressive medication regimens may receive specified higher-dose or adjuvanted products ^[1]. The vaccine meta-analysis also reports age-stratified efficacy data, including adults aged 18 to 65 years and children aged 6 months to 7 years, but it does not by itself define biological risk groups for disease severity ^[3]. Beyond these source-backed categories, additional high-risk groups are not specified in the provided snippets ^[1][3].

Prevention in the supplied sources is centered on routine annual influenza vaccination, which ACIP recommends for all persons aged 6 months and older who do not have contraindications ^[1]. The 2024-25 guidance notes that age-appropriate influenza vaccines should be used, with preferential vaccine options stated for adults aged 65 years and older and acceptable higher-dose or adjuvanted options for certain solid organ transplant recipients receiving immunosuppressive regimens ^[1]. A separate systematic review found that antiviral post-exposure prophylaxis with neuraminidase inhibitors can reduce the incidence of influenza and symptomatic influenza, although the efficacy of other antiviral classes remains unclear ^[4].

For surveillance purposes, the key takeaways from the supplied sources are that influenza is monitored as a seasonal viral illness and that prevention guidance is updated annually, which can affect interpretation of observed trends over time ^[1]. The meta-analysis also shows that influenza vaccine performance has been evaluated using RT-PCR or culture-confirmed outcomes, underscoring the importance of laboratory confirmation when comparing data across studies or seasons ^[3]. The current source set does not provide outbreak thresholds, laboratory case definitions, or burden metrics, so those elements are not yet available from the supplied material ^[1][3][4].

1. 1 Grohskopf LA et al. Prevention and Control of Seasonal Influenza with Vaccines: Recommendations of the Advisory Committee on Immunization Practices - United States, 2024-25 Influenza Season. MMWR Recomm Rep. 2024 Aug 29. PMID: 39197095. doi: 10.15585/mmwr.rr7305a1. PubMed: https://pubmed.ncbi.nlm.nih.gov/39197095/
2. 2 Influenza Influenza. DGPI Handbuch. 2026. doi: 10.1055/f-0005-0044-b000000868. DOI: https://doi.org/10.1055/f-0005-0044-b000000868
3. 3 Osterholm MT et al. Efficacy and effectiveness of influenza vaccines: a systematic review and meta-analysis. Lancet Infect Dis. 2012 Jan. PMID: 22032844. doi: 10.1016/S1473-3099(11)70295-X. PubMed: https://pubmed.ncbi.nlm.nih.gov/22032844/
4. 4 Zhao Y et al. Antivirals for post-exposure prophylaxis of influenza: a systematic review and network meta-analysis. Lancet. 2024 Aug 24. PMID: 39181596. doi: 10.1016/S0140-6736(24)01357-6. PubMed: https://pubmed.ncbi.nlm.nih.gov/39181596/
5. 5 Influenza. Der Internist. 2019. doi: 10.1007/s00108-019-00670-6. DOI: https://doi.org/10.1007/s00108-019-00670-6
6. 6 Influenza. Der Internist. 2021. doi: 10.1007/s00108-021-01101-1. DOI: https://doi.org/10.1007/s00108-021-01101-1

ICD-10

J09-J11

ICD-11

1E30

Total cases

73.5M

Total deaths

953

Peak month

2025-12

Coverage

4 reporting countries · 2000-01-01 → 2026-06-20