Intratumoral bacteria are increasingly recognized as integral and dynamic components of the tumor microenvironment (TME), with profound implications for tumor initiation, progression, metastasis, immune remodeling, and therapeutic response. These microorganisms may originate from mucosal barrier breaches, hematogenous or lymphatic dissemination, local migration from adjacent tissues, or co‐migration with metastatic cells, and can be characterized by sequencing‐based, imaging, culture‐dependent, and multi‐omics approaches. Accumulating evidence indicates that intratumoral bacteria contribute to tumorigenesis by inducing genomic instability, DNA damage, epigenetic alterations, oncogenic signaling, and chronic inflammation. Beyond primary tumor growth, they participate in multiple steps of the metastatic cascade, including epithelial–mesenchymal transition, cytoskeletal remodeling, invasion, intravasation, extravasation, pre‐metastatic niche formation, angiogenesis, and distant colonization. Intratumoral bacteria also reshape immune and non‐immune compartments of the TME, exerting dual effects by promoting immune suppression or enhancing antitumor immunity depending on bacterial species, tumor context, and host immune status. In this review, we summarize the historical development, methodological advances, cancer‐type‐specific diversity, and mechanistic roles of intratumoral microbiota in tumor progression and metastasis. We further discuss their diagnostic and prognostic value, as well as their therapeutic implications for conventional anticancer treatments and microbiota‐targeted strategies, highlighting opportunities and challenges for microbiota‐guided precision oncology.

Hepatitis E virus (HEV) infection typically presents as a self-limiting acute hepatitis, but a subset of patients may progress to severe hepatitis, with po

Hepatitis E virus (HEV) is a major global health concern, evolving from a self-limited enteric infection to a complex systemic disease with an expanding burden. This narrative review synthesizes current evidence on HEV virology, epidemiology, zoonotic transmission, and clinical manifestations to inform clinicians, researchers, and policymakers. Despite substantial morbidity among pregnant women and immunosuppressed patients, HEV awareness remains limited, and therapeutic options are constrained. Four genotypes (1–4) show distinct epidemiological patterns; chronic infection occurs primarily in immunocompromised hosts, while extrahepatic manifestations, including neurological and renal complications, are increasingly recognized. Treatment remains limited to ribavirin with variable efficacy and contraindications. The HEV-239 vaccine demonstrates sustained efficacy but requires broader implementation. This review integrates recent advances across virology, clinical practice, and public health, offering a unified framework for understanding HEV as a systemic disease requiring enhanced surveillance, targeted antiviral development, and expanded vaccine deployment within a “One Health” framework.