RETHINKING THE DEAD-END: A REVIEW OF HUMAN-TO HUMAN HANTAVIRUS TRANSMISSION

Abstract

Background: Hantaviruses have long been classified as strictly rodent-borne zoonotic pathogens, with humans serving as incidental, dead-end hosts. However, outbreaks of Andes virus (ANDV) in South America challenge this uniform paradigm, presenting clear evidence of person-to-person transmissibility. Objective: This narrative review synthesizes the epidemiological, clinical, and molecular evidence surrounding human-to-human hantavirus transmission, highlighting the biological dichotomy between strictly zoonotic lineages and transmissible strains. Methodology: A comprehensive search of PubMed/MEDLINE, Scopus, Web of Science, and Google Scholar was conducted for literature published between 1990 and 2026. Studies focusing on outbreak investigations, cohort surveillance, case series, and molecular phylogenetics of clinically significant hantaviruses (including Hantaan, Puumala, Sin Nombre, and Andes viruses) were reviewed and analyzed narratively. Results: The literature demonstrates a definitive, lineage-dependent separation in transmission potential. Old World hantaviruses (e.g., Hantaan, Puumala) and the New World Sin Nombre virus show an absolute absence of confirmed interhuman transmission, even in high-risk nosocomial or close household settings. Conversely, Andes virus demonstrates reproducible secondary transmission, primarily confined to close family contacts, intimate partners, and specific healthcare scenarios involving aerosol-generating procedures. Molecular sequencing confirms directional transmission via identical viral genomic segments within ANDV clusters. However, all hantavirus transmission chains remain short, with an estimated reproductive number (R_0) below 1.0, indicating a lack of sustained epidemic potential. Conclusion: Hantavirus transmission is a strain-dependent process. While the majority of lineages remain strictly zoonotic, Andes virus represents a distinct exception capable of short-chain, human-to-human propagation under high-contact conditions. These findings underscore the need for targeted infection-control protocols and risk stratified public health responses.