{ "schemaVersion": "BASE-biological-assertion/1.1.0", "caseStudy": { "slug": "hantavirus-el-nino", "title": "Hantavirus, Rainfall, and Ecosystem Change" }, "context": { "scope": "Deer mouse–Sin Nombre virus–human system; ecological interpretation of the 1992–93 Four Corners outbreak", "organism": "North American deer mouse (Peromyscus maniculatus); human spillover is a separate host process", "taxonId": "10042", "conditionId": "disease-hantavirus-pulmonary-syndrome", "population": "Local rodent populations, infected-host prevalence, and human cases in the southwestern United States", "location": "Four Corners region / southwestern United States; evidence varies by study site", "timePeriod": "1992–1993 outbreak context, with later ecological follow-up studies", "exposureContext": "Risk requires infected reservoir hosts and human contact with contaminated excreta; rainfall is an upstream ecological correlate, not a direct cause of infection." }, "groups": [ { "id": "climate-resources", "title": "Climate & Ecological Resources", "description": "Compare the original outbreak observations with later, site-specific field studies.", "assertionIds": [ "hanta-outbreak-followed-wet-enso-period", "hanta-risk-patterns-vary-across-sites", "hanta-plant-productivity-link-is-site-dependent" ] }, { "id": "reservoir-spillover", "title": "Reservoir Host & Human Exposure", "description": "Separate virus circulation in deer mice from exposure and disease in people.", "assertionIds": [ "hanta-deer-mouse-reservoir", "hanta-virus-can-spill-over-through-excreta", "hanta-human-risk-depends-on-contact" ] }, { "id": "causal-limits", "title": "Causal Chain & Open Questions", "description": "Identify which links are measured and which remain hypotheses.", "assertionIds": [ "hanta-causal-chain-has-unresolved-links" ] } ], "assertions": [ { "id": "hanta-outbreak-followed-wet-enso-period", "version": 1, "subjectId": "concept-epidemiology", "predicate": "DOCUMENTED_ASSOCIATION_IN", "objectValue": "The 1992–93 Four Corners hantavirus pulmonary syndrome outbreak followed unusual regional El Niño-related rainfall", "statement": "An observational investigation of the 1993 Four Corners cases identified climatic and environmental patterns at probable exposure sites during a period that included unusually wet conditions associated with the 1992–93 El Niño.", "qualifier": "The case-site analysis was observational, and the authors noted uncertainty in reconstructing exposure locations and possible selection bias. It did not establish every proposed link from precipitation through plant resources, mouse abundance, viral infection, and human exposure.", "evidenceKind": "primary_study", "context": { "scope": "Deer mouse–Sin Nombre virus–human system; ecological interpretation of the 1992–93 Four Corners outbreak", "organism": "North American deer mouse (Peromyscus maniculatus); human spillover is a separate host process", "taxonId": "10042", "conditionId": "disease-hantavirus-pulmonary-syndrome", "population": "Local rodent populations, infected-host prevalence, and human cases in the southwestern United States", "location": "Four Corners region / southwestern United States; evidence varies by study site", "timePeriod": "1992–1993 outbreak context, with later ecological follow-up studies", "exposureContext": "Risk requires infected reservoir hosts and human contact with contaminated excreta; rainfall is an upstream ecological correlate, not a direct cause of infection." }, "references": [ { "referenceId": "hantavirus-climate-case-study-1999", "relation": "supports", "sourceRecordId": "PMID:10081675; PMCID:PMC2627709", "sourceVersion": "Published 1999; case and probable exposure-site analyses from 1993–1995" }, { "referenceId": "yates-hantavirus-2002", "relation": "supports", "sourceRecordId": "PMID:12473747", "sourceVersion": "Published 2002" }, { "referenceId": "openstax-hantavirus", "relation": "context", "sourceRecordId": "OpenStax Biology 2e: Hantavirus and El Niño", "sourceVersion": "Edition/version not recorded in this snapshot" } ] }, { "id": "hanta-risk-patterns-vary-across-sites", "version": 1, "subjectId": "taxon-deer-mouse", "predicate": "POPULATION_AND_INFECTION_RISK_VARY_WITH", "objectValue": "Site-level ecological conditions and their duration; 1999 crude Sin Nombre virus prevalence was higher at modeled high-risk than low-risk sites", "statement": "In a post-ENSO field study, deer-mouse captures increased at modeled high-risk sites, and crude Sin Nombre virus prevalence in 1999 was 30.8% at high-risk sites versus 8.3% at low-risk sites.", "qualifier": "These are site-level observations from a later study, not measurements of the 1993 Four Corners causal chain. The risk model and associations do not show that rainfall alone caused infection or human cases; ecology, sampling, and exposure remain distinct steps.", "evidenceKind": "primary_study", "context": { "scope": "Deer mouse–Sin Nombre virus–human system; ecological interpretation of the 1992–93 Four Corners outbreak", "organism": "North American deer mouse (Peromyscus maniculatus); human spillover is a separate host process", "taxonId": "10042", "conditionId": "disease-hantavirus-pulmonary-syndrome", "population": "Local rodent populations, infected-host prevalence, and human cases in the southwestern United States", "location": "Four Corners region / southwestern United States; evidence varies by study site", "timePeriod": "1992–1993 outbreak context, with later ecological follow-up studies", "exposureContext": "Risk requires infected reservoir hosts and human contact with contaminated excreta; rainfall is an upstream ecological correlate, not a direct cause of infection." }, "references": [ { "referenceId": "yates-hantavirus-2002", "relation": "supports", "sourceRecordId": "PMID:12473747", "sourceVersion": "Published 2002; post-ENSO field observations and modeled high-/low-risk sites" }, { "referenceId": "deer-mouse-rainfall-2018", "relation": "qualifies", "sourceRecordId": "PMID:29299286", "sourceVersion": "Published 2018; six Montana sites, lagged resource–abundance correlations at three" } ] }, { "id": "hanta-plant-productivity-link-is-site-dependent", "version": 1, "subjectId": "concept-epidemiology", "predicate": "ECOLOGICAL_RESOURCE_LINK_VARIES_BY_SITE", "objectValue": "Plant productivity and deer-mouse abundance were positively correlated with a lag at three of six studied Montana sites", "statement": "Later field work found that precipitation-linked plant productivity predicted deer-mouse abundance with a several-month lag at three of six study sites, with weaker effects when mouse populations were already larger.", "qualifier": "This study was conducted in central and western Montana, not the 1993 Four Corners outbreak; it demonstrates site dependence rather than directly explaining that outbreak.", "evidenceKind": "primary_study", "context": { "scope": "Deer mouse–Sin Nombre virus–human system; ecological interpretation of the 1992–93 Four Corners outbreak", "organism": "North American deer mouse (Peromyscus maniculatus); human spillover is a separate host process", "taxonId": "10042", "conditionId": "disease-hantavirus-pulmonary-syndrome", "population": "Local rodent populations, infected-host prevalence, and human cases in the southwestern United States", "location": "Four Corners region / southwestern United States; evidence varies by study site", "timePeriod": "1992–1993 outbreak context, with later ecological follow-up studies", "exposureContext": "Risk requires infected reservoir hosts and human contact with contaminated excreta; rainfall is an upstream ecological correlate, not a direct cause of infection." }, "references": [ { "referenceId": "deer-mouse-rainfall-2018", "relation": "qualifies", "sourceRecordId": "PMID:29299286", "sourceVersion": "Published 2018; six Montana sites" } ] }, { "id": "hanta-deer-mouse-reservoir", "version": 1, "subjectId": "taxon-deer-mouse", "predicate": "RESERVOIR_HOST_FOR", "objectId": "taxon-sin-nombre-virus", "statement": "North American deer mice are an important reservoir host for Sin Nombre virus in the United States.", "qualifier": "Reservoir status does not mean every deer mouse is infected; prevalence varies with place, time, host population, and sampling method.", "evidenceKind": "database_annotation", "context": { "scope": "Deer mouse–Sin Nombre virus–human system; ecological interpretation of the 1992–93 Four Corners outbreak", "organism": "North American deer mouse (Peromyscus maniculatus); human spillover is a separate host process", "taxonId": "10042", "conditionId": "disease-hantavirus-pulmonary-syndrome", "population": "Local rodent populations, infected-host prevalence, and human cases in the southwestern United States", "location": "Four Corners region / southwestern United States; evidence varies by study site", "timePeriod": "1992–1993 outbreak context, with later ecological follow-up studies", "exposureContext": "Risk requires infected reservoir hosts and human contact with contaminated excreta; rainfall is an upstream ecological correlate, not a direct cause of infection." }, "references": [ { "referenceId": "ncbi-deer-mouse", "relation": "context", "sourceRecordId": "NCBI Taxonomy:10042", "sourceVersion": "Record accessed 2026-09-27" }, { "referenceId": "cdc-hantavirus", "relation": "supports", "sourceRecordId": "CDC MMWR: Hantavirus Pulmonary Syndrome", "sourceVersion": "Page version not recorded in this snapshot" } ] }, { "id": "hanta-virus-can-spill-over-through-excreta", "version": 1, "subjectId": "taxon-sin-nombre-virus", "predicate": "CAN_EXPOSE_HUMANS_THROUGH", "objectId": "disease-hantavirus-pulmonary-syndrome", "statement": "People can acquire Sin Nombre virus after inhaling aerosolized material contaminated by infected deer-mouse urine, droppings, or saliva.", "qualifier": "This describes a recognized exposure route; infection requires exposure to infectious material, and human-to-human transmission is not the ordinary route for Sin Nombre virus.", "evidenceKind": "clinical_guideline", "context": { "scope": "Deer mouse–Sin Nombre virus–human system; ecological interpretation of the 1992–93 Four Corners outbreak", "organism": "North American deer mouse (Peromyscus maniculatus); human spillover is a separate host process", "taxonId": "10042", "conditionId": "disease-hantavirus-pulmonary-syndrome", "population": "Local rodent populations, infected-host prevalence, and human cases in the southwestern United States", "location": "Four Corners region / southwestern United States; evidence varies by study site", "timePeriod": "1992–1993 outbreak context, with later ecological follow-up studies", "exposureContext": "Risk requires infected reservoir hosts and human contact with contaminated excreta; rainfall is an upstream ecological correlate, not a direct cause of infection." }, "references": [ { "referenceId": "cdc-hantavirus", "relation": "supports", "sourceRecordId": "CDC MMWR: Hantavirus Pulmonary Syndrome", "sourceVersion": "Page version not recorded in this snapshot" }, { "referenceId": "hantavirus-mechanistic-2016", "relation": "supports", "sourceRecordId": "PMID:26955081", "sourceVersion": "Published 2016" } ] }, { "id": "hanta-human-risk-depends-on-contact", "version": 1, "subjectId": "disease-hantavirus-pulmonary-syndrome", "predicate": "RISK_DEPENDS_ON", "objectValue": "Rodent infection and shedding, host activity, peridomestic contact, human behavior, and environmental conditions", "statement": "Human disease risk depends on the encounter between infected reservoir hosts and people, including where rodents move and whether activities aerosolize contaminated material.", "qualifier": "Rodent abundance alone is not sufficient to predict human cases; housing, behavior, seasonal activity, viral prevalence, and case ascertainment also matter.", "evidenceKind": "mechanistic_review", "context": { "scope": "Deer mouse–Sin Nombre virus–human system; ecological interpretation of the 1992–93 Four Corners outbreak", "organism": "North American deer mouse (Peromyscus maniculatus); human spillover is a separate host process", "taxonId": "10042", "conditionId": "disease-hantavirus-pulmonary-syndrome", "population": "Local rodent populations, infected-host prevalence, and human cases in the southwestern United States", "location": "Four Corners region / southwestern United States; evidence varies by study site", "timePeriod": "1992–1993 outbreak context, with later ecological follow-up studies", "exposureContext": "Risk requires infected reservoir hosts and human contact with contaminated excreta; rainfall is an upstream ecological correlate, not a direct cause of infection." }, "references": [ { "referenceId": "hantavirus-mechanistic-2016", "relation": "supports", "sourceRecordId": "PMID:26955081", "sourceVersion": "Published 2016" } ] }, { "id": "hanta-causal-chain-has-unresolved-links", "version": 1, "subjectId": "concept-epidemiology", "predicate": "ECOLOGICAL_CAUSAL_CHAIN_REQUIRES", "objectValue": "Longitudinal evidence linking climate, resources, host abundance and infection, host movement, human exposure, and cases", "statement": "The proposed climate-to-human-disease chain contains links that remain incompletely measured, especially connections among reservoir behavior, virus transmission, and human exposure.", "qualifier": "This case is best used to compare a mechanistic hypothesis with field data, not as a deterministic rule that wet years produce outbreaks.", "evidenceKind": "mechanistic_review", "context": { "scope": "Deer mouse–Sin Nombre virus–human system; ecological interpretation of the 1992–93 Four Corners outbreak", "organism": "North American deer mouse (Peromyscus maniculatus); human spillover is a separate host process", "taxonId": "10042", "conditionId": "disease-hantavirus-pulmonary-syndrome", "population": "Local rodent populations, infected-host prevalence, and human cases in the southwestern United States", "location": "Four Corners region / southwestern United States; evidence varies by study site", "timePeriod": "1992–1993 outbreak context, with later ecological follow-up studies", "exposureContext": "Risk requires infected reservoir hosts and human contact with contaminated excreta; rainfall is an upstream ecological correlate, not a direct cause of infection." }, "references": [ { "referenceId": "hantavirus-mechanistic-2016", "relation": "supports", "sourceRecordId": "PMID:26955081", "sourceVersion": "Published 2016" }, { "referenceId": "deer-mouse-rainfall-2018", "relation": "qualifies", "sourceRecordId": "PMID:29299286", "sourceVersion": "Published 2018; site-dependent lagged associations" } ] } ], "limitation": "The climate-to-human-disease pathway is a proposed ecological chain, not a deterministic forecast. Studies differ in geography and methods, plant-resource effects vary by site, and unresolved links remain between host ecology, viral transmission, and actual human exposure.", "release": { "snapshotSchemaVersion": "BASE-case-snapshot/1.0.0", "exportedAt": "2026-10-11T01:52:17.383Z", "caseContentRevision": 1, "diagramRevision": 1, "diagramId": "hantavirus-ecosystem-case-map", "sourceCommitSha": "e97dc5327f9d807ecaf44b77e87ddf6f3f6d2bc2", "snapshotSha256": "b4311643b53042ecee53f670eb8cf4395fa86bef10ad957b998d52728bae7806" }, "snapshot": { "releaseInputs": { "caseContentRevision": 1, "diagramRevision": 1, "diagramId": "hantavirus-ecosystem-case-map", "sourceCommitSha": "e97dc5327f9d807ecaf44b77e87ddf6f3f6d2bc2" }, "caseStudy": { "slug": "hantavirus-el-nino", "title": "Hantavirus, Rainfall, and Ecosystem Change", "area": "Ecology · Microbiology · Human Health", "question": "How could changing rainfall affect the risk of a disease carried by wildlife?", "overview": "The 1992–93 Four Corners hantavirus pulmonary syndrome outbreak prompted a hypothesis connecting unusual El Niño-related rainfall to vegetation, deer-mouse populations, virus circulation, and human exposure. The sequence is useful because each link can be tested—and the links do not all have the same strength of evidence.", "mechanism": [ "Investigators studying the 1993 Four Corners cases found climatic and environmental patterns at probable exposure sites during a period that included unusually wet El Niño-related conditions. This was an observational clue, not proof of a complete causal chain.", "In the Four Corners case, ecological observations motivated a bottom-up hypothesis: more resources might support a change in deer-mouse abundance. Later field work found lagged resource–mouse correlations at only some study sites, so the link is not universal.", "In a later post-ENSO field study, crude Sin Nombre virus prevalence in 1999 was 30.8% at modeled high-risk sites and 8.3% at low-risk sites. This supports geographic variation in reservoir infection, not a direct estimate of human risk or proof that rainfall caused it.", "North American deer mice are an important reservoir host for Sin Nombre virus, but abundance is not the same as infection prevalence; many mice may be uninfected, and both variables vary by place and time.", "Virus circulation among reservoir hosts is a separate step from spillover. Infected rodents can shed virus in urine, droppings, or saliva.", "People can be exposed when contaminated material is disturbed and inhaled or contacted. Housing, rodent activity, cleanup behavior, season, and other factors influence whether that encounter occurs.", "Human hantavirus pulmonary syndrome follows infection in a susceptible person, but case risk cannot be inferred from rainfall or rodent counts alone.", "The full climate-to-disease chain remains a mechanistic hypothesis with incompletely measured links, especially host movement, viral transmission, and human exposure." ], "evidence": "The El Niño narrative is a hypothesis built from evidence collected in different places, years, and study designs. Climate–resource–host links vary by site, reservoir abundance is distinct from infection prevalence, and human disease requires exposure to infectious material; rainfall alone does not cause an outbreak.", "entityIds": [ "taxon-deer-mouse", "taxon-sin-nombre-virus", "disease-hantavirus-pulmonary-syndrome", "concept-epidemiology", "concept-pathogen" ], "references": [ "openstax-hantavirus", "cdc-hantavirus", "ncbi-deer-mouse", "ncbi-sin-nombre", "hantavirus-climate-case-study-1999", "yates-hantavirus-2002", "hantavirus-mechanistic-2016", "deer-mouse-rainfall-2018" ], "assertionIds": [ "hanta-outbreak-followed-wet-enso-period", "hanta-risk-patterns-vary-across-sites", "hanta-plant-productivity-link-is-site-dependent", "hanta-deer-mouse-reservoir", "hanta-virus-can-spill-over-through-excreta", "hanta-human-risk-depends-on-contact", "hanta-causal-chain-has-unresolved-links" ], "check": [ { "question": "Why is this case about more than the virus itself?", "answer": "Disease risk can depend on interactions among climate, plants, animal populations, viral infection, and human exposure." }, { "question": "Does a wet year automatically cause a hantavirus outbreak?", "answer": "No. It may change ecological conditions, but transmission and human disease also depend on many other factors." }, { "question": "Why is the resource-to-deer-mouse link not treated as a universal rule?", "answer": "A later study found a lagged correlation at three of six Montana sites, and effects weakened when mouse populations were already larger. This is evidence for site-dependent dynamics, not a direct measurement of the 1993 Four Corners event." }, { "question": "What does the high-risk versus low-risk site comparison show?", "answer": "The later study measured higher crude Sin Nombre virus prevalence at modeled high-risk sites than at low-risk sites in 1999 (30.8% versus 8.3%). That is a site-level association from a later field study; it does not prove that rainfall caused human cases in 1993." }, { "question": "What has to happen between more deer mice and a human case?", "answer": "Rodents must be infected and shed virus, a person must encounter infectious material, and exposure must lead to infection and disease. Each step depends on additional conditions." } ] }, "diagram": { "revision": 1, "id": "hantavirus-ecosystem-case-map", "title": "From unusual rain to possible human exposure", "subtitle": "The 1992–93 southwestern US case links climate, food, wildlife, pathogens, and people.", "note": "OpenStax describes a specific historical association: wet El Niño weather increased pinyon-nut production and deer-mouse numbers during the 1992–93 Sin Nombre virus outbreak. This does not mean rainfall alone causes disease. Infection risk depends on infected rodents, human exposure, housing, behavior, and other conditions. People can be exposed when rodent urine, droppings, or saliva contaminate air or surfaces.", "sources": [ { "label": "OpenStax Biology 2e · Ecosystem case", "href": "https://openstax.org/books/biology-2e/pages/46-introduction" }, { "label": "CDC · About hantavirus", "href": "https://www.cdc.gov/hantavirus/about/" } ], "lanes": [ { "label": "Historical outbreak context", "note": "An observed timing and climate association; rainfall alone does not establish a causal chain.", "links": [ "was documented during a period including" ], "assertionIds": [ "hanta-outbreak-followed-wet-enso-period" ], "nodes": [ { "label": "1993 Four Corners HPS cases", "detail": "Investigators noted climate and environmental patterns at probable exposure sites.", "href": "/concept/epidemiology" }, { "label": "Unusually wet 1992–93 El Niño conditions", "detail": "This temporal association motivates the case question; it is not proof that rainfall caused human cases." } ] }, { "label": "Site-dependent ecological evidence", "note": "A later field study in Montana found the lagged association at only three of six sites.", "links": [ "showed a lagged, site-limited association with" ], "assertionIds": [ "hanta-plant-productivity-link-is-site-dependent" ], "nodes": [ { "label": "Precipitation-linked plant productivity", "detail": "Resource availability was measured in later field work at several sites." }, { "label": "Deer mouse abundance", "detail": "Abundance tracked plant productivity with a lag at some sites; this is not a universal rule.", "href": "/taxon/deer-mouse" } ] }, { "label": "Reservoir host", "note": "Host abundance and virus prevalence are separate measurements.", "links": [ "is an important reservoir host for" ], "assertionIds": [ "hanta-deer-mouse-reservoir" ], "nodes": [ { "label": "North American deer mouse", "detail": "Not every individual mouse carries the virus.", "href": "/taxon/deer-mouse" }, { "label": "Sin Nombre virus", "detail": "A hantavirus associated with deer mice in the United States.", "href": "/taxon/sin-nombre-virus" } ] }, { "label": "Spillover route", "note": "Virus circulation is separate from human exposure and disease.", "links": [ "can expose people through infected-rodent excreta associated with" ], "assertionIds": [ "hanta-virus-can-spill-over-through-excreta" ], "nodes": [ { "label": "Sin Nombre virus", "detail": "Virus may be present in contaminated rodent urine, droppings, or saliva.", "href": "/taxon/sin-nombre-virus" }, { "label": "Hantavirus pulmonary syndrome", "detail": "People can be infected after inhaling aerosolized contaminated material; actual risk depends on contact and setting.", "href": "/disease/hantavirus-pulmonary-syndrome" } ] }, { "label": "Human disease limits", "note": "Disease risk depends on more than the presence of deer mice or a wet year.", "links": [ "risk depends on" ], "assertionIds": [ "hanta-human-risk-depends-on-contact" ], "nodes": [ { "label": "Hantavirus pulmonary syndrome risk", "detail": "Infection and disease require an exposure route and a susceptible person.", "href": "/disease/hantavirus-pulmonary-syndrome" }, { "label": "Rodent infection, shedding, and human contact", "detail": "Rodent activity, housing, behavior, and environmental conditions affect the chance of encounter." } ] } ] }, "connectedRecords": [ { "id": "taxon-deer-mouse", "type": "taxon", "slug": "deer-mouse", "name": "North American deer mouse", "canonicalName": "North American deer mouse", "summary": "Peromyscus maniculatus, a rodent that serves as an important reservoir host for Sin Nombre virus in the United States." }, { "id": "taxon-sin-nombre-virus", "type": "taxon", "slug": "sin-nombre-virus", "name": "Orthohantavirus sinnombreense", "canonicalName": "Orthohantavirus sinnombreense", "summary": "A hantavirus species whose reservoir in the United States is chiefly the deer mouse and that can cause hantavirus pulmonary syndrome." }, { "id": "disease-hantavirus-pulmonary-syndrome", "type": "disease", "slug": "hantavirus-pulmonary-syndrome", "name": "Hantavirus Pulmonary syndrome", "canonicalName": "Hantavirus pulmonary syndrome", "summary": "A severe respiratory illness associated with infection by New World hantaviruses, including Sin Nombre virus in the United States." }, { "id": "concept-epidemiology", "type": "concept", "slug": "epidemiology", "name": "Epidemiology", "canonicalName": "Epidemiology", "summary": "Study of how health events are distributed in populations and what factors influence them." }, { "id": "concept-pathogen", "type": "concept", "slug": "pathogen", "name": "Pathogen", "canonicalName": "Pathogen", "summary": "A biological agent that can cause disease in a host under particular conditions." } ], "references": [ { "id": "openstax-hantavirus", "title": "Ecology of Ecosystems: Hantavirus and El Niño", "publisher": "OpenStax Biology 2e", "url": "https://openstax.org/books/biology-2e/pages/46-introduction", "kind": "textbook" }, { "id": "cdc-hantavirus", "title": "Hantavirus Pulmonary Syndrome", "publisher": "CDC MMWR", "url": "https://www.cdc.gov/mmwr/preview/mmwrhtml/00001759.htm", "kind": "article" }, { "id": "ncbi-deer-mouse", "title": "Peromyscus maniculatus (Taxonomy ID 10042)", "publisher": "NCBI Taxonomy", "url": "https://www.ncbi.nlm.nih.gov/datasets/taxonomy/10042/", "kind": "database" }, { "id": "ncbi-sin-nombre", "title": "Orthohantavirus sinnombreense (Taxonomy ID 3052499)", "publisher": "NCBI Taxonomy", "url": "https://www.ncbi.nlm.nih.gov/taxonomy/3052499", "kind": "database" }, { "id": "hantavirus-climate-case-study-1999", "title": "Climatic and environmental patterns associated with hantavirus pulmonary syndrome, Four Corners region, United States", "publisher": "Engelthaler et al. · PMID 10081675", "url": "https://pubmed.ncbi.nlm.nih.gov/10081675/", "kind": "article" }, { "id": "yates-hantavirus-2002", "title": "Satellite imagery characterizes local animal reservoir populations of Sin Nombre virus in the southwestern United States", "publisher": "Yates et al. · PMID 12473747", "url": "https://pubmed.ncbi.nlm.nih.gov/12473747/", "kind": "article" }, { "id": "hantavirus-mechanistic-2016", "title": "Toward a Mechanistic Understanding of Environmentally Forced Zoonotic Disease Emergence: Sin Nombre Hantavirus", "publisher": "Luis et al. · PMID 26955081", "url": "https://pubmed.ncbi.nlm.nih.gov/26955081/", "kind": "article" }, { "id": "deer-mouse-rainfall-2018", "title": "A damped precipitation-driven, bottom-up model for deer mouse population abundance in the northwestern United States", "publisher": "Luis et al. · PMID 29299286", "url": "https://pubmed.ncbi.nlm.nih.gov/29299286/", "kind": "article" } ], "mechanismEvidence": { "schemaVersion": "BASE-biological-assertion/1.1.0", "context": { "scope": "Deer mouse–Sin Nombre virus–human system; ecological interpretation of the 1992–93 Four Corners outbreak", "organism": "North American deer mouse (Peromyscus maniculatus); human spillover is a separate host process", "taxonId": "10042", "conditionId": "disease-hantavirus-pulmonary-syndrome", "population": "Local rodent populations, infected-host prevalence, and human cases in the southwestern United States", "location": "Four Corners region / southwestern United States; evidence varies by study site", "timePeriod": "1992–1993 outbreak context, with later ecological follow-up studies", "exposureContext": "Risk requires infected reservoir hosts and human contact with contaminated excreta; rainfall is an upstream ecological correlate, not a direct cause of infection." }, "groups": [ { "id": "climate-resources", "title": "Climate & Ecological Resources", "description": "Compare the original outbreak observations with later, site-specific field studies.", "assertionIds": [ "hanta-outbreak-followed-wet-enso-period", "hanta-risk-patterns-vary-across-sites", "hanta-plant-productivity-link-is-site-dependent" ] }, { "id": "reservoir-spillover", "title": "Reservoir Host & Human Exposure", "description": "Separate virus circulation in deer mice from exposure and disease in people.", "assertionIds": [ "hanta-deer-mouse-reservoir", "hanta-virus-can-spill-over-through-excreta", "hanta-human-risk-depends-on-contact" ] }, { "id": "causal-limits", "title": "Causal Chain & Open Questions", "description": "Identify which links are measured and which remain hypotheses.", "assertionIds": [ "hanta-causal-chain-has-unresolved-links" ] } ], "assertions": [ { "id": "hanta-outbreak-followed-wet-enso-period", "version": 1, "subjectId": "concept-epidemiology", "predicate": "DOCUMENTED_ASSOCIATION_IN", "objectValue": "The 1992–93 Four Corners hantavirus pulmonary syndrome outbreak followed unusual regional El Niño-related rainfall", "statement": "An observational investigation of the 1993 Four Corners cases identified climatic and environmental patterns at probable exposure sites during a period that included unusually wet conditions associated with the 1992–93 El Niño.", "qualifier": "The case-site analysis was observational, and the authors noted uncertainty in reconstructing exposure locations and possible selection bias. It did not establish every proposed link from precipitation through plant resources, mouse abundance, viral infection, and human exposure.", "evidenceKind": "primary_study", "context": { "scope": "Deer mouse–Sin Nombre virus–human system; ecological interpretation of the 1992–93 Four Corners outbreak", "organism": "North American deer mouse (Peromyscus maniculatus); human spillover is a separate host process", "taxonId": "10042", "conditionId": "disease-hantavirus-pulmonary-syndrome", "population": "Local rodent populations, infected-host prevalence, and human cases in the southwestern United States", "location": "Four Corners region / southwestern United States; evidence varies by study site", "timePeriod": "1992–1993 outbreak context, with later ecological follow-up studies", "exposureContext": "Risk requires infected reservoir hosts and human contact with contaminated excreta; rainfall is an upstream ecological correlate, not a direct cause of infection." }, "references": [ { "referenceId": "hantavirus-climate-case-study-1999", "relation": "supports", "sourceRecordId": "PMID:10081675; PMCID:PMC2627709", "sourceVersion": "Published 1999; case and probable exposure-site analyses from 1993–1995" }, { "referenceId": "yates-hantavirus-2002", "relation": "supports", "sourceRecordId": "PMID:12473747", "sourceVersion": "Published 2002" }, { "referenceId": "openstax-hantavirus", "relation": "context", "sourceRecordId": "OpenStax Biology 2e: Hantavirus and El Niño", "sourceVersion": "Edition/version not recorded in this snapshot" } ] }, { "id": "hanta-risk-patterns-vary-across-sites", "version": 1, "subjectId": "taxon-deer-mouse", "predicate": "POPULATION_AND_INFECTION_RISK_VARY_WITH", "objectValue": "Site-level ecological conditions and their duration; 1999 crude Sin Nombre virus prevalence was higher at modeled high-risk than low-risk sites", "statement": "In a post-ENSO field study, deer-mouse captures increased at modeled high-risk sites, and crude Sin Nombre virus prevalence in 1999 was 30.8% at high-risk sites versus 8.3% at low-risk sites.", "qualifier": "These are site-level observations from a later study, not measurements of the 1993 Four Corners causal chain. The risk model and associations do not show that rainfall alone caused infection or human cases; ecology, sampling, and exposure remain distinct steps.", "evidenceKind": "primary_study", "context": { "scope": "Deer mouse–Sin Nombre virus–human system; ecological interpretation of the 1992–93 Four Corners outbreak", "organism": "North American deer mouse (Peromyscus maniculatus); human spillover is a separate host process", "taxonId": "10042", "conditionId": "disease-hantavirus-pulmonary-syndrome", "population": "Local rodent populations, infected-host prevalence, and human cases in the southwestern United States", "location": "Four Corners region / southwestern United States; evidence varies by study site", "timePeriod": "1992–1993 outbreak context, with later ecological follow-up studies", "exposureContext": "Risk requires infected reservoir hosts and human contact with contaminated excreta; rainfall is an upstream ecological correlate, not a direct cause of infection." }, "references": [ { "referenceId": "yates-hantavirus-2002", "relation": "supports", "sourceRecordId": "PMID:12473747", "sourceVersion": "Published 2002; post-ENSO field observations and modeled high-/low-risk sites" }, { "referenceId": "deer-mouse-rainfall-2018", "relation": "qualifies", "sourceRecordId": "PMID:29299286", "sourceVersion": "Published 2018; six Montana sites, lagged resource–abundance correlations at three" } ] }, { "id": "hanta-plant-productivity-link-is-site-dependent", "version": 1, "subjectId": "concept-epidemiology", "predicate": "ECOLOGICAL_RESOURCE_LINK_VARIES_BY_SITE", "objectValue": "Plant productivity and deer-mouse abundance were positively correlated with a lag at three of six studied Montana sites", "statement": "Later field work found that precipitation-linked plant productivity predicted deer-mouse abundance with a several-month lag at three of six study sites, with weaker effects when mouse populations were already larger.", "qualifier": "This study was conducted in central and western Montana, not the 1993 Four Corners outbreak; it demonstrates site dependence rather than directly explaining that outbreak.", "evidenceKind": "primary_study", "context": { "scope": "Deer mouse–Sin Nombre virus–human system; ecological interpretation of the 1992–93 Four Corners outbreak", "organism": "North American deer mouse (Peromyscus maniculatus); human spillover is a separate host process", "taxonId": "10042", "conditionId": "disease-hantavirus-pulmonary-syndrome", "population": "Local rodent populations, infected-host prevalence, and human cases in the southwestern United States", "location": "Four Corners region / southwestern United States; evidence varies by study site", "timePeriod": "1992–1993 outbreak context, with later ecological follow-up studies", "exposureContext": "Risk requires infected reservoir hosts and human contact with contaminated excreta; rainfall is an upstream ecological correlate, not a direct cause of infection." }, "references": [ { "referenceId": "deer-mouse-rainfall-2018", "relation": "qualifies", "sourceRecordId": "PMID:29299286", "sourceVersion": "Published 2018; six Montana sites" } ] }, { "id": "hanta-deer-mouse-reservoir", "version": 1, "subjectId": "taxon-deer-mouse", "predicate": "RESERVOIR_HOST_FOR", "objectId": "taxon-sin-nombre-virus", "statement": "North American deer mice are an important reservoir host for Sin Nombre virus in the United States.", "qualifier": "Reservoir status does not mean every deer mouse is infected; prevalence varies with place, time, host population, and sampling method.", "evidenceKind": "database_annotation", "context": { "scope": "Deer mouse–Sin Nombre virus–human system; ecological interpretation of the 1992–93 Four Corners outbreak", "organism": "North American deer mouse (Peromyscus maniculatus); human spillover is a separate host process", "taxonId": "10042", "conditionId": "disease-hantavirus-pulmonary-syndrome", "population": "Local rodent populations, infected-host prevalence, and human cases in the southwestern United States", "location": "Four Corners region / southwestern United States; evidence varies by study site", "timePeriod": "1992–1993 outbreak context, with later ecological follow-up studies", "exposureContext": "Risk requires infected reservoir hosts and human contact with contaminated excreta; rainfall is an upstream ecological correlate, not a direct cause of infection." }, "references": [ { "referenceId": "ncbi-deer-mouse", "relation": "context", "sourceRecordId": "NCBI Taxonomy:10042", "sourceVersion": "Record accessed 2026-09-27" }, { "referenceId": "cdc-hantavirus", "relation": "supports", "sourceRecordId": "CDC MMWR: Hantavirus Pulmonary Syndrome", "sourceVersion": "Page version not recorded in this snapshot" } ] }, { "id": "hanta-virus-can-spill-over-through-excreta", "version": 1, "subjectId": "taxon-sin-nombre-virus", "predicate": "CAN_EXPOSE_HUMANS_THROUGH", "objectId": "disease-hantavirus-pulmonary-syndrome", "statement": "People can acquire Sin Nombre virus after inhaling aerosolized material contaminated by infected deer-mouse urine, droppings, or saliva.", "qualifier": "This describes a recognized exposure route; infection requires exposure to infectious material, and human-to-human transmission is not the ordinary route for Sin Nombre virus.", "evidenceKind": "clinical_guideline", "context": { "scope": "Deer mouse–Sin Nombre virus–human system; ecological interpretation of the 1992–93 Four Corners outbreak", "organism": "North American deer mouse (Peromyscus maniculatus); human spillover is a separate host process", "taxonId": "10042", "conditionId": "disease-hantavirus-pulmonary-syndrome", "population": "Local rodent populations, infected-host prevalence, and human cases in the southwestern United States", "location": "Four Corners region / southwestern United States; evidence varies by study site", "timePeriod": "1992–1993 outbreak context, with later ecological follow-up studies", "exposureContext": "Risk requires infected reservoir hosts and human contact with contaminated excreta; rainfall is an upstream ecological correlate, not a direct cause of infection." }, "references": [ { "referenceId": "cdc-hantavirus", "relation": "supports", "sourceRecordId": "CDC MMWR: Hantavirus Pulmonary Syndrome", "sourceVersion": "Page version not recorded in this snapshot" }, { "referenceId": "hantavirus-mechanistic-2016", "relation": "supports", "sourceRecordId": "PMID:26955081", "sourceVersion": "Published 2016" } ] }, { "id": "hanta-human-risk-depends-on-contact", "version": 1, "subjectId": "disease-hantavirus-pulmonary-syndrome", "predicate": "RISK_DEPENDS_ON", "objectValue": "Rodent infection and shedding, host activity, peridomestic contact, human behavior, and environmental conditions", "statement": "Human disease risk depends on the encounter between infected reservoir hosts and people, including where rodents move and whether activities aerosolize contaminated material.", "qualifier": "Rodent abundance alone is not sufficient to predict human cases; housing, behavior, seasonal activity, viral prevalence, and case ascertainment also matter.", "evidenceKind": "mechanistic_review", "context": { "scope": "Deer mouse–Sin Nombre virus–human system; ecological interpretation of the 1992–93 Four Corners outbreak", "organism": "North American deer mouse (Peromyscus maniculatus); human spillover is a separate host process", "taxonId": "10042", "conditionId": "disease-hantavirus-pulmonary-syndrome", "population": "Local rodent populations, infected-host prevalence, and human cases in the southwestern United States", "location": "Four Corners region / southwestern United States; evidence varies by study site", "timePeriod": "1992–1993 outbreak context, with later ecological follow-up studies", "exposureContext": "Risk requires infected reservoir hosts and human contact with contaminated excreta; rainfall is an upstream ecological correlate, not a direct cause of infection." }, "references": [ { "referenceId": "hantavirus-mechanistic-2016", "relation": "supports", "sourceRecordId": "PMID:26955081", "sourceVersion": "Published 2016" } ] }, { "id": "hanta-causal-chain-has-unresolved-links", "version": 1, "subjectId": "concept-epidemiology", "predicate": "ECOLOGICAL_CAUSAL_CHAIN_REQUIRES", "objectValue": "Longitudinal evidence linking climate, resources, host abundance and infection, host movement, human exposure, and cases", "statement": "The proposed climate-to-human-disease chain contains links that remain incompletely measured, especially connections among reservoir behavior, virus transmission, and human exposure.", "qualifier": "This case is best used to compare a mechanistic hypothesis with field data, not as a deterministic rule that wet years produce outbreaks.", "evidenceKind": "mechanistic_review", "context": { "scope": "Deer mouse–Sin Nombre virus–human system; ecological interpretation of the 1992–93 Four Corners outbreak", "organism": "North American deer mouse (Peromyscus maniculatus); human spillover is a separate host process", "taxonId": "10042", "conditionId": "disease-hantavirus-pulmonary-syndrome", "population": "Local rodent populations, infected-host prevalence, and human cases in the southwestern United States", "location": "Four Corners region / southwestern United States; evidence varies by study site", "timePeriod": "1992–1993 outbreak context, with later ecological follow-up studies", "exposureContext": "Risk requires infected reservoir hosts and human contact with contaminated excreta; rainfall is an upstream ecological correlate, not a direct cause of infection." }, "references": [ { "referenceId": "hantavirus-mechanistic-2016", "relation": "supports", "sourceRecordId": "PMID:26955081", "sourceVersion": "Published 2016" }, { "referenceId": "deer-mouse-rainfall-2018", "relation": "qualifies", "sourceRecordId": "PMID:29299286", "sourceVersion": "Published 2018; site-dependent lagged associations" } ] } ], "limitation": "The climate-to-human-disease pathway is a proposed ecological chain, not a deterministic forecast. Studies differ in geography and methods, plant-resource effects vary by site, and unresolved links remain between host ecology, viral transmission, and actual human exposure." } } }