Sagiyama Virus
LEVELS: Highly unlikely; No human illness; Extraordinary biosecurity required; Reference or research laboratory required; Moderate; Negligible; Substantial; Needed but not available
| Register id | sagiyama_virus |
| Type | virus |
| Scientific name | Sagiyama virus |
| NCBI taxid | 59303 |
| Evidence | 5 document(s) |
| Assigned | 2026-09-06, against criteria version 093366e352a2 |
Overview
Sagiyama virus is a close variant of Getah virus, separated from it historically by a single amino acid difference in the capsid protein and by complement fixation testing. It is mosquito- borne, with Culex tritaeniorhynchus and Aedes vexans as the main vectors, and natural subclinical infection of pigs was first reported in the 1960s: 67% of pigs in one survey carried neutralising antibody, against 18% of the people living nearby. It appears to be essentially non-pathogenic to pigs. The one outbreak attributed to it involved pigs simultaneously infected with Japanese encephalitis virus and PCV2, and inoculating pigs with Sagiyama virus alone produced no disease. Because viraemia is brief, isolating the virus has little diagnostic value and the practical approach is serology, where a high antibody titre or a seropositive rate above 50% indicates repeated exposure. No human illness has been associated with it or with Getah virus. There is no vaccine for pigs, and on present evidence none is needed.
C1 Zoonotic potential
Likelihood of transmission from pigs to humans
Highly unlikely: Human infection with the agent has never been reported, or has been reported but is not attributed to pig or pork exposure
Basis. ch41 41.6.2.3: "Natural subclinical infection in pigs was first reported in the 1960s, and the virus neutralization (VN) antibody rate in pigs was 67% vs. 18% in humans living in the vicinity of infected pigs." SAGV "is considered a variant of GETV" and is mosquito-borne, with Culex tritaeniorhynchus and Aedes vexans the major vectors. shic_getah: "Antibodies to GETV have been identified in humans, and strain M-1 was implicated as a possible cause of febrile disease. However, there are no reports of clinical disease in people."
How this level was decided
Level 1 on Eric's standing note. The 67%-versus-18% figures are the shape his chikungunya reasoning describes: pigs and people in the same place being bitten by the same mosquitoes, which produces antibodies on both sides without making the pig the source for the person. Eric's standing note at chikungunya_virus/zoonotic_potential names this virus specifically: "Same dead-end reasoning applies to Ross River, Sagiyama, dengue, Zika, eastern equine encephalitis and Murray Valley." The framework scores pig-to-human only, and a pig that does not seed a mosquito is not a source however much virus is in the neighbourhood. Level 1 confirmed. The factsheet reproduces exactly the pattern Eric settled on for this entry and for chikungunya: human antibodies without human illness, which the reviews in this folder attribute to cross-reactivity among alphaviruses.
C2 Zoonotic impact
Severity of human illness caused by the agent
No human illness: Agent does not cause illness in people
CONFIRMED by Eric. The assignment reached this level from the evidence, and he has reviewed and ratified it.
Confirmed by Eric. CONFIRMED. "c2l1, we should make all criteria ratings the same for both Getah and Sagiyama, review all and update. This will allow the two to float in parallel in the overall ranking, but still facilitate new evidence if or when it arrives"
Basis. ch41 41.6 describes no human illness caused by SAGV, though 18% of people living near infected pigs carried neutralising antibody. The CFSPH factsheet placed on getah_virus, which treats SAGV as a strain of Getah virus, states: "Although antibodies to Getah virus have been found in humans, there are no reports of any illnesses associated with this virus." shic_getah: "there are no reports of clinical disease in people."
How this level was decided
INFERRED. Human infection demonstrably occurs -- 18% seropositivity near infected herds -- but no illness has ever been reported from it, which the CFSPH factsheet states in terms for the virus SAGV is a strain of. C2 says to score level 1 whenever the agent does not cause disease in people. Level 1. NOTE: seropositivity without reported illness is a weaker basis than an examined negative, so this is a fair cell to challenge. Level 1 confirmed.
C3 Herd introduction risk
Effort required to keep the agent out of the herd
Extraordinary biosecurity required: Exclusion needs measures beyond the routine, such as air filtration, thermally treated feed and bedding, or repeated costly testing to find carriers, and may still fail
Basis. ch41 41.6.2.3: "Culex tritaeniorhynchus and Aedes vexans are believed to be the major vectors." SAGV is a mosquito-borne alphavirus, a variant of GETV, which is "present throughout Asia, as far north as Russia and as far south as Sarawak in Malaysia". shic_getah: "GETV is maintained in a transmission cycle between mosquitoes and vertebrate hosts. Both horses and pigs are amplifiers. The main vectors are Culex tritaeniorhynchus, Aedes vexans nipponii, Cx. gelidus, and Cx. fuscocephala." "GETV prevention in endemic areas centers on mosquito control (i.e., remove standing water where mosquitoes lay eggs, use insecticides to kill both mosquito larvae and adults, house animals indoors/in screened buildings, etc.)."
How this level was decided
RENUMBERED L5 -> L4 on 2026-09-03, when C3 was reduced from five levels to four and level 4 absorbed level 5. THE JUDGMENT IS UNCHANGED and this one really is a renumber: the merged level 4 label carries what level 5 said, ending "and may still fail". IT WAS STILL CHECKED rather than assumed, because the last renumber on 2026-09-01 was mechanical and moved twenty-one entries past a level they should have been judged against. The check is the exclusion test -- does housing close the route? For this entry it does not.
EARLIER REASONING, kept because it is the evidence read: RENUMBERED L4 -> L5 on 2026-09-01, when C3 went from four levels to five. The argument below is unchanged and so is the judgment. What changed is the scale it sits on. C3 now runs on the EFFORT REQUIRED TO EXCLUDE: L1 already in the herd, L2 housing alone keeps it out, L3 routine biosecurity keeps it out, L4 extraordinary biosecurity required, L5 exclusion may not be achievable. Mosquito-borne with no reliance on the pig industry to maintain it -- arthropod vectors are named in the level 4 definition, and Eric's JEV note establishes that competent Culex species are present in the US "even if they are not ideal vectors". Level 4. Level 4 confirmed on the same mosquito-borne reasoning as getah_virus. The factsheet places Sagiyama in the same serocomplex -- GETV "is an Old World alphavirus belonging to the Semliki Forest serocomplex, which includes closely-related Sagiyama virus" -- and the vector biology is shared.
C4 Detection difficulty
Difficulty of recognizing and confirming infection
Reference or research laboratory required: A validated assay exists, but only at a national reference or research laboratory rather than at local or regional level
Basis. ch41 41.6.4: "SAGV isolation is definitive but has little diagnostic value due to the transient nature of viremia. Antibody detection is indicative of SAGV infection, with VN antibody titers >1:48 or a seropositive rate >50% suggestive of repeated exposures to SAGV." 41.6.2.3: SAGV is differentiated from GETV "by complement fixation due to the presence of the amino acid leucine in the SAGV capsid protein". shic_getah: "Several reverse transcriptase polymerase chain reaction (RT-PCR) assays have been developed for GETV. Targets include nonstructural proteins 1, 2, and 3." "Antibodies can be detected via enzyme-linked immunosorbent assay (ELISA), serum neutralization (SN), hemagglutination inhibition (HI), and complement fixation (CF)."
How this level was decided
Nothing prompts a test, since the chapter calls SAGV nonpathogenic to pigs. Isolation is described as having little diagnostic value, and telling SAGV from GETV needs complement fixation resolving a single amino acid difference in the capsid -- reference or research work by any reading. Level 3. Level 3 confirmed. Assays exist in quantity, so not level 4; but for an agent absent from North America nothing would be run outside a reference or research laboratory.
C5 Production cost
Financial impact on the infected farm's cost of production
Moderate: Losses measurably increase cost of production but remain manageable within normal farm operations, whether acute, chronic, or associated with endemic disease
Basis. Yuen 2024: "A highly pathogenic strain of GETV emerged in 2014 in Japan and spread to China causing multiple outbreaks in horses, pigs, and blue foxes with an expanding geographical distribution." "infected blue foxes, pregnant sows and piglets can present with reproductive and neurological signs." Li 2026: "GETV infection can cause fever and edema in horses, reproductive disorders in sows, and piglet mortality." Against that, ch41 on SAGV specifically: the one outbreak attributed to Sagiyama virus involved concurrent JEV and PCV2 infection, and inoculation of SAGV alone produced no disease. shic_getah: "Most GETV infections are subclinical in adult pigs." "Piglets may develop anorexia, depression, diarrhea, and neurological signs, with death occurring in several days." "Fetal death occurs in pregnant sows, especially if viral exposure occurs before 28 days of gestation." "Seroprevalence studies show that GETV is common in swine in Asia (up to 100% following outbreaks)... Mortality in swine can be high, particularly in neonates." "GETV outbreaks in swine have occurred since 2017 in China."
How this level was decided
MOVED L1 -> L3 on 2026-09-02. The two readings in the folder now disagree, and that disagreement IS the identity question. Read as a separate agent, Sagiyama virus is nonpathogenic and the chapter shows the working -- the single attributed outbreak had JEV and PCV2 in it and pure SAGV inoculation produced nothing, which is a confounder identified and removed. Read as a strain of Getah virus, which is what the CFSPH factsheet now in this folder says it is, the agent has a highly pathogenic 2014 lineage causing sow reproductive disorders and piglet mortality across an expanding range. Scored identically to getah_virus on Eric's ruling of 2026-09-02: "we will leave sagiyama and getah as independent entries but just ensure both have identical ratings for each criteria... We will kill one off later if necessary but i want to retain visibility of both." The three Getah documents were copied into this folder the same day, so the two entries now rest on the same evidence and reach the same level. NOTE FOR THE RECORD: this is the cell where the alignment costs something. The Sagiyama-specific evidence is an examined negative and it is being overridden by the Getah literature on the strength of a taxonomic opinion. Level 3 confirmed and better evidenced than before: neonatal mortality plus reproductive loss, against a background of subclinical infection in adults. Measurable and manageable rather than unsustainable.
C6 Market impact
Duration of material disruption to pork and pig markets
Negligible: Little or no material disruption to supply or demand when disease occurs on one or more farms
CONFIRMED by Eric. The assignment reached this level from the evidence, and he has reviewed and ratified it.
Confirmed by Eric. CONFIRMED. "c6l1, we should make all criteria ratings the same for both Getah and Sagiyama, review all and update. This will allow the two to float in parallel in the overall ranking, but still facilitate new evidence if or when it arrives"
Basis. Section 41.6 records no trade measure, movement control or consumer response for SAGV, which is described as nonpathogenic to pigs. shic_getah: "GETV is not an OIE-listed disease. There are no recommendations for importation of horses or swine from countries or zones affected by GETV."
How this level was decided
INFERRED. A nonpathogenic mosquito-borne virus has no route to pork supply or demand. Level 1. Level 1 confirmed, and the cell moves to a direct statement: no listing, no import recommendation, despite repeated swine outbreaks in China since 2017.
C7 Treatment potential
Potential for treatment to improve outcomes
Substantial: No effective treatment (antimicrobial, antiviral, antiparasitic, herbal or other) is available, but outcomes would meaningfully improve if one existed
Basis. No treatment for GETV or SAGV in pigs is described in ch41 41.6.5, which addresses the virus only through the equine vaccine and vector control. The outcome a treatment would act on is in 41.6.2.2 and 41.6.3.2: 100% case mortality in newborn piglets, fetal death and depressed growth. Yuen 2024 and Li 2026 add sow reproductive disorders and piglet mortality from the post-2014 lineage. shic_getah: "There are no alphavirus-specific antiviral drugs." "Even in humans, the pathogenesis of alphavirus infection is not clearly understood, and licensed vaccines and targeted anti-viral therapies are lacking."
How this level was decided
MOVED L1 -> L3 on 2026-09-02. No pathogen-directed treatment exists anywhere, and once the entry is read as Getah there is a real outcome for one to improve -- newborn piglet mortality and reproductive loss. Both halves of level 3. Scored identically to getah_virus on Eric's ruling of 2026-09-02: "we will leave sagiyama and getah as independent entries but just ensure both have identical ratings for each criteria... We will kill one off later if necessary but i want to retain visibility of both." The three Getah documents were copied into this folder the same day, so the two entries now rest on the same evidence and reach the same level. NOTE: an antiviral would have to reach neonates within a very short window to change the outcome, which is the same caveat recorded on getah_virus. Level 3 held, on Eric's own confirmation of this cell -- "c7l3, some evidence of severe disease in pigs and treatment may be useful if it were available". NOTE A DEFECT IN THE STANDING NOTE, not in this cell: SCORING/treatment_potential lists getah_virus among the entries scored at level 1 because the harm is transplacental and complete before birth. That is out of date -- his ruling puts it at 3, and the factsheet supports him, because the neonatal deaths are in piglets born healthy and dying days later, which is a window a treatment could act in. The note should be corrected so a future pass is not misled.
C8 Vaccine availability
Availability of effective vaccines or bacterins
Needed but not available: No effective vaccine is available in the US or has been developed, and the disease would justify vaccinating if one existed
Basis. ch41 41.6.5: "For GETV, an inactivated vaccine has been used successfully in racehorses." CFSPH 2017: Japanese racehorses receive two doses of inactivated vaccine with an annual booster, and "no cases were reported there between 1984 and 2014". Yuen 2024 records that no DIVA assay exists for GETV. Li 2026 reports GETV contamination of veterinary vaccines. shic_getah: "A live-attenuated trivalent vaccine (GETV, JEV, and porcine parvovirus) has been available for swine in Japan since 1993; however, its efficacy is unknown since currently circulating GETVs are different from vaccine strains."
How this level was decided
MOVED L1 -> L3 on 2026-09-02. No vaccine exists in the United States for any species, and read as Getah the disease would warrant one on piglet mortality and sow reproductive loss. The target is demonstrably tractable: an inactivated equine vaccine held Getah out of Japanese racehorses for thirty years. Scored identically to getah_virus on Eric's ruling of 2026-09-02: "we will leave sagiyama and getah as independent entries but just ensure both have identical ratings for each criteria... We will kill one off later if necessary but i want to retain visibility of both." The three Getah documents were copied into this folder the same day, so the two entries now rest on the same evidence and reach the same level. NOTE, and it is a caution rather than a change: Li reports GETV contaminating veterinary vaccines, so a vaccination programme is itself a documented transmission route if the product is not clean. Level 3 confirmed. The Japanese trivalent product proves the target is tractable while leaving the US gap open, and the factsheet adds that even that vaccine may no longer match circulating strains.
Levels and evidence are generated from data/assignments/sagiyama_virus.yml; the overview is authored in data/overviews/sagiyama_virus.md. Do not hand-edit this page — corrections go in data/assignments/CORRECTIONS.yml.
Quoted material marked Basis is from Zimmerman JJ, Karriker LA, Ramirez A, Schwartz KJ, Stevenson GW, Zhang J, eds. Diseases of Swine, 12th edition. Hoboken: Wiley Blackwell, 2025 — except where another source is named in the quotation itself.