Getah Virus
LEVELS: Highly unlikely; No human illness; Extraordinary biosecurity required; Reference or research laboratory required; Moderate; Negligible; Substantial; Needed but not available
| Register id | getah_virus |
| Type | virus |
| Scientific name | Getah virus |
| NCBI taxid | 59300 |
| Evidence | 5 document(s) |
| Assigned | 2026-09-06, against criteria version 093366e352a2 |
Overview
Getah virus is a mosquito-borne alphavirus of Asia, present from Russia in the north to Malaysia in the south, and it is one of the few arboviruses on this register that genuinely damages pigs. It circulates in a mosquito-vertebrate-mosquito cycle with horses and pigs as the main amplifying hosts, and has since been found in foxes, cattle and other species; it has also been recovered from biting midges, from wastewater treatment plants, and as a contaminant of veterinary vaccines. In horses the illness is usually mild and self-limiting, but in pigs it causes reproductive disorders in sows and death in piglets — the 1987 index outbreak involved newborn piglets with 100% case mortality. A more pathogenic strain emerged in Japan in 2014 and spread to China, causing repeated outbreaks in horses, pigs and farmed blue foxes over an expanding area. Diagnosis is by virus isolation or RT-PCR, with serology complicated by cross- reaction with Ross River and chikungunya viruses and by the absence of any test that can distinguish vaccinated from infected animals. An inactivated vaccine is used successfully in Japanese racehorses; there is none for pigs. Antibodies have been found in people but no illness has ever been associated with the virus, and current strains are not thought to be zoonotic.
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
CONFIRMED by Eric. The assignment reached this level from the evidence, and he has reviewed and ratified it.
Confirmed by Eric. CONFIRMED. "c1l1, i have uploaded 2 papers into inbox for you to review against all Getah criteria. There is some contradiction around C1 but there seems to be zero evidence of clinical disease or human-human transmission. We will downgrade it unless your review turns up something else."
Basis. Yuen 2024: "Laboratory studies demonstrated that human-derived cell lines were resistant to GETV infection (Zhang et al., 2021)." "Based on existing data, it is reasonable to suggest that currently circulating GETV strains are not likely a zoonotic pathogen and the detection of GETV antibodies in early studies may potentially be due to non-specific or cross-reactivity to antigenically related viruses." Li 2026: "as of 2025, no confirmed clinical cases or viral isolates from human samples have been reported, and the possibility of serological cross-reactivity with other alphaviruses cannot be ruled out." "GETV remains primarily an animal pathogen... rather than an established human pathogen." 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
MOVED L2 -> L1, and the two reviews Eric supplied settle the contradiction that produced the L2. ch41 41.6.1 asserted "GETV is zoonotic in humans" on a single 2022 citation and said nothing more; the CFSPH factsheet already in the folder reported human antibodies with no associated illness. These resolve it in the direction he predicted, and on a mechanism rather than an absence: human cell lines are RESISTANT to the virus. That removes the basis for the L2 I scored -- pigs may be viraemic and share vectors with people, but a virus that cannot enter human cells is not reaching humans from pigs. The antibody detections that made it look zoonotic are attributed by both reviews to cross-reactivity with related alphaviruses, which is the same artefact Eric identified on chikungunya. NOTE: Yuen adds that "the potential for zoonotic GETV strains to arise due to virus mutations should not be discounted", and the general rule forbids scoring hypothetical future variants. 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, There is some contradiction around C2 but there seems to be zero evidence of clinical disease or human-human transmission. We will downgrade it unless your review turns up something else."
Basis. Li 2026: "although no confirmed clinical cases in humans have been reported to date, serological evidence from healthy individuals and febrile patients... suggests possible subclinical or past infections", and "as of 2025, no confirmed clinical cases or viral isolates from human samples have been reported". Yuen 2024 reaches the same place. CFSPH 2017: "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
MOVED L2 -> L1. C2 says to score level 1 whenever the agent does not cause disease in people, and three independent documents now say no human clinical case has ever been confirmed. The L2 I scored was a split between two documents that disagreed; they no longer disagree. NOTE, recorded because Li states it against its own conclusion: "the scarcity of human detections may partly reflect diagnostic neglect: febrile illnesses are rarely screened specifically for GETV, and serological cross-reactivity with other endemic alphaviruses (e.g., Ross River virus and CHIKV) complicates data interpretation." Level 1 records the state of the evidence, not a proof that human disease cannot occur. 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. Li 2026: "the reservoir range of GETV is broad, ranging from primary vectors (e.g., mosquitoes) and key amplifying hosts (e.g., horses and pigs) to a variety of newly identified hosts such as foxes, cattle, red pandas". "Its transmission is maintained through an enzootic mosquito-vertebrate-mosquito cycle." GETV was also "isolated from midges in Yunnan (2013) and Xinjiang (2016)", and detected "in wastewater treatment plants" and as a contaminant of veterinary vaccines. 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. Level 4 unchanged and substantially better evidenced. The reservoir is not merely mosquitoes and pigs but an enzootic cycle spanning horses, foxes, cattle and wildlife, with midges as a second arthropod vector. Two routes appear that the chapter does not mention: environmental detection in wastewater, and iatrogenic transmission through contaminated veterinary vaccines. None is closed by farm biosecurity. Level 4 confirmed, and the factsheet names the level 4 measure itself -- SCREENED buildings, which is the insect-exclusion end of the filtration list. Housing alone is not offered as sufficient, and under the standing rule housing does nothing when the route is something that flies.
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: diagnosis "by viral isolation in rabbit kidney (RK-13) or Vero cells, or by detection of viral RNA by real-time RT-PCR. ELISA or hemagglutination-inhibition is available for use in paired sera." Yuen 2024 adds a specific limitation: "As a DIVA (differentiating infected and vaccinated animals) assay is currently not available for GETV, detection of antibodies should be interpreted with consideration of GETV vaccination history." Li 2026 notes serological cross-reactivity with Ross River virus and chikungunya "complicates data interpretation". 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
Level 3 unchanged, with two reasons added. Validated assays exist, so this is not level 4 -- but no DIVA assay exists, so serology cannot separate infection from vaccination where equine vaccine has been used, and cross-reactivity with other alphaviruses confounds it further. For an exotic arbovirus in US swine, confirmation goes to a reference laboratory. 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." "While infections in horses are often mild and self-limiting, 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." ch41 41.6.2.2 records the 1987 index outbreak in newborn piglets with 100% case mortality. 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
Level 3 unchanged, now supported by two reviews rather than by the chapter alone, and the picture is worse rather than better: a highly pathogenic strain emerged in 2014 and is expanding geographically, causing outbreaks in pigs with reproductive disorders in sows and piglet mortality. Measurable and episodic rather than a standing burden, which holds it at level 3 rather than 4. 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 not expect any market impact from Getah diagnosis"
Basis. Neither document records a trade measure, movement control, export restriction or consumer response for GETV. It is not WOAH-listed. The disease is confined to Asia and has never occurred in the Americas. 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, and the standing note SCORING/market_impact does not settle this one: it is scoped to agents already endemic or already diagnosed in US pigs, and GETV is neither, so there is no absence of reaction to reason from. Scored on what would happen. A non-notifiable arbovirus causing sporadic piglet mortality would be a herd-level animal health event rather than a trade one -- there is no listing to trigger a restriction and no food safety dimension. Level 1. FLAGGED as reasoned rather than observed: a novel arbovirus establishing in US swine would attract attention the chapter gives no basis to quantify. 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
CONFIRMED by Eric. The assignment reached this level from the evidence, and he has reviewed and ratified it.
Confirmed by Eric. CONFIRMED. "c7l3, some evidence of severe disease in pigs and treatment may be useful if it were available"
Basis. No treatment for GETV in pigs is described in ch41 41.6.5, which addresses the virus only through the equine vaccine and vector control. The losses in 41.6.2.2 and 41.6.3.2 are 100% case mortality in newborn piglets, fetal death, and depressed growth. 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
INFERRED. No pathogen-directed treatment exists, and unlike the other three alphaviruses here there is a real outcome for one to improve -- newborn piglet mortality and reproductive loss. Both halves of level 3. NOTE: an antiviral would have to reach neonates within a very short window to change the 100% case mortality figure, which is an argument that the achievable benefit is smaller than the raw mortality suggests. 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
Level 3 unchanged. No GETV vaccine exists in the United States for any species, and 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. 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 for this virus 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/getah_virus.yml; the overview is authored in data/overviews/getah_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.