Swine Acute Diarrhea Syndrome Coronavirus
LEVELS: Highly unlikely; No human illness; Extraordinary biosecurity required; Laboratory-dependent; Moderate; Significant disruption; Substantial; Needed but not available
| Register id | sads_cov |
| Type | virus |
| Scientific name | Swine acute diarrhea syndrome coronavirus |
| NCBI taxid | 2032731 |
| Evidence | 2 document(s) |
| Assigned | 2026-09-04, against criteria version 093366e352a2 |
Overview
Swine acute diarrhea syndrome coronavirus emerged in Guangdong province, China, in 2017, killing about 25,000 piglets in its first outbreak. It came from bats: the virus is 94.9% identical to a bat coronavirus and up to 98.48% identical to one found in bats near the index farms, and the different lineages seen since appear to represent separate spillover events. It causes watery diarrhoea and vomiting indistinguishable from PED, TGE or deltacoronavirus infection, and can kill up to 90% of piglets five days old or younger, though mortality falls to around 5% in pigs over eight days. Experimental results have been inconsistent — one study saw 100% mortality, another only mild signs — so its true severity is still being worked out. It has been reported only from Guangdong, Fujian and Guangxi provinces, with further outbreaks in 2019 and 2021, and testing of more than 1,800 US clinical samples between 2019 and 2021 found none. There is no vaccine and no approved treatment. Two features keep it on watch lists: its broad ability to grow in cells from many species including humans — though there is no epidemiological or serological evidence it has ever infected a person — and the fact that feeding infected intestinal material back to sows, a common control tactic for PED, is strongly discouraged here because of the risk of amplifying an uncharacterised bat-origin virus.
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. REVIEWED ON C1_C2_RECLASSIFICATION.md, 2026-09-04, after the C1/C2 rewording that separated exposure from consequence. Eric marked up every moved cell and reversed his own earlier setting on twenty of the twenty-one: "In almost every case, I agreed with new opinion and reversed my old setting." HIS MARKUP HERE WAS "l1, no evidence to support SADS is zoonotic". Reverses his 2026-09-02 level 2, with his reason: "no evidence to support SADS is zoonotic". ch28 28.6.3 and puente_2026 agree -- never identified in a human by any method.
Basis. ch28 28.6.3, the whole public health section: "Although research suggested that SADS-CoV could infect cell lines or primary cells from humans, there is no epidemiological or serological evidence of SADS-CoV infection of humans." 28.6.1: the virus originated from bats, sharing 94.9% homology with a bat coronavirus and up to 98.48% identity with a HKU2-like coronavirus found in bats near the index farms, and "Growing evidence has shown that SADS-CoV has broad host tropism (e.g. chickens and mice), i.e. possesses the potential for cross-species transmission". 28.6.2: "SADS-CoV is infectious for cells from swine, human, bat, monkey, dog, cat, mouse, and other species." SECOND SOURCE, puente_2026, which puts SADS-CoV with PDCoV as possessing "the highest empirical and theoretical zoonotic potential" of the group while confirming the negative: "while SADS-CoV has not yet been identified in human patients, its direct evolutionary lineage from bat CoVs (HKU2), its proven ability to experimentally infect diverse animal models, including rodents and avian species, its high efficiency in replicating within human respiratory and intestinal cell lines in vitro, and its proven ability to establish subclinical infections in murine models signal a potential zoonotic threat that demands rigorous public health surveillance." On entry: the virus "does not appear to utilise several well-known CoV receptors such as APN, angiotensin-converting enzyme 2 (ACE2), or dipeptidyl peptidase 4 (DPP4), suggesting that viral entry may rely on a more conserved host factor that could contribute to its broad cell tropism and cross-species infectivity."
How this level was decided
MOVED L2 -> L1, re-read 2026-09-04 AGAINST THE REWORDED LABELS. ch28 28.6.3: "there is no epidemiological or serological evidence of SADS-CoV infection of humans", and puente_2026 agrees -- "SADS-CoV has not yet been identified in human patients". Never reported in a person by any method, so level 1 on the first clause.
PREVIOUS ANSWER, kept because the evidence behind it has not changed, only the level boundary: Level 2. Human cells are susceptible in vitro, which is more than nothing -- and it is the opposite of the finding that put getah_virus at level 1, where human cell lines were RESISTANT. Add a bat origin, demonstrated infection of mice and chickens, and a virus that has already crossed species at least three separate times into pigs. But no human infection has ever been detected by any method, and nothing in pork production addresses it. Plausible, never reported, no control point: level 2. FLAGGED as a level 1 or 2 judgment -- cell-line susceptibility is a laboratory result and Eric has previously discounted such findings where in vivo evidence was absent. Corroborated and strengthened 2026-09-04. Eric confirmed level 2 on 2026-09-02 -- "c1l2, agree with assessment based on findings that zoonotic transmission is plausible and in line with the level description" -- and puente_2026 sharpens the plausibility without moving the fact that no human infection has ever been detected. THE NEW ELEMENT IS THE RECEPTOR ARGUMENT: SADS-CoV uses none of the three receptors that limit the tropism of the other porcine coronaviruses, which is why the review treats its host range as open rather than merely broad. The pass's original flag -- that cell-line susceptibility is a laboratory result -- is weakened by this, because the mechanism is now the point rather than the cell line.
C2 Zoonotic impact
Severity of human illness caused by the agent
No human illness: Agent does not cause illness in people
Basis. ch28 28.6.3: "there is no epidemiological or serological evidence of SADS-CoV infection of humans." No human illness of any kind attributable to SADS-CoV is described.
How this level was decided
Level 1. Under C2 as rescoped on 2026-09-01, the criterion grades illness acquired from pigs, and no human illness with this agent has ever been observed from any source. THE LABEL MUST NOT BE READ AS A FINDING THAT THIS VIRUS IS HARMLESS TO PEOPLE -- it records that nobody has been made ill by it, in a virus whose family has a conspicuous record of proving that kind of statement temporary.
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
CONFIRMED by Eric. The assignment reached this level from the evidence, and he has reviewed and ratified it.
Confirmed by Eric. CONFIRMED. "c3l4, many farms that thought they had great biosecurity became infected with PED during the first incursion, and we would expect no different if SADS-CoV turned up in the US. Virus is hardy in the environment, shed in high concentrations, and has a low infectious dose - logical it would be set at c3l4"
Basis. ch28 28.6.1: SADS-CoV originated from bats, with "up to 98.48% identity to a HKU2-like coronavirus detected in 2016 in bats near the index pig farms", and "different lineages of SADS-CoVs represented different spillover events from bats to pigs". 28.6.4: "To date, SADS-CoV has been detected only in Guangdong, Fujian, and Guangxi provinces in China and has not been reported outside of China. In a recent study, over 1800 clinical swine samples from various US states (2019-2021) were tested by PCR and none was positive for SADS-CoV." 28.6.10: "prevention and control measures described for TGEV and PEDV infections also apply to SADS-CoV." SECOND SOURCE, puente_2026, WHICH EXTENDS THE RANGE ch28 RECORDED: beyond Guangdong, Fujian and Guangxi, there is now "documented re-emergence in Guangxi province in 2021 and subsequent detection in inland regions such as Henan province in 2023 and confirmed positive cases in Jiangxi province", plus "retrospective analysis of porcine faecal samples from Vietnam has detected SADS-CoV by RT-qPCR in 5 out of 69 tested samples" -- "the first and only report of this virus outside China to date". The review reads the apparent confinement as partly artefact: geographic restriction "should not be automatically interpreted as an intrinsically lower dissemination capacity" but reflects "lower surveillance intensity, limited availability and implementation of routine differential diagnostics, varying reporting practices, and restricted sampling", illustrating "the threat of silent, undetected transboundary movement".
How this level was decided
INFERRED, and level 5 is deliberately NOT scored here -- this is the bat rule, and it is the reason the flag matters. The reservoir is Chinese horseshoe bats, which do not occur in North America, so an incursion would arrive without its ecosystem and the onward source would be other pig herds. That is Eric's Hendra ruling: an agent arriving here brings itself, not its reservoir. What remains is an enteric coronavirus transmitted by the faecal-oral and fomite routes, and the chapter says its prevention is the same as for PEDV -- which is scored level 4 because those routes have twice defeated routine biosecurity at national scale in the US, with PEDV in 2013 and PDCoV in 2014. Level 4. FLAGGED: no US bat has been shown to carry a HKU2-like coronavirus, and if one were, this would be level 5. Corroborated and strengthened 2026-09-04. Eric confirmed level 4 on 2026-09-02 on the PED precedent -- "many farms that thought they had great biosecurity became infected with PED during the first incursion, and we would expect no different if SADS-CoV turned up in the US" -- and the new source supports it from a different direction: the virus has already moved out of its original provinces and out of China undetected, which is the transboundary step the level 4 argument assumes. The bat rule that keeps this off the old level 5 is unaffected; puente_2026 confirms the reservoir is Rhinolophus bats.
C4 Detection difficulty
Difficulty of recognizing and confirming infection
Laboratory-dependent: The presentation does not point to this disease specifically, but local or regional laboratories can confirm it with a validated assay once it is suspected
Basis. ch28 28.6.6: "Clinical signs of SADS-CoV-infected piglets are similar to those caused by other swine enteric CoVs, including PEDV, TGEV, and PDCoV." 28.6.8: "Several real-time RT-PCR assays have been described; reverse-transcription LAMP and RPA assays have also been reported. Many methods for simultaneously detecting multiple swine enteric CoVs (SADS-CoV, PEDV, TGEV and PDCoV) have been described, e.g. TaqMan multiplex real-time RT-PCR, microfluidic-RT-LAMP chip for point-of-care detection, dual priming oligonucleotide system-based multiplex RT-PCR assay, and CRISPR-Cas12a combined with multiplex RT-LAMP assay." "Several studies have demonstrated no serological cross-reaction between SADS-CoV and other known swine CoVs." 28.6.4: "over 1800 clinical swine samples from various US states (2019-2021) were tested by PCR and none was positive for SADS-CoV."
How this level was decided
Level 2, AND THIS IS UNUSUAL FOR AN EXOTIC AGENT -- most score level 3 because the assay lives in a reference laboratory abroad. Not this one. US laboratories have already run SADS-CoV PCR on more than 1800 clinical swine samples across multiple states, which means the assay is validated, deployed and in routine surveillance use here before the virus has ever arrived. The clinical picture points nowhere, being identical to PEDV, TGEV and PDCoV diarrhoea, but the multiplex panel that separates them is standard regional work and serology shows no cross-reaction with the other swine coronaviruses.
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
CONFIRMED by Eric. The assignment reached this level from the evidence, and he has reviewed and ratified it.
Confirmed by Eric. CONFIRMED. "c5l3, agree with assessment. Field evidence and actions of related virus all indicate this would be a consequential pathogen in the US"
Basis. ch28 28.6.1: the 2017 Guangdong outbreak "resulted in approximately 25,000 piglet deaths". 28.6.4: the 2019 re-emergence caused "approximately 2000 piglet mortalities" on one farm, and in May 2021 a new variant "caused an outbreak with more than 3000 piglet deaths in a pig farm in Guangxi province". 28.6.6: "In sucking piglets less than or equal to 5 days of age, mortality from SADS-CoV infection can be up to 90%, whereas in piglets >8 days of age, the mortality was 5%." Against that, 28.6.5 records contradictory experimental results, from 100% mortality in one study to "no or mild-to-moderate clinical signs" in another, and the chapter concludes that "the variable outcomes among SADS-CoV pig studies justifies the need for further research". SECOND SOURCE, puente_2026: the 2017 outbreak caused "~24,500 piglet deaths and substantial economic losses"; "In piglets under 5 days of age, clinical disease progresses rapidly, leading to severe dehydration and death within 2-6 days post-infection"; and prevalence in a 2021-2023 southern China survey was "5.16% (11/213) of investigated pig farms". A nationwide survey of 12,978 sera reported 59.97% seropositivity, WHICH THE AUTHORS THEMSELVES CAUTION AGAINST: "there is potential for serological cross-reactivity with an as-yet-unidentified pathogen. Therefore, this high seroprevalence highlights the urgent need for highly specific differential diagnostics rather than definitively confirming widespread SADS-CoV infection."
How this level was decided
Level 3, scored on what an incursion would cost. The field record is consistent and expensive -- three separate Chinese outbreaks killing 25,000, 2,000 and 3,000 piglets, with up to 90% mortality in the first five days of life -- but the age window is narrow, mortality falls to 5% by eight days, and the events were farm-level rather than industry-level. Losses that measurably increase cost of production and are managed within normal operations, the same reading as the other enteric coronaviruses in this chapter. FLAGGED: the experimental pathogenicity data are frankly contradictory, ranging from 100% mortality to no clinical signs, so the severity of a US incursion is less predictable than the field numbers suggest. Corroborated 2026-09-04. Eric confirmed level 3 on 2026-09-02: "field evidence and actions of related virus all indicate this would be a consequential pathogen in the US". THE 59.97% SEROPREVALENCE FIGURE MUST NEVER BE QUOTED WITHOUT THE AUTHORS' OWN CAVEAT -- read alone it says most Chinese pigs have met this virus, which would change the picture entirely, and the authors say it may be cross-reactivity with something unidentified. The farm-level prevalence that is not in doubt is 5.16%. The contradictory experimental pathogenicity flagged in the original assessment is unresolved by the new source.
C6 Market impact
Duration of material disruption to pork and pig markets
Significant disruption: Material negative effect on supply or demand lasting 1 to 6 months when disease occurs on one or more farms
INFERRED — reasoned, not stated. The evidence implies this level rather than stating it. The reasoning is below.
Corrected by Eric from L1 Negligible. Reason: MOVED L1 -> L3. On the gaps sheet he wrote "c6l1, i have upgraded this because if it behaves true to form with PED for an example, an incursion would be expected to spread widely and quickly, and kill many young pigs. This had a direct market impact with PED 2013/14 and I would expect the same with SADs." THE STATED LEVEL AND THE STATED REASONING DISAGREED -- he wrote level 1, which means negligible, while describing an upgrade and a direct market impact -- so the cell was held rather than written, under his own instruction of 2026-09-02 to ask when a ruling is not clear. Asked, he chose LEVEL 3: a material effect on supply or demand lasting one to six months. THE DISTINCTION FROM HIS OWN PEDV RULING IS THE POINT, and it is not an inconsistency. He scored porcine_epidemic_diarrhea_virus at C6 level 1 because "while this disease did have an effect when it first arrived in the US, it is now endemic across the industry and is not producing any market effects" -- that is the endemic state, which is what C6 scores for an agent already here. SADS-CoV has never arrived, so there is no endemic state to score and the incursion is the only thing there is. The two rulings are the same rule applied to agents at different stages. NOTE FOR THE PASS: this is the second exotic enteric coronavirus scored on the PED 2013/14 precedent, after his C3 level 4 ruling in the same round -- "many farms that thought they had great biosecurity became infected with PED during the first incursion, and we would expect no different if SADS-CoV turned up in the US."
Basis. Sections 28.6.1 and 28.6.4 describe outbreaks in China in 2017, 2019 and 2021 killing tens of thousands of piglets, followed by national surveillance of 1365 samples across 23 provinces. No trade measure, movement control or consumer response is recorded from any of them, and SADS-CoV is not a WOAH-listed disease.
How this level was decided
INFERRED, and it passes the precedent test in SCORING/market_impact on observation rather than inference -- something has happened three times, in a major pig-producing country, and no market consequence was recorded. Level 1. FLAGGED, AND THIS IS THE ONE PLACE THE PRECEDENT MAY NOT TRANSFER: SADS-CoV is a bat-origin coronavirus whose nearest relatives are in Chinese horseshoe bats, and the word coronavirus has carried unusual public salience since 2020. A US incursion of a bat coronavirus in pigs would not necessarily behave the way the Chinese outbreaks did, whatever the biology says.
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. ch28 28.6.10: "Currently, there are no vaccines against SADS-CoV or approved drugs to treat the infection." 28.6.6: mortality up to 90% in suckling piglets five days old or younger, with piglets dying two to six days after onset. SECOND SOURCE, puente_2026, which describes no treatment and adds a control caution: for SADS-CoV "the use of controlled feedback is strongly discouraged; intentional exposure to uncharacterised intestinal material carries the extreme risk of amplifying the virus, propagating undetected co-infections and providing the optimal environment for novel recombination events".
How this level was decided
Level 3. No treatment exists anywhere, stated outright, and the outcome one would act on is 90% mortality in the first days of life. Both halves of level 3, and the same reading as the other three enteric coronaviruses in this chapter. Corroborated 2026-09-04, and the new source sharpens why an absent treatment matters here: the maternal-immunity workaround used for PEDV and TGEV -- planned feedback exposure -- is specifically discouraged for SADS-CoV, so the toolkit is smaller than for the others. Level 3 unchanged.
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. ch28 28.6.10: "Currently, there are no vaccines against SADS-CoV or approved drugs to treat the infection." Two groups have attenuated the virus by serial passage in Vero cells -- to passage 83 and passage 100 respectively -- but "the immunogenicity of candidate live attenuated vaccines will require evaluation in pigs". SECOND SOURCE, puente_2026: "the lack of commercially available, universally effective vaccines for newly emerging agents (such as SADS-CoV, SeCoV and PDCoV) leaves global herds immunologically naive and highly vulnerable to outbreaks."
How this level was decided
Level 3. No vaccine exists in the United States or anywhere else, and the disease would plainly justify one, having killed roughly 30,000 piglets across three Chinese outbreaks. The target is tractable: two independent groups have already produced attenuated candidates by serial passage, and they are awaiting evaluation in pigs rather than awaiting a discovery. Needed but not available. Corroborated 2026-09-04 by a source that names the absence as a gap. Level 3 unchanged.
Levels and evidence are generated from data/assignments/sads_cov.yml; the overview is authored in data/overviews/sads_cov.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.