Porcine Epidemic Diarrhea Virus
LEVELS: Highly unlikely; No human illness; Extraordinary biosecurity required; Laboratory-dependent; Substantial; Negligible; Substantial; Available but inconsistent
| Register id | porcine_epidemic_diarrhea_virus |
| Type | virus |
| Scientific name | Porcine epidemic diarrhea virus |
| NCBI taxid | 28295 |
| Evidence | 2 document(s) |
| Assigned | 2026-09-04, against criteria version 093366e352a2 |
Overview
Porcine epidemic diarrhea virus is a coronavirus that causes vomiting and severe watery diarrhoea in pigs of all ages, with mortality approaching 100% in piglets under a week old. It was first recognised in Europe in the 1970s and was a manageable problem for decades, until highly virulent strains emerged in China in 2010 and reached the United States in April 2013. What followed is the reference case for what a new enteric virus can do to a naive population: nearly seven million piglets died in 2013-2014, an estimated 3-6% of the US pig crop, and by 2017 the virus had reached 39 states. Two broad groups circulate — the classical strains present since the 1970s, and the emerging strains that include both the highly virulent variants and milder ones distinguished by small insertions and deletions in the spike gene. The disease it causes is clinically indistinguishable from transmissible gastroenteritis, so laboratory confirmation is essential. It continues to cause sporadic outbreaks in both previously affected and naive herds, and control depends on biosecurity, feed and transport hygiene, and deliberately exposing or vaccinating sows so that piglets receive protective antibody in milk.
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. "PEDV is only infectious for swine and does not play a known role in public health." (ch28 sec 28.3.3, p.593)
How this level was decided
Re-read against the corrected "from pigs" label on 2026-08-27; level 1 unchanged, and it now fits BETTER than before. The old label read "no evidence that the agent infects humans"; the new one reads "no evidence that pigs transmit the agent to humans". The chapter states both at once -- PEDV is only infectious for swine -- so the cell is unambiguous either way.
C2 Zoonotic impact
Severity of human illness caused by the agent
No human illness: Agent does not cause illness in people
Basis. "PEDV is only infectious for swine and does not play a known role in public health." (ch28 §28.3.3)
How this level was decided
Follows from the same statement -- an agent that does not infect people causes no human illness.
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. "The main route of PEDV transmission is direct or indirect fecal-oral transmission. Contaminated equipment, feed and feed ingredients, transport, or personnel may serve as vehicles." "Evidence of PEDV aerosol transmission has been reported in some, but not other studies." (ch28 §28.3.4) SECOND SOURCE, puente_2026, which supplies the quantities ch28 does not: PEDV "can remain viable in faeces or slurry for up to 2 weeks at 25C and up to 28 days at 4C and survives in dry and wet feed for several days", shedding runs "3-6 weeks and extend beyond clinical resolution, resulting in convalescent carriers", and the infectious dose required to initiate infection is low. On the introduction event itself: "Source tracking analyses pointed flexible containers used in international raw material transport as the most probable source for viral introduction into the continent." On what exclusion therefore takes: "the implementation of feed mitigation strategies, such as chemical treatments, extended holding times or thermal processing, and stringent equipment sanitisation, are essential interventions."
How this level was decided
MOVED L3 -> L4 on 2026-09-01 by the five-level rework. The source is other pig herds -- the chapter says the role of wild boar in maintenance is unknown rather than established, which is what keeps it off L5 -- but the 2013 US epidemic moved on feed and feed ingredients, and the response was thermal treatment and holding times rather than tighter quarantine. Feed biosecurity of that kind is the new L4 named clause. 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. CORROBORATED AND STRENGTHENED 2026-09-04. The level 4 argument was previously carried by ch28's brief mention of feed and feed ingredients as vehicles; puente_2026 makes it the centre of the account -- an international feed-container route as the probable means of entry to the continent, low infectious dose, weeks of environmental survival, and shedding that outlasts clinical signs. Its own list of required measures is thermal or chemical feed treatment plus extended holding times, which is the named level 4 clause almost word for word. This cell is now supported by two independent sources and no longer rests on the 2013 epidemic alone.
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
CONFIRMED by Eric. The assignment reached this level from the evidence, and he has reviewed and ratified it.
Confirmed by Eric. CONFIRMED. "l2, straightforward to diagnose"
Basis. "Diagnosis should be made based on both clinical signs and laboratory detection of viral RNA... the most widely used laboratory diagnostic method is RT-PCR." "PEDV infections must be differentiated from TGEV, TGEV/PEDV recombinant, PDCoV, and SADS-CoV infections using laboratory testing." (ch28 §28.3.8)
How this level was decided
Clinical signs do not distinguish PEDV from the other enteric coronaviruses, so laboratory confirmation is required -- but by RT-PCR, which regional veterinary diagnostic laboratories run routinely. Not a reference-laboratory agent.
C5 Production cost
Financial impact on the infected farm's cost of production
Substantial: Severe losses cause a major and potentially unsustainable increase in cost of production
Basis. "From 2013 to 2014, PEDV killed almost seven million piglets in the United States." "Piglets up to 1 week of age may die from dehydration and mortality ranges from 50 to 100%." (ch28 §28.3.4, §28.3.6) SECOND SOURCE, puente_2026, on the scale: "The virus explosively spread across the United States, affecting over 5500 farms in 25 states within the first year and extending to Canada, Mexico, Peru, the Dominican Republic, Colombia, and Ecuador. Over 50% of United States pig farms were infected within 2 years since the first description." On the clinical outcome: mortality "often approaching 80%-100%" in piglets under one week, against "1%-3%" in weaned pigs and adults.
How this level was decided
Near-total mortality in the youngest piglets and seven million dead in two years is a major and potentially unsustainable increase in cost of production for an affected farm. Corroborated 2026-09-04 with the farm-level denominator ch28 lacked: more than half of US pig farms infected within two years. Level 4 unchanged.
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
INFERRED — reasoned, not stated. The evidence implies this level rather than stating it. The reasoning is below.
Corrected by Eric from L3 Significant disruption. Reason: "c6l1, 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" [MERGED 2026-09-01. This cell had been recorded twice and YAML was silently keeping only this copy. Eric stated the same ruling on an earlier sheet, 2026-08-28, in these words: "c6l1 is correct for the reason i state above."]
Basis. "From 2013 to 2014, PEDV killed almost seven million piglets in the United States. By January 2017, PEDV had spread to 39 US states." (ch28 §28.3.4)
How this level was decided
INFERRED. The chapter documents the scale of loss but says nothing about pork or pig market disruption, which is what this criterion asks. Seven million piglets is roughly a week of US production, lost over two years, which implies a material supply effect measured in months rather than weeks. Level 3 is a reasoned inference from the production figures, not a reading of the text.
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 at L3, with a reservation recorded: "I guess we should make this C7L3. Does make me wish for a different level... PED+newborns=dead and not even a chance to treat, PED+juveniles=diarrhea, most recover but not perfectly, PED+older pigs and adult=a bit of diarrhea followed by complete recovery in a few days. So what is the right level?? ... Tricky, any ideas would be appreciated but we will leave as C7L3 for now." The age-structure problem is general, not a PEDV quirk -- see the open question in TODO.md.
Basis. The section describes control entirely through biosecurity, feedback and vaccination. No pathogen-directed treatment is mentioned anywhere. (ch28 §28.3.10) SECOND SOURCE, puente_2026, which likewise describes control entirely through biosecurity, feed mitigation, vaccination and maternal immunity by feedback exposure, and names no pathogen-directed treatment anywhere.
How this level was decided
INFERRED. The absence of any treatment discussion supports "no effective treatment is available". Whether outcomes would meaningfully improve if one existed is a judgment: piglets die of dehydration within days, so an effective antiviral plausibly would help. The evidence supports the first half of level 3 and not the second. Corroborated 2026-09-04: a second full review of the group describes no antiviral either, so the first half of level 3 is now stated by two sources. The second half -- that outcomes would meaningfully improve -- remains the judgment it was, which is why this cell stays INFERRED. Eric ruled it at level 3 on 2026-08-26 while recording the age-structure reservation, and the standing note SCORING/treatment_potential resolves it: score the neonate.
C8 Vaccine availability
Availability of effective vaccines or bacterins
Available but inconsistent: Commercial or autogenous vaccines exist in the US but protection may be inconsistent
Basis. "Two commercial vaccines are available in the United States... Its use in PEDV-naive pregnant sows showed low piglet protection in two studies and low PEDV VN antibody titers in sow milk... It did not induce PEDV VN antibodies in milk of PEDV-naive vaccinated sows." (ch28 §28.3.10) SECOND SOURCE, puente_2026, which lists PEDV among the agents that DO have vaccines while naming "the lack of commercially available, universally effective vaccines for newly emerging agents (such as SADS-CoV, SeCoV and PDCoV)", and sets as a research priority "the development of next-generation mucosal vaccines and defining the immunological basis of cross-protection against rapidly evolving, recombination-driven variants". It also notes that in Asia "the widespread use of inactivated and attenuated vaccines in the region seems to have favoured virus persistence through the emergence of new variants".
How this level was decided
Vaccines exist and are licensed in the US, and the chapter states plainly that protection is inconsistent. That is the level 2 definition almost verbatim. Corroborated 2026-09-04. Puente separates PEDV from the agents with no vaccine at all, and its stated priority is a BETTER vaccine rather than a first one -- which is level 2, available but inconsistent, from the other direction.
Levels and evidence are generated from data/assignments/porcine_epidemic_diarrhea_virus.yml; the overview is authored in data/overviews/porcine_epidemic_diarrhea_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.