Porcine Kobuvirus
LEVELS: Highly unlikely; No human illness; Already in the herd; Reference or research laboratory required; Negligible; Negligible; Little; Available, or not needed
| Register id | porcine_kobuvirus |
| Type | virus |
| Scientific name | Porcine kobuvirus |
| NCBI taxid | 1156769 |
| Evidence | 5 document(s) |
| Assigned | 2026-09-06, against criteria version 093366e352a2 |
Overview
Porcine kobuvirus is a picornavirus that is very common in pigs — 90% of pigs under three weeks old at one index farm, 99% of Thai piglets, 30% of healthy Chinese pigs, and detected on every farm in a Dutch study of healthy animals, where it appeared at two weeks of age and cleared quickly after weaning. Its interest lies in what it apparently does not do. A systematic review looking specifically at whether it causes gastrointestinal disease concluded there is a lack of good evidence that it does, a case-control study found no association with neonatal diarrhoea, and what research exists indicates a limited ability to cause diarrhoea at all. Field data point the same way: pigs positive for both kobuvirus and PED virus were mostly sick, while pigs positive for kobuvirus alone were mostly healthy, suggesting an opportunist rather than a primary pathogen. It was originally discovered by accident, as a non-specific PCR product in an assay looking for something else, and detection still depends on laboratory-built assays. It is about 60% identical to the human kobuvirus, Aichi virus, which places them in different species; no human infection with the pig virus is described.
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, no evidence of zoonotic transmission between pigs and humans. FYI - I have uploaded several papers into the inbox relative to this group of viruses. We need to have a quick scan to ensure they do not change your or my assigned levels before we signoff."
Basis. ch36 36.7: porcine kobuvirus is "approximately 60% identical at the nucleotide sequence level to the Aichi virus", the human kobuvirus, which places them in different species. The section records no human infection with the porcine virus. shic_2021_pkv: "Kobuviruses of humans are genetically distinct from PKV, and PKV has never been isolated from a human diarrhea case." "Aichi virus causes gastroenteritis in humans."
How this level was decided
INFERRED from the chapter structured silence, with the sequence divergence from the human kobuvirus as supporting context -- 60% nucleotide identity is a different virus, not a variant. Level 1. Level 1 confirmed, and the distinction is clean: the human kobuvirus is a genetically distinct agent, and porcine kobuvirus has never been recovered from a human case.
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, no evidence of zoonotic transmission between pigs and humans."
Basis. No human disease from porcine kobuvirus is described in ch36 36.7. shic_2021_pkv: "PKV has never been isolated from a human diarrhea case."
How this level was decided
INFERRED. C2 scores level 1 whenever the agent does not cause disease in people. Level 1 confirmed.
C3 Herd introduction risk
Effort required to keep the agent out of the herd
Already in the herd: Present in most herds, or carried by pigs themselves, so there is no introduction event to prevent
Basis. de Groof 2025, in clinically healthy pigs on seven Dutch commercial farms: "Rotavirus A, Porcine Kobuvirus, Enterovirus G and Porcine Astrovirus 3 and 4 were first detected at two weeks of age", and "Porcine Kobuvirus was detected by nanopore sequencing in all farms, but it cleared quickly after weaning". Zang 2023: "PKV was highly prevalent in Chinese swine herds during 2018-2022." ch36 36.7 records 60% at the index Hungarian farm, 90% of pigs under three weeks, 99% in Thai piglets and 30% of healthy Chinese pigs. shic_2021_pkv: "Prevalence in domestic pigs ranges from 13-99%." "In the United States, PKV has been detected in feces from nursing piglets in Ohio and intestinal contents/feces from piglets in 15 different states. PKV is likely widespread in U.S. swine." "Wild boars might be a source of infection for domestic swine."
How this level was decided
Level 1 unchanged and now supported across three continents and four studies. Detected on ALL SEVEN farms in a study that selected for herds with almost no post-weaning diarrhoea, and acquired at two weeks of age. Carried by the pigs themselves, so there is no introduction event to prevent. Level 1 confirmed -- detected in 15 states and described as likely widespread in US swine.
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
CONFIRMED by Eric. The assignment reached this level from the evidence, and he has reviewed and ratified it.
Confirmed by Eric. "l3, primers described but test would not necessarily be available at all local/regional labs"
Basis. de Groof 2025 built its own assay rather than buying one: "The Porcine Kobuvirus (PKoV) RT-qPCR was designed based primers/probe from Zhou et al." ch36 36.7 records that PKV was originally found inadvertently, as "a nonspecific PCR product" in an assay looking for porcine sapovirus, and that prevalence work since has used "RT-PCR using PKV-specific primers". shic_2021_pkv: "Kobuviruses including PKV are difficult to propagate in vitro." "Reverse transcriptase polymerase chain reaction (RT-PCR) assays are used to detect PKV in both feces and serum. PKV RNA has also been detected in oral fluids." "Serum neutralization tests have been described for Aichi virus and PKV."
How this level was decided
MOVED L2 -> L3, agreeing with Eric's ruling of 2026-08-31: "l3, primers described but test would not necessarily be available at all local/regional labs." The new papers show exactly the pattern the reworded criterion is about -- a research group implementing published primers for its own study, which is not the same as a diagnostic laboratory offering the test. Nothing here is a service anyone can request. Level 3 confirmed. RT-PCR is in use on real sample types including oral fluids, so not level 4; but the virus does not culture and nothing indicates routine diagnostic availability.
C5 Production cost
Financial impact on the infected farm's cost of production
Negligible: No measurable effect on cost of production
CONFIRMED by Eric. The assignment reached this level from the evidence, and he has reviewed and ratified it.
Confirmed by Eric. CONFIRMED. "c5l1, no evidence thus far that the agent causes significant clinical disease in pigs"
Basis. Eriksen 2023, a systematic review asking this exact question: "there is a lack of good evidence supporting the idea that PKV causes gastrointestinal disease", "A case-control study showed that PKV was not associated with neonatal diarrhea", and "the sparse research available did indicate that PKV has a limited ability to cause diarrhea". Zang 2023, from field data: "Most PKV and PEDV double-positive pigs were clinically diseased, while most PKV-positive but PEDV-negative pigs were clinically healthy, suggesting that PKV is unlikely to be a direct gastroenteritis-causing virus but a potential opportunistic pathogen." de Groof 2025 found it on all seven farms of clinically healthy pigs. shic_2021_pkv: "PKV has been associated with diarrhea in pigs, but it is also found in healthy animals. Most clinical cases involve mild diarrhea. However, outbreaks with high morbidity and mortality have occurred, particularly in piglets. Disease is less common in older animals. One experimental study has confirmed PKV as a cause of diarrhea and pathogenic lesions in piglets." "Co-infection with PKV and other enteric pathogens of swine is very common."
How this level was decided
Level 1 unchanged but now SUPPORTED rather than inferred, and this is the largest gain of the round. The previous score reasoned from ch36 reporting that no causal role had been demonstrated -- an absence. Three independent lines now say it positively: a systematic review that looked for the evidence and did not find it, a field study separating PKV-alone from PKV-plus-PEDV and finding the PKV-alone pigs healthy, and a healthy-herd virome survey finding it everywhere. NOTE, and Eriksen says it explicitly so it should not be lost: "The absence of such documentation does not mean that we can conclude the opposite: that PKV is not causing gastrointestinal disease." Level 1 records what the evidence supports, not a proof of harmlessness. LEVEL 1 HELD, AND FLAGGED, because the new source is the strongest evidence the folder has ever held that this agent does something. It reports outbreaks with high morbidity and mortality in piglets, and an experimental study confirming PKV as a cause of diarrhoea and lesions -- which is causation, not association, and is more than most of the enteric picornaviruses in this register can show. Held at 1 because the same page says most clinical cases are mild, the virus is found in healthy pigs, and co-infection is very common, so the typical situation is still subclinical carriage. If Eric reads the confirmed causation plus high-mortality outbreaks as the entry's typical picture, this is a 2.
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, the agent is known to the industry and probably widespread if we look hard enough. There is no reason to think the market would react to a diagnosis"
Basis. Section 36.7 records no trade measure, movement control or consumer response. shic_2021_pkv: "PKV is not an OIE-listed disease. There are no restrictions for importation of animals from countries or zones affected by PKV."
How this level was decided
INFERRED. A ubiquitous enteric virus with no demonstrated causal role in disease has no route to pork supply or demand. Level 1. Level 1 confirmed on a direct statement.
C7 Treatment potential
Potential for treatment to improve outcomes
Little: Effective pathogen-directed treatment is available and works, or animals recover acceptably without it
CONFIRMED by Eric. The assignment reached this level from the evidence, and he has reviewed and ratified it.
Confirmed by Eric. CONFIRMED. "c7l1, no significant clinical disease from infection so there is no imperative for a treatment"
Basis. Eriksen 2023 finds no good evidence that PKV causes gastrointestinal disease. Zang 2023 concludes it is "unlikely to be a direct gastroenteritis-causing virus but a potential opportunistic pathogen". No antiviral is described for it anywhere in the folder. shic_2021_pkv: "There is no treatment for pigs infected with PKV."
How this level was decided
Level 1 unchanged, now supported rather than inferred. C7 asks how much better outcomes would be with a treatment, and the second clause of level 1 holds on evidence rather than on silence: there is no established adverse outcome to improve. Level 1 held.
C8 Vaccine availability
Availability of effective vaccines or bacterins
Available, or not needed: Effective vaccines are widely available in the US or secured for national outbreak response, or the disease does not clinically or economically justify vaccinating
CONFIRMED by Eric. The assignment reached this level from the evidence, and he has reviewed and ratified it.
Confirmed by Eric. CONFIRMED. "c8l1, no significant clinical disease from infection so there is no imperative for a vaccine"
Basis. No vaccine is described for porcine kobuvirus in ch36 36.7. shic_2021_pkv: "There is no PKV vaccine." "There are no vaccines for any kobuvirus." "The role of PKV as a swine pathogen remains unclear."
How this level was decided
INFERRED. No vaccine exists and none is warranted for a virus with no demonstrated causal role in disease. Level 1 on the second clause. Level 1 held -- role as a pathogen unclear, so no imperative.
Levels and evidence are generated from data/assignments/porcine_kobuvirus.yml; the overview is authored in data/overviews/porcine_kobuvirus.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.