Reston Virus
LEVELS: Rarely occurs; No human illness; Routine biosecurity keeps it out; Reference or research laboratory required; Minor; Temporary disruption; Little; Available, or not needed
| Register id | reston_virus |
| Type | virus |
| Scientific name | Reston ebolavirus |
| NCBI taxid | 186539 |
| Evidence | 3 document(s) |
| Assigned | 2026-09-06, against criteria version 093366e352a2 |
Overview
Reston virus is the one ebolavirus that infects pigs and the one that does not appear to make people ill. It was recognised in domestic pigs in the Philippines in 2008 and subsequently in China; its natural reservoir in Asia is unknown, though several bat species there carry viral RNA or antibody. Whether it causes disease in pigs is genuinely unresolved. Severe illness and death were seen in the 2008 outbreak, but those pigs were also infected with a highly pathogenic PRRS virus, and three experimental studies since have disagreed with each other — one found all inoculated pigs clinically healthy, another found all of them in respiratory distress by six days. Pigs do transmit it to other pigs by direct contact and possibly by aerosol, and it spreads readily once in a herd. Farm workers in the Philippines developed antibodies, so pig-to- human transmission occurred, but 1-4% seropositivity produced no illness at all: the virus infects people without causing disease and does not pose a significant public health risk. Because nobody understands why it is attenuated in humans, it is still handled at the highest biosafety level, which makes routine diagnostic work impractical. There are no means of preventing or controlling it in pigs and no vaccine is likely, given how rare infection is and how little disease it causes; the recommended response to a case is quarantine and depopulation.
C1 Zoonotic potential
Likelihood of transmission from pigs to humans
Rarely occurs: Human infection from pigs is plausible but has only rarely been reported, and specific control points are not commonly implemented to prevent transmission to humans
Basis. ch29 29.1: "In late 2008, natural infection of domestic pigs by RESTV was reported in the Philippines (Barrette et al. 2009). FOLLOW-UP STUDIES OF FARM WORKERS IN THE PHILIPPINES DETECTED ANTIBODIES TO RESTV, SUGGESTING HUMAN EXPOSURE." 29.3 states the transmission as fact: "RESTV WAS TRANSMITTED FROM PIGS TO HUMANS DURING THE 2008/2009 OUTBREAK (Barrette et al. 2009)." cfsph_2022_vhf_filovirus puts the rate on it: "Reston virus does not seem to cause disease in humans, but 1-4% OF THOSE WHO HAD BEEN EXPOSED TO EITHER CAPTIVE NONHUMAN PRIMATES OR INFECTED PIGS IN THE PHILIPPINES WERE SEROPOSITIVE." On what was in place to stop it: "SPECIFIC MEASURES TO PREVENT PIGS FROM BECOMING INFECTED WITH RESTON VIRUS IN ENDEMIC AREAS HAVE NOT BEEN ESTABLISHED." shic_2024_ebola_reston: "Antibodies to Reston virus have been detected in humans, but there are no reports of clinical illness." "Pigs can be naturally infected with Reston virus." "Reston virus should be considered a livestock pathogen with zoonotic potential."
How this level was decided
RE-READ AND HELD AT L2 2026-09-04 AGAINST THE REWORDED LABELS. ch29 29.3 states it as fact: "RESTV WAS TRANSMITTED FROM PIGS TO HUMANS DURING THE 2008/2009 OUTBREAK", with 1-4% of exposed workers seropositive. Attributed to pigs, and rare.
PREVIOUS ANSWER, kept because the evidence behind it has not changed, only the level boundary: Level 2. Human infection from pigs is not merely plausible here -- it is documented, in one outbreak, at 1-4% of exposed people, with no control point implemented against it. That is the level 2 label almost word for word: plausible but rarely reported, and specific control points not commonly implemented. THE ARGUMENT FOR LEVEL 3 is that this is an occupational exposure and the control point is identifying and depopulating the infected herd, which had not happened. I HAVE NOT TAKEN IT, on the reasoning you applied to Sarcoptes today -- "the literature overrates the potential... human infection is plausible and described, just very infrequent". One outbreak, 1-4% seroconversion, and the seropositive group includes primate handlers as well as pig workers. NOTE THAT THIS CELL AND C2 PULL IN OPPOSITE DIRECTIONS AND BOTH ARE RIGHT: the virus does move from pigs to people, and it does nothing when it arrives. Level 2 confirmed and now well supported. This is the shape L2 exists for: pigs are naturally infected, people exposed to them seroconvert, so transmission from pigs is more than plausible -- but it is documented as antibody rather than as reported clinical cases, which is "has only rarely been reported".
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, tricky one for the reasons noted and yes i agree with the need to modify the l1 description as we have sort been applying this criteria to several agents whereby 'if you try hard enough, or look hard enough' you find exposure in humans but the link to pigs as the attributable cause is weak."
Basis. ch29 29.3: "RESTV CAN CAUSE INFECTION IN HUMANS WITHOUT LEADING TO DISEASE and, therefore, DOES NOT POSE A SIGNIFICANT PUBLIC HEALTH RISK. However, because the mechanisms of attenuation in humans are not understood, RESTV is handled at Biosafety Level 4 (BSL-4)." cfsph_2022_vhf_filovirus: "An ebolavirus found in the Philippines, RESTON VIRUS, can affect nonhuman primates, THOUGH IT IS NOT KNOWN TO CAUSE ANY ILLNESS IN HUMANS", and "Reston virus DOES NOT SEEM TO CAUSE DISEASE IN HUMANS, but 1-4% of those who had been exposed... were seropositive." No human illness with RESTV is described in either document. shic_2024_ebola_reston: "Reston virus does not cause disease in humans." "Antibodies to Reston virus have been detected in humans, but there are no reports of clinical illness."
How this level was decided
Level 1, and FLAGGED -- not because the level is doubtful, which it is not, but because THIS ENTRY EXPOSES A GAP IN THE LEVEL 1 LABEL that is worth knowing about before the criteria examples are reconciled at the end. The label reads "No human disease from pigs: Pigs are not a source of human illness with this agent, EITHER BECAUSE IT DOES NOT INFECT PEOPLE OR BECAUSE IT DOES NOT REACH THEM FROM PIGS." The headline claim is exactly true of RESTV. NEITHER OF THE TWO REASONS IS. It does infect people, and it does reach them from pigs -- it simply causes no illness when it gets there, which is a third reason the label does not list. The level is still 1 because the criterion measures severity of human illness and there is none. I am recording it rather than fixing it, since you have said examples and wording get reconciled once the register is scored. NOTE ALSO THE STRUCTURAL POINT, because it is the mirror of the problem the C2 rescoping fixed on 2026-09-01: that rescoping stopped an agent scoring high on C2 while presenting no pig-attributable risk. This is the reverse -- C1 level 2 with C2 level 1, so the entry carries some weight for transmission that leads to nothing. The chapter argues that is not empty: "outbreaks of RESTV with MULTIPLE PIG-TO-PIG TRANSMISSIONS COULD RESULT IN VIRUS MUTATIONS AND THE EMERGENCE OF PATHOGENIC STRAINS able to cause disease in pigs and possibly humans." That risk has no home in any of the eight criteria. Level 1 confirmed by direct statement. Note this is the reworded level 1 doing its job -- the agent demonstrably reaches people and demonstrably does not make them ill, which the pre-2026-09-04 wording could not express.
C3 Herd introduction risk
Effort required to keep the agent out of the herd
Routine biosecurity keeps it out: Quarantine of incoming stock, transport and fomite control, cleaning and disinfection, and the usual monitoring reliably exclude it
CONFIRMED by Eric. The assignment reached this level from the evidence, and he has reviewed and ratified it.
Confirmed by Eric. CONFIRMED. "c3l3, if in the US, L3 biosecurity would be expected to exclude it from herds"
Basis. ch29 29.4.1: "RESTV emerged in domestic swine in the Philippines [2008]. Subsequently, RESTV infection in pigs in China was also reported... THE NATURAL RESERVOIR OF RESTV IN ASIA HAS NOT BEEN IDENTIFIED, BUT SEVERAL BAT SPECIES IN THE REGION have been demonstrated to have RESTV viral RNA or antibodies." On pig-to-pig spread: "PIGS EXPERIMENTALLY INOCULATED WITH RESTV CAN TRANSMIT THE VIRUS TO CO-HOUSED NAIVE PIGS... transmission by direct contact occurs and transmission via droplets or aerosols is a possibility." cfsph_2022 on how fast: "ONCE RESTON VIRUS INFECTS PIGS, IT SEEMS TO SPREAD READILY: SEROPREVALENCE WAS APPROXIMATELY 70% AMONG PIGS ON AFFECTED FARMS in the Philippines." And on exclusion: "Specific measures to prevent pigs from becoming infected with Reston virus in endemic areas have not been established, BUT NORMAL BIOSECURITY MEASURES SHOULD BE HELPFUL. As much as possible, PIGS SHOULD BE RESTRICTED FROM CONTACT WITH BATS OR NONHUMAN PRIMATES in these regions." shic_2024_ebola_reston: "Keeping pigs indoors can reduce exposure to bats, the suspected reservoir species. Biosecurity plans should consider contact with other hosts, such as infected humans and fomites." "It is not known how natural infections are acquired."
How this level was decided
INFERRED. Level 3, and it is the bat rule applied exactly as it was to Hendra and Nipah, both of which sit at level 3. The suspected reservoir is Philippine and Chinese bats, which are not on this continent, so an incursion here brings the virus and not its ecosystem; C3 is therefore scored on what the onward source would actually be in a US herd, which is other pigs by direct contact and droplet. Housing does nothing about that, so it is not level 2, and the route is exactly what quarantine of incoming stock and fomite control address. CFSPH names the level in its own words -- "NORMAL BIOSECURITY MEASURES SHOULD BE HELPFUL". NOT LEVEL 4: nothing in the folder suggests exclusion needs filtration, thermally treated feed or costly carrier testing, and the virus produces an acute infection with no evidence of persistence in any tissue at 28 days. Level 3 held. Same reasoning as ebola_virus, with one addition that argues against dropping to 2: the factsheet says outright that nobody knows how pigs acquire natural infection, so the bat route housing closes may not be the operative one.
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. ch29 29.4.4: "DESPITE THE FACT THAT RESTV HAS NOT BEEN ASSOCIATED WITH HUMAN DISEASE, WORK INVOLVING INFECTIOUS VIRUS IS RESTRICTED TO BSL-4 LABORATORIES IN MOST COUNTRIES. Standard culture techniques are suitable for RESTV, with Vero cells being the choice for virus isolation... REAL-TIME RT-PCR ASSAYS targeting the L or the NP gene HAVE BEEN DEVELOPED for the detection of RESTV RNA in samples from pigs... ELISA ASSAYS HAVE BEEN DEVELOPED to detect RESTV antibodies in swine samples, BUT THE ASSAY PERFORMANCE HAS NOT BEEN FULLY CHARACTERIZED. Other assays, such as virus neutralization, can be used to confirm ELISA results, ALTHOUGH THESE ASSAYS REQUIRE BSL-4 CONTAINMENT." On the presentation, 29.4.2: outcomes range "from absence of clinical signs to severe respiratory distress", and where signs occur they are anorexia, somnolence, tachypnea and cough. cfsph_2022: "Virus isolation is less common, DUE TO THE NEED FOR HIGH BIOSAFETY LEVEL (E.G. BSL 4) FACILITIES." shic_2024_ebola_reston: "Tests to detect Reston virus in pigs in the Philippines included RT-PCR, panviral microarray, antigen ELISA, immunohistochemistry, and virus isolation. Quantitative RT-PCR assays were used to detect Reston virus in the spleen of infected pigs in China (no confirmatory test)."
How this level was decided
Level 3. Nothing about the clinical picture points here -- it is respiratory disease indistinguishable from the commonplace, and in the one natural outbreak the pigs had highly pathogenic PRRSV as well -- so it is not level 1 or 2 on presentation. A validated assay does exist: RT-PCR was developed for pig samples and identified the 2008 outbreak. WHERE IT CAN BE RUN IS THE POINT, and it is the level 3 label: this is a BSL-4 agent in most countries, so isolation and confirmatory neutralisation are national reference laboratory work, not regional. Scored level with classical swine fever, foot-and-mouth disease and African swine fever for the same structural reason. NOTE THE ONE GENUINE WEAKNESS, which is on the serology rather than the PCR: the swine ELISA performance "has not been fully characterized", and confirming it needs BSL-4. Level 3 confirmed. Assays exist and were deployed on real outbreaks, so not level 4 -- though the parenthetical that the Chinese detections had no confirmatory test is a reminder of how thin the validation is outside a reference laboratory.
C5 Production cost
Financial impact on the infected farm's cost of production
Minor: Small and generally short-lived losses with little effect on overall 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. "c5l2, evidence that infection in pigs will cause minor disease but no higher than l2 description notes"
Basis. ch29 29.4.2, and the contradiction is the chapter's own: "During the 2008 outbreak of RESTV in domestic pigs in the Philippines, SEVERE CLINICAL DISEASE AND MORTALITY WAS OBSERVED. HOWEVER, PIGS INFECTED WITH RESTV WERE ALSO COINFECTED WITH HIGHLY PATHOGENIC PRRSV, MAKING IT UNCERTAIN AS TO WHETHER RESTV ALONE CAUSES DISEASE IN NATURALLY INFECTED PIGS." Three experiments then disagree: Marsh et al. 2011 -- "ALL ANIMALS REMAINED CLINICALLY HEALTHY, with no evidence of fever, respiratory disease, or skin lesions"; Haddock et al. 2021 -- "ALL INFECTED ANIMALS SHOWED RESPIRATORY DISTRESS BY 6 DPI, including tachypnea or dyspnea with abdominal pumping and central cyanosis"; Lewis et al. 2024 -- "a spectrum of disease, ranging from absence of clinical signs to severe respiratory distress". "THE REASONS FOR THE DIFFERENT CLINICAL OUTCOMES IN THESE THREE EXPERIMENTAL PIG INOCULATION STUDIES ARE UNKNOWN." cfsph_2022 adds the outcome: "SURVIVORS RECOVERED COMPLETELY." 29.4.6 gives the chapter's own summary: "Due to the INFREQUENCY OF INFECTION IN SWINE AND THE LACK OF DISEASE, vaccines are unlikely to be available." shic_2024_ebola_reston: "Pigs infected with Reston virus experimentally can remain asymptomatic or develop serious respiratory illness." "Clinical signs and lesions in pigs co-infected with Reston virus and PRRS virus were consistent with severe, atypical PRRS." "The prevalence of Reston virus in pigs can be very high in affected areas."
How this level was decided
INFERRED, AND FLAGGED, because the folder contradicts itself and the pass is choosing between its halves. LEVEL 2 -- small and generally short-lived losses. WHAT SUPPORTS IT: no mortality has been attributed to RESTV alone in any study, survivors recover completely, and where disease occurs it is transient respiratory illness. THE TWO RULES YOU HAVE ALREADY SET DECIDE THIS CELL, and both point the same way. First, Menangle, 2026-09: "a level is a claim about the general case, and ONE OUTBREAK CANNOT SUPPORT THE GENERAL CASE however bad that outbreak was" -- and the single RESTV outbreak was confounded by highly pathogenic PRRSV, so it is worse evidence than Menangle's was. Second, swine vesicular disease, where the pass wrote and you accepted that C5 SCORES THE DISEASE and "the stamping out that follows a detection is a REGULATORY RESPONSE to trade status, not to production loss, and is scored at C6" -- which matters here because 29.4.6 says "it would be prudent to QUARANTINE AND DEPOPULATE FARMS" and CFSPH says infected animals are euthanized. That total loss is real and it is scored in C6, not here. THE ARGUMENT FOR LEVEL 1 is the chapter's own phrase, "lack of disease". I have not taken it because two of the three experiments produced clinical disease and one produced severe respiratory distress in every pig. Level 2 held. The severe picture in the Philippines and China was in pigs CO-INFECTED with PRRSV and reads as atypical PRRS, so the loss attributable to Reston virus alone is not established -- and single infection experimentally can be asymptomatic. Worth noting the pull upward, since prevalence can be very high in affected areas.
C6 Market impact
Duration of material disruption to pork and pig markets
Temporary disruption: Material negative effect on supply or demand lasting less than a month 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. "c6l2, as with other members of this group, they are high profile and there would be regulatory involvement for a period of time"
Basis. ch29 29.4.6: "There are no mechanisms to prevent or control RESTV (or other filovirus) infections in pigs. Although the risk to humans is low, IT WOULD BE PRUDENT TO QUARANTINE AND DEPOPULATE FARMS." cfsph_2022: "Animals infected with African filoviruses are usually euthanized to keep these viruses from spreading to humans. RESTON VIRUS-INFECTED ANIMALS ARE ALSO EUTHANIZED." 29.3 records the standing public health position -- RESTV "does not pose a significant public health risk" -- and cfsph_2022 that it "is not known to cause any illness in humans". RESTV has never been reported in the Americas; the natural events are the Philippines (2008) and China, and no market consequence of either is recorded in the folder. shic_2024_ebola_reston: "Ebola virus and Reston virus are not notifiable to the U.S. Animal and Plant Health Inspection Service (APHIS)." "Meat from sick or dead animals should not be consumed, but pork from healthy pigs is safe to eat when cooked properly."
How this level was decided
INFERRED, AND FLAGGED. There is no US history to reason from, so this is scored on what would happen, which is the same footing as swine vesicular disease and Menangle. LEVEL 2 -- a material effect on supply or demand lasting less than a month. THE CALIBRATION COMES FROM YOUR OWN MENANGLE RULING, which is the closest case you have decided: "if this was diagnosed in the US (unlikely of course) it would have A TEMPORARY AFFECT ON MARKETS. It is zoonotic, unusual, and causes severe disease in both people and pigs... BAT BORNE DISEASES ATTRACT PUBLIC ATTENTION and I think we would anticipate regulatory action, even if in a single herd." Every clause of that applies here except the last: RESTV is zoonotic, unusual and bat-associated, but it causes NO human disease, and once that is said the story has nowhere to go. THE ARGUMENT FOR LEVEL 3 is swine vesicular disease, which you put at level 3 because stamping out to regain a trade status runs for months. It is weaker here: RESTV carries no equivalent trade status in the folder, and the depopulation described is a precaution rather than a route back to free status. THE ARGUMENT FOR LEVEL 4 is one word -- the virus is an ebolavirus, and "Ebola found in American pigs" is a headline that would not be corrected quickly. Level 2 held. There is an observed precedent -- the 2008 Philippine event -- so unlike Ebola this cell is scoreable. The factsheet's food-safety reassurance and the absence of any listing or notification requirement keep it at the short end.
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, little imperative for treatment development"
Basis. ch29 29.4.6: "THERE ARE NO MECHANISMS TO PREVENT OR CONTROL RESTV (OR OTHER FILOVIRUS) INFECTIONS IN PIGS. Although the risk to humans is low, it would be prudent to quarantine and depopulate farms." On outcome without treatment, cfsph_2022: "SURVIVORS RECOVERED COMPLETELY", and ch29 29.4.2 records that Marsh's inoculated pigs "all remained clinically healthy" while the infection profile was "consistent with an ACUTE INFECTION, WITH NO EVIDENCE INDICATING VIRUS PERSISTENCE IN ANY TISSUE at necropsy at 28 days post inoculation." shic_2024_ebola_reston: "There is no treatment for pigs infected with Reston virus."
How this level was decided
INFERRED, AND FLAGGED, because the chapter says flatly that nothing exists to treat this and the pass is still scoring level 1. THE GROUND IS NOT THAT TREATMENT IS NOT DONE, which your 2026-09-02 rule forbids -- it is the other clause of level 1, that ANIMALS RECOVER ACCEPTABLY WITHOUT IT. Survivors recover completely, the infection is acute and clears by 28 days with no tissue persistence, and no mortality has been attributed to the virus alone. A treatment would have little to improve. THE SECOND REASON, WHICH I PUT SECOND DELIBERATELY because on its own it would be the SVDV argument rather than a C7 argument: an infected US herd would be depopulated for public health reasons, so a pig that could be treated would be killed anyway. THE ARGUMENT FOR LEVEL 3 is Haddock 2021, where every inoculated pig reached respiratory distress with cyanosis -- if that is the typical outcome rather than the outlying one, a treatment would plainly help, and the folder cannot say which it is. 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
Basis. ch29 29.4.6, which states both the absence and the reason in one sentence: "DUE TO THE INFREQUENCY OF INFECTION IN SWINE AND THE LACK OF DISEASE, VACCINES ARE UNLIKELY TO BE AVAILABLE." The recommended response instead is "to quarantine and depopulate farms", and cfsph_2022 confirms that Reston virus-infected animals are euthanized. shic_2024_ebola_reston: "There are no Reston virus vaccines."
How this level was decided
Level 1 on the "not needed" clause, and the chapter makes the claim rather than the pass -- which is what your PCV4 rule requires, since asserting a vaccine is not needed is still a claim about the disease. Under the standing note SCORING/vaccine_availability written on 2026-09-03, TWO OF THE FOUR ROUTES TO NO IMPERATIVE APPLY HERE, and the chapter names both in the same sentence: low prevalence ("infrequency of infection in swine") and low clinical significance ("the lack of disease"). The fourth route reinforces it -- the response to an incursion would be depopulation rather than vaccination, which is the position you took on swine vesicular disease: "if the disease became established perhaps vaccine would be a useful management tool but today, the objective would be rapid [eradication]." Level 1 held.
Levels and evidence are generated from data/assignments/reston_virus.yml; the overview is authored in data/overviews/reston_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.