RESTON VIRUS (RESTV)
LEVELS: Highly unlikely: No controls necessary; Occupational exposure risk: Non-foodborne transmission pathway(s) that are strongly associated with occupational exposure and can lead to human infection; Highly effective: Routine on-farm biosecurity measures are effective in preventing farm-to-farm transmission; Moderate: Clinical signs not unique but existing tests available at local/regional laboratory(s); Minor: Low prevalence, typically non-lethal infection with recovery very likely; Prolonged disruption: Measureable negative effect on demand for more than 6 months when disease occurs on one or more farms; Minimal risk: Agent inherently unlikely to develop clinically important resistance to antibacterial or antiviral treatments; Minimal risk: Antibacterial or antiviral treatments rarely occur, or are typically limited to short-course individual animal therapy; No availability: Effective treatments not currently available in the US (or have not been developed); No availability: Effective vaccines not currently available in the US (or have not been developed); Highly likely: Can be eradicated using existing tools and knowledge
OVERVIEW
Reston virus (RESTV) is an orthoebolavirus within the family Filoviridae, first discovered in 1989 during an outbreak in cynomolgus macaques imported from the Philippines to a quarantine facility in Virginia, USA. In 2008, natural RESTV infection was documented in domestic pigs in the Philippines, with subsequent detection in Chinese pigs in 2014. RESTV is the only filovirus known to naturally infect pigs. Unlike other ebolaviruses that cause severe hemorrhagic fever in humans, RESTV causes asymptomatic infection in humans—antibodies have been detected in exposed farm workers without associated illness. In pigs, experimental infections produce outcomes ranging from subclinical to severe respiratory distress, though natural infections in the Philippines were confounded by concurrent highly pathogenic PRRSV coinfection. RESTV is not present in US swine but represents a foreign animal disease of concern due to its zoonotic potential, BSL-4 classification, and the demonstrated capacity for pig-to-pig and pig-to-human transmission. The natural reservoir appears to be Asian bat species, though the specific reservoir has not been definitively identified.
FOODBORNE ZOONOTIC TRANSMISSION POTENTIAL
Level: Highly unlikely: No controls necessary
There is no evidence that RESTV transmits to humans through consumption of pork products. Human RESTV infections documented during the 2008 Philippines outbreak occurred in farm workers with direct occupational exposure to infected pigs, not through food consumption. RESTV causes asymptomatic infection in humans—seroconversion without clinical disease—further reducing any theoretical foodborne risk significance. The virus replicates primarily in respiratory tissues in pigs, and while virus has been detected in muscle tissue in some experimentally infected animals, no foodborne transmission pathway has been documented or implicated epidemiologically.
NON-FOODBORNE ZOONOTIC TRANSMISSION POTENTIAL
Level: Occupational exposure risk: Non-foodborne transmission pathway(s) that are strongly associated with occupational exposure and can lead to human infection
RESTV antibodies were detected in farm workers during the 2008 Philippines pig outbreak, confirming pig-to-human transmission occurred. However, critically, none of these seropositive workers developed clinical disease—RESTV causes asymptomatic human infection, distinguishing it from other ebolaviruses like EBOV and SUDV that cause severe hemorrhagic fever with high fatality rates. The mechanisms of human attenuation are not understood, which is why RESTV is still handled at BSL-4 despite its apparent lack of human pathogenicity. The concern remains that sustained pig-to-pig transmission could select for mutations producing human-pathogenic variants. A 2019 Philippine risk assessment rated both the probability of human RESTV occurrence and its potential pathogenicity as "moderate." Transmission to humans appears to require close occupational contact with infected pigs rather than casual exposure.
EFFECTIVENESS OF ON-FARM BIOSECURITY IN PREVENTING FARM-TO-FARM TRANSMISSION
Level: Highly effective: Routine on-farm biosecurity measures are effective in preventing farm-to-farm transmission
The natural reservoir of RESTV in Asia has not been definitively identified, but several bat species in the Philippines region have tested positive for RESTV RNA or antibodies, suggesting a wildlife reservoir that could introduce virus to pig populations independent of pig movements. Experimentally infected pigs shed high levels of virus in nasal secretions, nasal swabs, and nasal washes, with viral RNA also detected in oral swabs and blood. Pigs experimentally inoculated with RESTV can transmit virus to co-housed naive pigs, demonstrating direct contact transmission. The findings suggest droplet or aerosol transmission is possible based on respiratory shedding patterns, though long-distance airborne spread has not been demonstrated. RESTV environmental stability has not been specifically characterized but is expected to be similar to other filoviruses—susceptible to lipid solvents, phenolic compounds, 70% ethanol, and 0.5% sodium hypochlorite. The bat reservoir represents a pathway beyond standard biosecurity, though the precise mechanisms of spillover to pigs remain unclear.
DIFFICULTY OF DETECTING AND CONFIRMING INFECTION
Level: Moderate: Clinical signs not unique but existing tests available at local/regional laboratory(s)
RESTV infection in pigs produces clinical signs that overlap with common respiratory diseases, particularly PRRSV and influenza, making clinical recognition alone insufficient for diagnosis. During the 2008 Philippines outbreak, RESTV-infected pigs were coinfected with highly pathogenic PRRSV, and the specific contribution of RESTV to observed clinical signs remains uncertain. Laboratory confirmation is essential and achievable: real-time RT-PCR assays targeting the L or NP genes have been developed for detecting RESTV RNA in pig samples, and immunohistochemistry can detect viral antigen in tissues. ELISA assays detect RESTV antibodies in swine samples, though assay performance has not been fully characterized, and confirmatory testing by virus neutralization requires BSL-4 containment. Virus isolation in Vero cells produces low-level cytopathic effects in 7-10 days, with immunostaining useful for confirmation. The requirement for BSL-4 facilities for work with live virus limits routine diagnostic capacity, but molecular detection of inactivated samples can be performed under lower biosafety conditions.
FINANCIAL IMPACT ON FARM'S COST OF PRODUCTION
Level: Minor: Low prevalence, typically non-lethal infection with recovery very likely
The direct production impact of RESTV infection in pigs appears limited based on available evidence. In experimental studies, outcomes range from completely subclinical infection with no fever, respiratory disease, or skin lesions despite high tissue viral concentrations, to severe respiratory distress with tachypnea, dyspnea, and cyanosis. The variability may relate to virus isolate origin, adaptation status, or passage history. During the 2008 Philippines outbreak, severe disease and mortality were observed, but pigs were coinfected with highly pathogenic PRRSV, confounding attribution of losses to RESTV specifically. The infection profile in experimental studies is consistent with acute, self-limiting infection resolving by 28 days post-inoculation without evidence of persistence. Age-related differences have been observed, with some studies showing younger piglets having milder disease than older piglets. Overall, RESTV alone does not appear to cause catastrophic production losses, though respiratory disease in affected herds could contribute to reduced performance.
EFFECT ON DOMESTIC OR EXPORT MARKETS
Level: Prolonged disruption: Measureable negative effect on demand for more than 6 months when disease occurs on one or more farms
Detection of RESTV in US swine would trigger immediate and severe regulatory response due to its classification as a BSL-4 pathogen and its status as a filovirus with documented zoonotic transmission capacity. Although RESTV does not cause human disease, the theoretical risk of mutation toward human pathogenicity during sustained pig circulation, combined with the association of filoviruses with catastrophic human outbreaks (Ebola virus disease), would generate intense public health concern and likely consumer alarm disproportionate to actual risk. International trade partners would almost certainly impose immediate restrictions on US pork exports. Domestic movement controls, enhanced surveillance, and potential depopulation of affected premises would follow standard foreign animal disease response protocols. The market impact would be driven primarily by regulatory and public perception responses rather than direct production losses, similar to or exceeding responses to other foreign animal diseases.
PATHOGEN'S ABILITY TO DEVELOP AND SPREAD RESISTANCE
Level: Minimal risk: Agent inherently unlikely to develop clinically important resistance to antibacterial or antiviral treatments
RESTV is a viral pathogen (negative-sense RNA virus) that does not carry, acquire, or transmit antimicrobial resistance genes. The virus poses no AMR concerns regardless of disease epidemiology or management approaches. Filoviruses replicate entirely in the cytoplasm using their own RNA-dependent RNA polymerase and do not interact with bacterial resistance mechanisms.
AMR DEVELOPMENT DRIVEN BY DISEASE MANAGEMENT
Level: Minimal risk: Antibacterial or antiviral treatments rarely occur, or are typically limited to short-course individual animal therapy
No antiviral treatments exist for RESTV infection in pigs. Management of affected herds would focus on quarantine, biosecurity, and depopulation rather than therapeutic intervention. Antimicrobials might be used to address secondary bacterial respiratory infections in affected pigs, but RESTV-specific disease management does not drive antimicrobial use. Given the expected regulatory response of quarantine and depopulation for any US detection, opportunities for antimicrobial use in RESTV-affected herds would be minimal.
AVAILABILITY OF EFFECTIVE TREATMENT OPTIONS
Level: No availability: Effective treatments not currently available in the US (or have not been developed)
There are no approved antiviral treatments for RESTV infection in any species. Management in pigs is entirely supportive if attempted, though regulatory response to detection would likely prioritize quarantine and depopulation over treatment. Research into filovirus therapeutics has focused on human-pathogenic species (EBOV, SUDV) rather than RESTV given the latter's lack of human pathogenicity. No specific therapeutics have been developed or tested for RESTV in swine.
AVAILABILITY OF EFFECTIVE VACCINES OR BACTERINS
Level: No availability: Effective vaccines not currently available in the US (or have not been developed)
No vaccines are available for RESTV in pigs. The infrequency of natural infection in swine (documented only in the Philippines and China) and the lack of severe pig disease in most experimental studies have not justified vaccine development investment. Human RESTV vaccines have not been prioritized given asymptomatic human infection. If RESTV were to emerge as a significant threat to pig production or as a pathway for human-pathogenic variant emergence, vaccine development could be pursued using platforms developed for other ebolaviruses, but no such products currently exist for swine.
FEASIBILITY OF ERADICATING THE DISEASE FROM THE US
Level: Highly likely: Can be eradicated using existing tools and knowledge
RESTV is not currently present in US swine populations. If introduced, eradication would be feasible using standard foreign animal disease response measures: rapid detection through enhanced surveillance, quarantine of affected premises, depopulation and disposal, cleaning and disinfection, and movement controls. RESTV is susceptible to common disinfectants (70% ethanol, 0.5% sodium hypochlorite, lipid solvents, phenolic compounds, formaldehyde). The virus does not establish persistent infection in pigs—experimental infections resolve within 28 days. The primary challenge would be identifying and addressing the introduction source (likely imported animals or wildlife exposure in a novel geographic context). Unlike some endemic diseases, RESTV has no established US reservoir and limited capacity for sustained transmission, making elimination achievable if detected early before widespread dissemination.