Not all naturally occurring viruses that cause human disease are PPPs. A naturally occurring pathogen is not a PPP unless it is likely to spread uncontrollably and cause moderate to severe disease and/or mortality in humans. A pathogen may not meet these criteria for transmissibility and pathogenesis due to barriers arising from its route of transmission; present levels of population immunity; or the availability of, access to, and effectiveness of community mitigation measures and medical countermeasures – as discussed in Section B.2 of the
Implementation Guidance. Although certain viruses are not PPPs in their naturally occurring forms, experiments may be subject to Category 2 oversight (as described in Section 4.2.1 of the
Policy) if these are reasonably expected to result in adaptation of those pathogens to circumvent these barriers to allow wide and uncontrollable spread and moderate to severe pathogenesis.
The Policy further defines a pathogen with enhanced pandemic potential (PEPP) as resulting from experiments that enhance a PPP’s transmissibility or virulence, or disrupt the effectiveness of pre-existing immunity, such that it may pose a significant threat to public health, the capacity of health systems to function, or national security. Furthermore, any experiment that is reasonably anticipated to modify a non-PPP to result in a pathogen that meets the transmissibility and pathogenesis definitions of a PPP is also subject to Category 2 oversight.
The Implementation Guidance provides examples of several agents that are not considered PPPs in their naturally occurring forms today but have the potential to become PPPs or PEPPs through certain experimental modifications. These would be subject to Category 2 oversight. Examples include Ebola virus, SARS-CoV-2 Omicron lineage – given population immunity as of 2024 – and Highly Pathogenic Avian Influenza (HPAI) H5 and H7 subtypes. As described in the Implementation Guidance, these agents are not currently considered PPPs because they either do not typically cause moderate to severe disease (as is the case with SARS-CoV-2) or do not currently demonstrate wide and uncontrollable spread (as is the case with HPAI and Ebola viruses). However, these agents would indeed require Category 2 oversight when subject to experiments that are reasonably anticipated to enhance transmissibility, virulence, toxicity, stability, host range, tropism, or susceptibility to preventative measures or treatments in a manner that results in a PPP or PEPP. Novel viruses that could be modified to generate a PPP or PEPP, such as novel bat-related coronaviruses, could similarly require Category 2 oversight if subject to these experiments. Finally, in addition to considering whether certain experiments may result in the need for Category 2 oversight of research involving Ebola, SARS-CoV-2, and some strains of H5N1 influenza viruses, these agents are included among the group of viruses that need to be considered for Category 1 oversight (per Section 4.1 of the Policy).