Interim U.S. Guidance for Containment in Areas with Ongoing Poliovirus Circulation

Applicable to non-poliovirus essential facilities (non-PEFs) and facilities (e.g., wastewater utilities, healthcare providers) that collect, handle, or store materials from areas known or suspected to have circulating polioviruses.


A U.S. paralytic polio case was identified in a person in Rockland County, New York, in July 2022. Vaccine-derived poliovirus type 2 (VDPV2) was detected in subsequent local wastewater samples from multiple counties in the surrounding geographical area. The polioviruses identified from the New York paralytic polio case and wastewater samples meet WHO’s criteria for circulating vaccine-derived poliovirus.

The NAC interim guidance is based on the World Health Organization (WHO) Global Action Plan, 4th edition (GAPIV) and Potential Infectious Materials (PIM) Guidance documents. It outlines measures to mitigate the risks that VDPV PIM poses to personnel, the environment, public health, and the global eradication of poliovirus.

While not all PIM contains PV, WHO considers the possibility that PIM could contain PV to be a significant risk to the environment and community, if not addressed properly.

Interim guidance documents:

Additional guidance:

General Guidance


  • Facilities tasked with collecting, handling, storing, and transporting vaccine-derived poliovirus (VDPV) potentially infectious materials (PIM). This applies to laboratories and facilities such as
    • those that treat human waste and sewage,
    • healthcare providers,
    • public health laboratories,
    • vaccine producers,
    • research laboratories,
    • clinical laboratories,
    • storage facilities, and
    • environmental testing laboratories that perform these activities with PIM.
  • Facilities that collect, handle, store, and/or transport VDPV PIM are not required to be a poliovirus essential facility (PEF) or implement high containment requirements at this time.


  • VDPV PIM include materials and samples collected at a time and place where VDPV is known or suspected to be circulating and may contain poliovirus.
  • Stool, upper respiratory secretions, concentrated sewage, wastewater, and their derivatives (e.g., stool suspensions, extracted nucleic acid) collected and retained for thirty (30) days or more from VDPV PIM geographic areas are considered VDPV PIM and reported to the NAC.  ​
  • Identification of any presumptive PV-positive samples must be reported to the NAC as “infectious materials” within seven (7) days of detection. Presumptive PV-positive samples are samples that test positive but are not confirmed by CDC.

Where and When

The purpose of defining the geographic areas is to describe areas where there is evidence of virus circulation. Virus circulation is identified by more than one detection. More than one detection indicates a transmission event has taken place.

This is a dynamic situation. The United States is the first country with advanced sanitation and high polio vaccination coverage to address the issue of defining a geographic area.

VDPV1 PIM geographic areas are defined as:

  • Two or more CDC-confirmed, VDPV-positive wastewater (WW) samples from
    1. one sewershed more than two months apart2, or
    2. at least two non-overlapping sewersheds with more than one CDC-confirmed, genetically related VDPV-positive WW sample. 3

We will consider establishing upstream wastewater sampling sites to narrow a multi-county sewershed or a large sewershed within a single county.4

  • A county with two CDC-confirmed, genetically linked VDPV-positive clinical specimens from two unrelated (do not share the same household) persons.
  • Further consideration is given to determine when the time of circulation ended based on the time since the last detection in a clinical specimen or WW. Currently, we propose six months following the last detection of VDPV in WW or detection in a clinical specimen. We will refine this period as we learn more about cVDPV in the U.S.

Only stool, upper respiratory secretions, concentrated sewage, wastewater, and their derivatives (e.g., stool suspensions, extracted nucleic acid) collected and retained for thirty (30) days or more in VDPV PIM geographic areas are considered VDPV PIM and reported to the U.S. NAC.

Identification of any presumptive PV-positive samples (i.e., tested positive but not CDC confirmed) must be reported to U.S. NAC as “infectious materials” within seven (7) days of detection.

Other areas of the U.S. with no detection of PV in human or WW samples are designated as “non-PIM” geographic areas.

Non-PIM geographic areas will be defined as:

  • No detection of CDC-confirmed PV (as defined in footnote 2) in WW samples or any human detection (positive clinical detection).
  • Stool, upper respiratory secretions, concentrated sewage, wastewater, and their derivatives collected and retained in non-PIM geographic areas are neither considered PIM nor reported to the U.S. NAC.
  • For containment purposes, based on WHO’s guidance, if new PV-positive WW samples as defined in 1a and 1b are detected in an area(s) designated as “non-PIM”, the area(s) is re-classified as “VDPV PIM” geographic areas.

1 Applies to VPDV type 2 (≥6 nucleotide changes in VP1), VDPV type 1, or type 3 (>10 nucleotide changes in VP1)

2 Two genetically linked PV positives more than months (approximate shedding period is 4-8 weeks) apart from one sewer shed suggests at least two different people shedding and community-level transmission.

3 More than one genetically linked PV positives in separate sewer sheds suggests at least two different people shedding and community-level transmission

4 Global Polio Eradication Initiative, Standard Operating Procedure “Responding to A Poliovirus Event or Outbreak”, March 2022, version 4, page 8. Standard-Operating-Procedures-For-Responding-to-a-Poliovirus-Event-Or-Outbreak-20220905-V4-EN.pdf (

Guidance Strategies for Collection, Handling, Storage, and Reporting

Facilities should implement strategies to mitigate the risks to personnel collecting, handling, storing, and/or transporting VDPV PIM.

  • Assess the polio vaccination status of those handling PIM and offer vaccination when indicated to complete the adult series. Those who do not know their polio vaccination status may be offered a polio vaccination booster. Polio Vaccination Recommendations
  • Ensure appropriate standard safety precautions (e.g., personal protective equipment, training, handwashing, waste disposal) are in place for workers handling PIM.
  • Use of personal protective equipment that considers oral and mucosal membrane protection by all workers handling PIM.
  • Direct specific questions about protecting workers to the relevant state health departments, Occupational Safety and Health Administration (OSHA), National Institute for Occupational Safety and Health (NIOSH), and Environmental Protection Agency (EPA) guidance.
  • Non-laboratory workers should consider CDC guidelines for collecting and handling wastewater and COVID
  • Risk assessment of specific procedures being used or job-specific analysis.
  • Use only methods validated to inactive poliovirus for extraction of materials. Click here. [PDF – 1 MB]
  • Concentration of PIM and/or extraction of PIM should be performed in primary containment (i.e., certified biosafety cabinet).
  • Submit a U.S. NAC Poliovirus Inventory Survey and maintain an accurate inventory (facilities retaining PIM for 30 days or more or facilities with PV presumptive positives).
  • Report any changes in PIM inventory to the U.S. NAC at
  • Segregate PIM from non-PIM.
  • Secure samples in a locked freezer or laboratory, limit access
  • Ensure appropriate biosafety measures are in place (e.g., good laboratory/microbiological practices, and documentation and validation of methods/standard operating procedures (SOPs).

Facilities handling human waste or sewage should consult the EPA Wastewater Sampling and CDC Guidance for Reducing Health Risks to Workers Handling Human Waste or Sewage documents.

Non-laboratory facilities collecting respiratory samples should review the CDC Interim Guidelines for Collecting and Handling of Clinical Specimens for COVID-19 Testing.

  • Report if materials are retained for ≥30 days: Stool, upper respiratory secretions, concentrated sewage, wastewater, and their derivatives (e.g., stool suspensions, extracted nucleic acid).
  • Report within 7 days: Identification of any presumptive PV-positive samples (i.e., tested positive but not CDC-confirmed).
  • Report here.
  • Unneeded or nonessential materials are strongly encouraged to be destroyed, inactivated, or returned to the start of the wastewater treatment process (i.e., return to the treatment train)​.
  • Complete the attestation form and submit​ it to U.S. NAC to maintain the current national ​inventory of all PV materials (includes ​extracted nucleic acids that are unneeded).
  • Click here for the NAC Destruction Attestation Form
  • Transfer of infectious material (e., poliovirus-positive samples) to a U.S. PEF when CDC-confirmatorytesting is complete.​ Extracted nucleic acids may be retained by a non-PEF ​if the extraction was performed using methods that have been validated to inactivate PV.
  • Transfer of PV-positive materials must be reported to the U.S. NAC.
  • Click here for the Material Transfer Form

Contact the U.S. NAC for additional guidance.

Click here for more information on containment guidance for facilities.