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Develop a Surveillance Plan: Disease Control Areas / Zones

 Area/Zone definitions are an important component of any outbreak surveillance plan because they dictate which specific Area/Zone must be established as a result of the status of premises infection (e.g. infected premises versus at-risk premises) and the subsequent surveillance actions that must be performed. These guidelines may be used in surveillance planning for commercial operations as well as for backyard populations.

What to Include

The disease control areas / zones section of a surveillance plan defines:

  1. The physical location and boundaries of the Control Area, Surveillance Zone, and Free Area, and

  2. The permissible activities in each Area/Zone that will facilitate accomplishing the immediate goals of any surveillance activities being conducted, and
  3. The length of time that each Area/Zone boundary should be maintained.

Action Items

Define boundaries of each Area / Zone - The dimensions should be developed in collaboration with other parties involved in the outbreak such as the State Animal Health Official, Federal Assistant Director (AD), and Federal Area Emergency Coordinator (AEC).

Provide maps - If possible, consult with a GIS specialist to map actual boundaries. See the Map resources in this Toolbox for contact information and resources.

Write the Disease Control Area / Zone section of the surveillance plan - Open your draft surveillance plan and modify the Disease Control Zones content. Click here to preview the template content in your browser.

More About Disease Control Areas / Zones

The primary outbreak surveillance disease Areas/Zones defined in the surveillance plan are the Control Area, Free Area, and Surveillance Zone (part of the Free Area).  The Control Area is further divided into an Infected Zone and a Buffer Zone. The Area/Zone sizes described below are specific to highly contagious diseases (HCDs), but can be used for other diseases as a starting point.

Area/Zone sizes for non-HCDs vary for each situation and depend upon input from collaborating parties. The dimensions should be developed in collaboration with other parties involved in the outbreak such as the State Animal Health Official, Federal Assistant Director (AD), and Federal Area Emergency Coordinator (EAC). See the Zones, Areas, and Premises Designations in Foreign Animal Disease Outbreak reference guide for more information on factors used to determine Control Area size.

Figure 1. Outbreak Disease Control Area and Zone Boundaries - concentric rings

In real-world situations, it may make more sense to establish Area/Zone boundaries along geopolitical lines, natural geographical features (e.g. along rivers or mountain ranges), or some other criteria that would not result in concentric rings.



Legend:

Figure 2.  Outbreak disease control Area and Zone boundaries - not concentric ring

Note: Figure not drawn to scale. The Vaccination Zone can be either a Protection Vaccination Zone or Containment Vaccination Zone.

Premises Classifications in Each Area / Zone

The following table shows the premises classification types associated with each area or zone.

Area/ Zone Classification Premises Classifications
Infected Zone Infected Premises
Contact Premises
Suspect Premises
At-Risk Premises
Monitored Premises
Buffer Zone Contact Premises
Suspect Premises
At-Risk Premises
Monitored Premises
Surveillance Zone Suspect Premises
Free Premises
Free Area Free Premises
Containment Vaccination Zone Suspect Premises
Vaccinated Premises
Protection Vaccination Zone Suspect Premises
Vaccinated Premises

If there is a suspect or contact premises outside of the surveillance zone, a separate control area should be created that surrounds the premises.

Guidelines for Area / Zone Dimensions and Boundaries

  • Zone immediately surrounding the Infected Premises. The IZ will initially encompass the perimeter of all presumptive or confirmed positive premises and include as many of the Contact Premises or contiguous premises as required epidemiologically or logistically. The IZ radius may be as small as 1.86 miles (3 km) radius beyond the perimeters of the presumptive or confirmed Infected Premises. The size of the IZ depends upon the FAD agent and circumstances of the outbreak. The IZ may initially be as large as a county, township, district, regional area, State, Tribal Nation, or other jurisdictional level. The boundaries of the IZ can be modified or redefined as needed by the circumstances of the outbreak.
  • Zone immediately surrounding the Infected Zone or a Contact Premises. The BZ is a scalable area with a width that is never less than the width of the IZ, but may be much larger than the IZ. The width of the BZ may be as small as 4.35 mi (7km) beyond the perimeters of the IZ. Width is generally not less than the minimum radius of the associated IZ, but may be much larger. The size of the BZ and CA depends upon the FAD agent and circumstances of the outbreak. The BZ may initially be as large as a county, township, district, regional area, State, Tribal Nation, or other jurisdictional level. The boundaries of the BZ can be modified or redefined as needed by the circumstances of the outbreak.
  • Consists of an Infected Zone and a Buffer Zone. The size of the CA depends upon FAD agent and circumstances of the outbreak. The CA radius may be as small as 6.2 miles (10 km) beyond the perimeter of the closest Infected Premises. The CA may be much larger, such as a jurisdictional unit, geographic area, or region. The size of the CA is scalable to the risk posed by the disease agent and the circumstances of the outbreak.
  • Zone established outside and along the border of the Control Area (CA), separating the Free Area (FA) from CA. Surveillance in the SZ will focus on premises determined to be at the highest risk of infection. The width of the SZ should be at least 6.2 mi (10 km). The maximum size of the SZ may be much greater.
  • The Free Area is an area not included in any CA. The FA includes a SZ but extends beyond it. The FA may also include a Protection Vaccination Zone (PVZ).    

The FA is an area in which the absence of the disease under consideration has been demonstrated by meeting requirements for “surveillance to demonstrate freedom from disease/infection” as specified in Chapter 1.4 of the OIE Terrestrial Animal Health Code 2017.

  • Emergency Vaccination Zone typically within the Control Area and may include all or part of the IZ and/or BZ. CVZ is a secondary zone designation. Quarantine and movement control requirements, surveillance requirements, and biosecurity procedures for the CA apply to the CVZ.
  • Emergency Vaccination Zone typically outside the Control Area. The PVZ will be surrounded by a SZ.

The PVZ is consistent with the (OIE) Terrestrial Animal Health Code 2017 definition for a Protection Zone. A Protection Zone is defined by the OIE as “a zone established to protect the health status of animals in a free country or free zone, from those in a country or zone of a different animal health status, using measures based on the epidemiology of the disease under consideration to prevent spread of the causative pathogenic agent into a free country or free zone. These measures may include, but are not limited to, vaccination, movement control and an intensified degree of surveillance.”

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