December 2021 USDA APHIS Veterinary Services • National Preparedness and Incident Coordination (NPIC) 1 of 3

4700 River Road Unit 42 • Riverdale, MD 20737 • (301) 851-3595

Foreign Animal Disease (FAD) Response 

Ready Reference Guide – Overview of Zones

In the Infected Zone (which is 

part of the Control Area), there 

are movement controls and surveillance activities. Infected Premises are quarantined.

In the Buffer Zone (which is part 

of the Control Area), there are 

movement controls and surveillance activities.

In the Surveillance Zone (which 

is part of the Free Area), targeted poultry surveillance may be 

conducted (i.e. commercial premises).

In the Free Area (which includes

the Surveillance Zone), routine 

or program surveillance may occur 

(i.e. NPIP and wild birds).

Zone/Area Definition

Infected Zone (IZ) Zone that immediately surrounds an Infected Premises.

Buffer Zone (BZ) Zone that immediately surrounds an Infected Zone or a Contact Premises.

Control Area (CA) Consists of an Infected Zone and a Buffer Zone.

Surveillance Zone (SZ) Zone outside and along the border of a Control Area. The Surveillance Zone is part of 

the Free Area.

Free Area (FA) Area not included in any Control Area. Includes the Surveillance Zone.

Infected Zone Buffer Zone Surveillance Zone

+ = Control Area + = Free Area
USDA APHIS Veterinary Services • National Preparedness and Incident Coordination (NPIC) 1 of 3 

4700 River Road Unit 42 • Riverdale, MD 20737 • (301) 851-3595

December 2021

Foreign Animal Disease (FAD) Response

Ready Reference Guide—Overview of Zones

In an FAD outbreak, the Incident Commander will work with the Operations 

Section and Planning Section to determine the appropriate designations. 

Infected, Contact, and Suspect Premises are subject to individual premises quarantine.

At-Risk and Monitored Premises are subject to movement control restrictions.

Summary of Premises Designations Summary of Zone and Area Designations

Example Zones, Areas, and Premises

Premises Zones and Areas

Note: Figures are not to scale.

Premises Definition Zone

Infected 

Premises (IP)

Premises where a presumptive positive case or 

confirmed positive case exists based on laboratory 

results, compatible clinical signs, case definition, 

and international standards.

Infected Zone

Contact 

Premises (CP)

Premises with susceptible animals that may have 

been exposed to the FAD, either directly or indirectly, including but not limited to exposure to animals, animal products, fomites, or people from 

Infected Premises.

Infected Zone, 

Buffer Zone

Suspect 

Premises (SP)

Premises under investigation due to the presence 

of susceptible animals reported to have clinical 

signs compatible with the FAD. This is intended to 

be a short-term premises designation.

Infected Zone, 

Buffer Zone, 

Surveillance Zone, 

Vaccination Zone

At-Risk 

Premises (ARP)

Premises that have susceptible animals, but none 

of those susceptible animals have clinical signs 

compatible with the FAD. Premises objectively 

demonstrates that it is not an Infected Premises, 

Contact Premises, or Suspect Premises. At-Risk 

Premises may seek to move susceptible animals 

or products within the Control Area by permit. Only 

At-Risk Premises are eligible to become Monitored 

Premises.

Infected Zone, 

Buffer Zone

Monitored 

Premises (MP)

Premises objectively demonstrates that it is not an 

Infected Premises, Contact Premises, or Suspect 

Premises. Only At-Risk Premises are eligible to 

become Monitored Premises. Monitored Premises 

meet a set of defined criteria in seeking to move 

su sceptible animals or products out of the Control 

Area by permit.

Infected Zone, 

Buffer Zone

Free Premises 

(FP)

Premises outside of a Control Area and not a Contact or Suspect Premises.Surveillance Zone, 

Free Area

Zone/Area Definition

Infected Zone (IZ) Zone that immediately surrounds an Infected Premises.

Buffer Zone (BZ) Zone that immediately surrounds an Infected Zone or a 

Contact Premises.

Control Area (CA) Consists of an Infected Zone and a Buffer Zone.

Surveillance Zone 

(SZ)

Zone outside and along the border of a Control Area. The 

Surveillance Zone is part of the Free Area.

Free Area (FA) Area not included in any Control Area. Includes the 

Surveillance Zone.
USDA APHIS Veterinary Services • National Preparedness and Incident Coordination (NPIC) 2 of 3 

4700 River Road Unit 42 • Riverdale, MD 20737 • (301) 851-3595

December 2021

Factors Used to Determine Control Area Size

Factors Additional Details 

Jurisdictional areas • Effectiveness and efficiency of administration

• Multi-jurisdictional considerations: local, State, Tribal, and multistate 

Physical boundaries • Areas defined by geography

• Areas defined by distance between premises 

FAD epidemiology • Reproductive rate • Modes of transmission (such as, fecal-oral, 

• Incubation period droplet, aerosol, vectors)

• Ease of transmission • Survivability in the environment

• Infectious dose • Ease of diagnosis (for example, no 

• Species susceptibility pathognomonic signs; requires diagnostic 

laboratory testing)

• Age of lesions

Infected Premises 

characteristics

• Number of contacts

• Transmission pathways and 

transmission risk  Age of animals

 Extent of animal move-  Movement of traffic and personnel to and from 

ment premises (fomite spread)

 Number of animals  Biosecurity measures in place at time of out-

 Species of animals break

Contact Premises 

characteristics

• Number and types of premises • Movement of traffic (fomites) and personnel to 

• Susceptible animal populations and from premises (fomite spread)

and population density • Biosecurity measure in place prior to outbreak

• Animal movements

Environment • Types of premises in area or • Susceptible wildlife and population density

region • Wildlife as biological or mechanical vectors

• Land use in area or region

Climate (for aerosol 

spread diseases)

• Prevailing winds

• Humidity

General area, region, or agricultural 

sector biosecurity

• Biosecurity practices in place prior to outbreak

• Biosecurity practices implemented once outbreak detected 

Number of backyard or transitional 

premises

• Types of premises, animal movements, and network of animal and fomite movements 

Continuity of business• Continuity of business plans and processe s in place or activated at beginning of outbreak (such as surveillance, negative diagnostic tests, premises biosecurity, and riskassessments)

• Permit processe s, memorandums of understanding, and information management 

systems in place or activated at beginning of outbreak 

Minimum Sizes of Zones and Areas

Note: See African Swine Fever (ASF) Zones and Areas in Feral and 

Domestic Swine for changes in the minimum sizes for zones and 

premises. 

For more information, please go to:

http://www.aphis.usda.gov/fadprep

For more details on zones and premises designations, please see 

the APHIS FAD Framework: Response Strategies (Manual 2-0).

For the Secure Poultry Supply Plan, click here

Foreign Animal Disease (FAD) Response

Ready Reference Guide—Overview of Zones

Zone or Area Minimum Size and Details

Infected Zone (IZ) Perimeter should be at least 3 km (~1.86 miles) 

beyond perimeters of presumptive or confirmed 

Infected Premises. Will depend on disease 

agent and epidemiological circumstances. This 

zone may be redefined as the outbreak continues.

Buffer Zone (BZ) Perimeter should be at least 7 km (~4.35 miles) 

beyond the perimeter of the Infected Zone. 

Width is generally not less than the minimum 

radius of the associated Infected Zone, but 

may be much larger. This zone may be redefined as the outbreak continues.

Control Area (CA) Perimeter should be at least 10 km (~6.21 

miles) beyond the perimeter of the closest 

Infected Premises. Please see the table to the 

left for factors that influence the size of the 

Control Area. This area may be redefined as 

the outbreak continues.

Surveillance Zone 

(SZ)

Width should be at least 10 km (~6.21 miles), 

but may be much larger.