Highly Pathogenic Avian Influenza in the US

US - This is a report via OIE on the recent outbreak of Avian Influenza in America.
calendar icon 16 February 2004
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Highly Pathogenic Avian Influenza in the US - US - This is a report via OIE on the recent outbreak of Avian Influenza in America.

See also: 18 April 2003, 14 March 2003

Emergency report

Information received on 9, 10 and 11 February 2004 from Dr Peter Fernandez, Associate Administrator, Animal and Plant Health Inspection Service (APHIS), United States Department of Agriculture (USDA), Washington, DC:

Date of the report: 11 February 2004.

Nature of diagnosis: clinical and laboratory.

Date of initial detection of animal health incident: 5 February 2004.

Estimated date of primary infection: 2 February 2004.


Location No. of outbreaks
State of Delaware, Kent County (in north-eastern United States) 1
State of Delaware, Sussex County 1

Description of affected population:

- The farm in Kent County is a non-commercial operation and functioned like a backyard flock (no biosecurity, no all-in all-out system) and had a mixture of poultry breeds of different ages. The flock consisted of about 5,000 five-week-old chickens, 4,800 white roosters and 1,200 red pullets - all in one house. Only the five-week-old chickens were clinically affected. They were separated from the rest of the birds by wire mesh, and although these older birds (the roosters and the pullets) did not appear to be clinically affected, they were directly exposed to the same agent, and therefore, presumed infected.

- The farm in Sussex County is a commercial broiler operation. All birds on the premises were approximately four-and-a-half weeks old.

Total number of animals in the outbreak:

species susceptible cases deaths destroyed* slaughtered
avi approx. 85,800 ... low mortality approx. 85,800 0

* Note by the OIE Animal Health Information Department: the number of birds mentioned in the 'destroyed' column includes the number of chickens dead from the disease.


A. Laboratory where diagnosis was made: Lasher Laboratory, University of Delaware, Georgetown, Delaware.

Further testing is being conducted at the National Veterinary Services Laboratories (NVSL) in Ames, Iowa.

B. Diagnostic tests used:

- agar gel immunodiffusion;

- enzyme immunoassay membrane test;

- real-time PCR (polymerase chain reaction).

C. Causal agent:

- Outbreak in Kent County: The specific strain of avian influenza virus detected in the affected farm has been confirmed as H7N2. All the isolates sequenced are basically identical to recent H7N2 viruses from the live-bird markets in the Northeast of the United States. The sequence at the cleavage site is PEKPKPR/GLF, a sequence that is consistent with low pathogenicity.

- Outbreak in Sussex County: The causal strain is also H7. The neuraminidase component and its pathogenicity are pending.


A. Source of agent / origin of infection: unknown at this time.

B. Other epidemiological details:

- The outbreak in Kent County (index outbreak) was detected on 5 February 2004.

- The outbreak in Sussex County was detected on 10 February. It is located about 10 km south of the outbreak in Kent County.

- Birds raised on the affected premises in Kent County were being sold specifically to supply the live bird markets in New York City.

- Poultry premises within a 3-km radius of the outbreak in Kent County have been sampled and tested. All 20 commercial farms within this radius tested negative for avian influenza.

Control measures:

- Stamping out.

- A quarantine zone has been implemented within a 3-km radius of the outbreaks.

- USDA-APHIS is working closely with the State of Delaware by conducting epidemiological investigations and area surveillance testing.

- The State of Delaware has cancelled all farmer and poultry grower related meetings, all sales and auctions of farm equipment, and all sales of live poultry.

Note by the OIE Animal Health Information Department: Only highly pathogenic avian influenza is on the OIE List A of diseases. The information in the above report seems to indicate, subject to confirmation by the biological tests currently in progress, that the virus in question is low pathogenic and unrelated to the one currently circulating in some East Asian countries.

Source: Office International des Epizooties - 13th February 2004
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