Interim Report: Human Infection with Avian H7 Influenza Viruses, North America
April 5, 2004

Canada
On February 19, 2004, the Canadian Food Inspection Agency announced the presence of avian influenza A (H7N3) in poultry in the Fraser Valley region of British Columbia. Culling operations have taken place on several farms in the region and are ongoing. Health Canada reported preliminary evidence that one person involved in culling operations on March 13 and 14 had developed unilateral conjunctivitis and upper respiratory symptoms on March 16. The diagnosis of influenza A (H7) was confirmed by both reverse transcription–polymerase chain reaction and cell culture of material obtained from a nasal swab. The culler was treated with oseltamivir, and all symptoms resolved. On April 2, a second laboratory-confirmed case in a poultry worker was reported by Health Canada to the World Health Organization. This person had close contact with poultry on March 22 and 23 and developed a unilateral conjunctivitis and headache on March 25. The person was treated with oseltamivir and the illness has resolved. While these are the only laboratory-confirmed cases of avian influenza A (H7) in humans during the current outbreak, approximately 10 other poultry workers exhibited conjunctival and/or upper respiratory symptoms after having contact with poultry. Use of personal protective equipment is mandatory for all persons involved in culling activities, and compliance with prescribed safety measures is being monitored. Epidemiologic, laboratory, and clinical evaluation is ongoing, as is surveillance for signs of avian influenza in exposed persons. There is currently no evidence of person-to-person transmission of avian influenza in this outbreak.

United States
The United States has experienced periodic avian influenza outbreaks during the last several decades. Evidence consistent with only one case of human infection due to avian influenza has been reported in the United States. In 2002, Virginia experienced an outbreak of avian influenza A (H7N2) in which 4.7 million turkeys and chickens were destroyed. One culler developed upper respiratory symptoms and was subsequently tested and found to have antibodies to avian influenza A (H7N2). Nasal swabs and other specimens suitable for viral isolation were not collected, and therefore virus isolation could not be undertaken. This person also may have had exposure to avian influenza through hunting activities of wild birds. However, specific serologic data are consistent with the culler being infected with H7 avian influenza during the time of the culling operation. There was no evidence of person-to-person transmission of avian influenza viruses during this outbreak, and the infected culler made a full recovery.

Human Infection with Avian Influenza H7 Viruses
Although human infection with H7 avian influenza viruses is rare, persons who have close contact with infected birds may become infected and exhibit symptoms – most commonly conjunctivitis and/or upper respiratory symptoms. For example, in 2003 the Netherlands reported cases of H7 influenza mostly among poultry workers during outbreaks of influenza A (H7N7) among poultry on several farms (http://www.cdc.gov/flu/). The risk of infection to poultry workers is low, especially when persons wear appropriate personal protective equipment and follow standard depopulation procedures when in contact with infected birds. The H7 avian influenza viruses affecting flocks in North America are distinct from the avian H5N1 viruses that have infected humans in Asia since January 2004 and have not caused the same serious symptoms and fatalities as the highly pathogenic H5N1 viruses.