|
Outbreaks in North America with Transmission to Humans
Below is a listing of outbreaks of avian influenza in North America during which transmission to humans has occurred, or instances of human infection with avian influenza. This list will be kept current.
H7N3 in Canada
On February 19, 2004, the Canadian Food Inspection Agency announced an outbreak of avian influenza A (H7N3) in poultry in the Fraser Valley region of British Columbia. Culling operations and other measures were performed in an effort to control the spread of the virus. Health Canada reported two cases of laboratory-confirmed influenza A (H7): one in a person involved in culling operations on March 13-14, and the other in a poultry worker who had close contact with poultry on March 22-23. Both patients developed conjunctivitis (eye infection) and other flu-like symptoms; their illnesses resolved after treatment with oseltamivir.
Although these are the only laboratory-confirmed cases of avian influenza A (H7) in humans during this outbreak in Canada, 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. For more information about this outbreak, visit the Health Canada website at http://www.hc-sc.gc.ca/english/diseases/flu/avian.html or the Canadian Food Inspection Agency website at http://www.inspection.gc.ca/english/anima/heasan/disemala/avflu/situatione.shtml. H7N2 in New York
In November 2003, a patient with serious underlying medical conditions was admitted to a hospital in New York with respiratory symptoms. One of the initial laboratory tests identified an influenza A virus that was thought to be H1N1. The patient recovered and went home after a few weeks. Subsequent confirmatory tests conducted in March showed that the patient had been infected with an H7N2 avian influenza virus. An investigation to determine the source of infection is ongoing.
Outbreaks in North America Among Poultry
Below are examples of outbreaks of avian influenza among poultry. Outbreaks of these types occur from time to time and the listing below in not comprehensive or regularly updated. For more detailed and updated information about outbreaks of avian influenza in North America, visit the USDA website at http://www.aphis.usda.gov/lpa/issues/hpai_world/hpai_world.html.
H5N2 in Poultry in Texas
In February 2004, an outbreak of highly pathogenic avian influenza (HPAI) A (H5N2) was detected through routine surveillance and reported in a flock of 7,000 chickens in Gonzales County in south-central Texas. This was the first outbreak of HPAI in the United States in 20 years. Chickens from this flock were sent to two live bird markets in the Houston area. The affected flock and live bird markets were quarantined, depopulated (poultry were culled), and the premises were cleaned and disinfected. Three distinct zones, with varying intensities of surveillance, were established around the index flock for surveillance. All samples taken from the surveillance zones tested negative for avian influenza. The quarantine of the affected flock and premises was lifted on March 26. On April 1, the U.S. Department of Agriculture (USDA) informed the Office International des Epizooties (OIE) that HPAI in Gonzales County, Texas, had been completely eradicated.
The H5N2 strain in Texas was a different influenza virus from the H5N1 virus reported in parts of Asia (which also is highly pathogenic among poultry). The Texas H5N2 and the Asian H5N1 outbreaks were not related. The H5N1 outbreaks among poultry in Asia have been associated with human illness in Thailand and Vietnam, but no human illnesses occurred from the H5N2 virus in Texas.
The potential risk of human infection with an H5N2 avian virus similar to that reported in Texas is likely to be very low, but such risk does exist. Risk depends on the degree of exposure to infected birds and areas or objects contaminated by the virus and the capacity (which can vary considerably) of the virus to infect people. CDC issued interim guidance documents recommending measures to prevent possible human infection with avian influenza viruses during avian influenza outbreaks in the United States. These interim guidance documents are applicable to the Texas outbreak, as well as to other avian influenza outbreaks that may occur in the United States. These documents are available on CDC’s Web site and include Interim Recommendations for Persons with Possible Exposure to Avian Influenza During Outbreaks Among Poultry in the United States and Interim Guidance for Protection of Persons Involved in U.S. Avian Influenza Outbreak Disease Control and Eradication Activities.
H7N2 in Poultry in Maryland
In March 2004, surveillance samples from a flock of chickens in Pocomoke City, Maryland, tested positive for a low pathogenic avian influenza (LPAI) strain of H7N2. The premises were quarantined, depopulated, and cleaned and disinfected. Surveillance zones around the affected flock were established. It is likely that this is the same strain as the one that affected poultry flocks in Delaware in February 2004.
H2N2 in Pennsylvania
In February 2004, routine surveillance detected low pathogenic H2N2 in a layer flock. There was no outbreak of disease associated with this detection and no virus was isolated. The farm was put under quarantine, and 16 poultry flocks in the surrounding surveillance zone were tested for avian influenza. No other infected flocks were found.
H7N2 in Poultry in Delaware and Live Bird Markets in New Jersey
In February 2004, an outbreak of low pathogenic avian influenza A (H7N2) was reported on two chicken farms in Delaware and in four live bird markets in New Jersey that had been supplied by one of the affected Delaware farms. The affected flock and live bird markets were quarantined and depopulated, and the premises were cleaned and disinfected. In Delaware, surveillance zones were established around the affected flock. After surveillance for avian influenza found no additional cases, authorities on April 5 lifted restrictions on Delaware and eastern shore Maryland poultry farmers, allowing poultry houses to be restocked.
The H7N2 virus associated with these infections was significantly different from the H7N7 avian influenza virus that caused human illness in the Netherlands in 2003.
Although the risk of human infection with H7N2 viruses is thought to be very low, it is possible that these viruses could infect humans. CDC issued interim guidance documents to limit the possibility of human infection with avian influenza viruses during such outbreaks in the United States. These documents are available on the CDC Web site and include Interim Recommendations for Persons with Possible Exposure to Avian Influenza During Outbreaks Among Poultry in the United States and Interim Guidance for Protection of Persons Involved in U.S. Avian Influenza Outbreak Disease Control and Eradication Activities.
Professional Guidance
Interim Recommendations for Persons with Possible Exposure to Avian Influenza During Outbreaks Among Poultry in the United States
Interim Guidance for Protection of Persons Involved in U.S. Avian Influenza Outbreak Disease Control and Eradication Activities
More Information
For more information about outbreaks of avian influenza in North America, visit the USDA website at http://www.aphis.usda.gov/lpa/issues/hpai_world/hpai_world.html. |
