: Avian influenza

April 13, 2006

Background
Avian influenza has appeared from time to time in regions all over the world, including in the United States. Avian influenza spreads easily among wild birds, but can also infect domesticated birds, including chickens, turkeys, ducks, and pet birds; humans; and a variety of other mammals. Highly pathogenic avian influenza can devastate entire flocks of poultry.

The American Veterinary Medical Association is coordinating with other veterinary associations, CDC, USDA, and other partners domestically and internationally on this issue to obtain and provide accurate information and will disseminate additional information to health professionals and the public as it becomes available.

Q:
What is avian influenza?

A:
Avian influenza (AI) is a viral disease that most commonly affects birds. There are many subtypes of influenza viruses — variants and strains may affect birds, other animals and humans. Influenza viruses are classified based on the relative numbers of hemaglutinin (H) and neuraminidase (N) antigens they have on their surfaces. Avian influenza is further defined by whether it is of high pathogenicity or low pathogenicity. The influenza virus affecting poultry flocks and other birds in Asia, Europe, the Middle East, and Africa during recent months is H5N1 highly pathogenic avian influenza (HPAI). This particular form of AI is deadly to poultry, and some wild birds, and can spread rapidly among an entire flock of birds. To date, H5N1 HPAI has not been identified in birds in the United States or in North America. Low pathogenic AI causes either no disease or mild disease in poultry and some wild birds. Avian influenza is uncommon in most commercial poultry flocks; it is most often identified in poultry raised outdoors.


Q:
How is avian influenza transmitted?

A:
Avian influenza is most often spread via direct contact between healthy birds and infected birds, and may be spread indirectly through contact with contaminated equipment and materials. The virus is found in secretions from the nares, mouth, and eyes of infected birds and is also excreted in their feces. Contact with contaminated fecal material is the most common means of bird-to-bird transmission, although airborne secretions are another major means of transmission within poultry houses. Wild ducks can introduce low pathogenic AI into domestic flocks raised on range or in open flight pens via fecal contamination.

Spread of AI between poultry facilities almost always follows the movement of contaminated people and equipment. Avian influenza virus also can be isolated from the outer surfaces of egg shells. Transfer of eggs, therefore, is a potential means of AI transmission. Airborne transmission of virus from farm to farm is highly unlikely.

HPAI can be spread from birds to people as a result of extensive direct contact with infected birds, such as defeathering during home slaughter of poultry. Concerns about public health relate to the potential for the virus to mutate into a form that could easily spread from person to person.


Q:
Can people become ill with avian influenza?

A:
Yes. Fortunately, however, transmission of H5N1 AI to humans is rare. The virus is found in the droppings, nasal secretions, and saliva of infected birds. Bird-to-human transmission most commonly occurs when particles from contaminated feces are inhaled. Although human-to-human transmission is theoretically possible, so far, there are only a few cases where human-to-human transmission is thought to have occurred. And in those cases, human-to-human transmission did not continue beyond the immediate contacts of the primary case.


Q:
How do humans become infected?

A:
Inhalation and contamination of mucous membranes such as eyelids (via contaminated hands) are the most common routes of infection for humans. Currently, the risk of contracting AI for anyone who does not have close contact with infected poultry is quite low.


Q:
Can you catch avian influenza by eating chicken, turkey, duck or even eggs?

A:
According to the US Department of Agriculture (USDA), proper handling and cooking of meat and eggs provides protection against contracting avian influenza and other viruses, as well as bacteria such as Salmonella and E coli. These organisms are readily killed by adequate cooking. USDA strongly recommends consumers follow safe food handling and preparation techniques every day. Visit [عزيزي الزائر يتوجب عليك التسجيل للمشاهدة الرابطللتسجيل اضغط هنا] for food safety instructions.


Q:
Is it true that cats can get avian influenza?

A:
Although not usually susceptible to influenza type-A infections, results of a research study published in September 2004 demonstrated that domestic cats can become infected with the H5N1 virus and are capable of transmitting the virus to other cats. In February 2006, authorities in Germany reported that a domestic cat had died from H5N1 avian influenza. That cat lived in the northern island of Ruegen, where more than 100 wild birds are believed to have died of the disease, and it likely contracted the disease by consuming one of those infected birds. In March 2006, three cats in Austria were confirmed to be ill with the H5N1 virus. The latter cats were among 170 living in an animal shelter where the disease had been detected in chickens a month earlier. Prior to confirmation of these naturally occurring feline cases, there had been anecdotal reports of H5N1 infection in domestic cats in southeast Asia and Iraq.

Large cats kept in captivity have been diagnosed with avian influenza as well. In December 2003, two tigers and two leopards that were fed fresh chicken carcasses from a local slaughterhouse died at a zoo in Thailand. An investigation identified H5N1 in tissue samples. In February and March 2004, the virus was detected in a clouded leopard and white tiger, respectively, both of which died in a zoo near Bangkok. In October 2004, 147 of 441 captive tigers in a zoo in Thailand died or were euthanatized as a result of infection after being fed raw chicken carcasses. Results of a subsequent investigation suggested that at least some tiger-to-tiger transmission occurred in that facility.


Q:
How do cats become infected? Can they spread the virus?

A:
All natural H5N1 infections in domestic cats reported to date appear to have been associated with outbreaks in domestic or wild birds and acquired through ingestion of raw infected meat. Fortunately, there is no evidence to date that domestic cats play a role in the natural transmission cycle of H5N1 viruses. No cases of avian influenza in humans have been linked to exposure to sick cats and no outbreaks among populations of domestic cats have been reported. Cats in a laboratory/research setting have been shown to be able to spread the virus to other cats, but it is not known whether such spread occurs under natural conditions.


Q:
What is the current risk that a cat will become infected with avian influenza A (H5N1) in the United States?

A:
The strain of H5N1 circulating in Asia, the Middle East, Africa and Europe has not yet been identified in the United States, so the risk of a cat contracting the disease in this country is currently very low. Although the risk of feline infection is also low in Europe, increases in the number of wild birds affected and the death of the cat in Germany have caused the European Centre for Disease Prevention and Control to issue preliminary recommendations for cat owners living in H5N1-affected areas. These include keeping domestic cats indoors to prevent exposure to potentially infected birds, avoiding contact with semi-domestic and feral cats living outside the home, and refraining from feeding raw poultry to cats. They have also encouraged owners of ill cats, particularly those known to have been exposed to sick or dead birds, to have their cats examined by a veterinarian.


Q:
Can dogs become infected with avian influenza?

A:
Like cats, dogs are not usually susceptible to avian influenza viruses; however, an unpublished study carried out in 2005 by the National Institute of Animal Health in Bangkok indicated that dogs could be infected with the virus, but no associated disease was detected. This limited information is insufficient to conclude definitively whether dogs are susceptible to the virus.


Q:
How do dogs become infected? Can they spread the virus?

A:
There is not enough information available about avian influenza H5N1 infection in dogs to know how infection would occur. Affected domestic cats in Europe appear to have become infected by feeding upon infected poultry or wild birds. If dogs are susceptible to avian influenza A (H5N1), infection may be by the same route.


Q:
What is the current risk that a dog will become infected with avian influenza virus H5N1 in the United States?

A:
At the moment, there is little risk of a dog in the United States becoming infected with avian influenza A (H5N1) because the virus circulating in Asia, Europe, the Middle East and Africa has not yet entered the United States.


Q:
What other species can get avian influenza?

A:
In addition to wild and domestic birds and poultry, humans, cats, and dogs, we know that pigs, palm civets, cynomolgus macaques, New Zealand white rabbits, stone martens, tigers, leopards, ferrets and rats can become infected with the H5N1 avian influenza virus. The avian influenza A (H5N1) virus that emerged in Asia in 2003-2004 is evolving and it's possible that other mammals may be susceptible to infection as well.


Q:
What's being done to stop avian influenza from spreading?

A:
In countries where avian influenza is prevalent, infected poultry are destroyed to reduce the risk of infecting other birds and to minimize human exposure. Awareness has been heightened and related education has become a priority in affected areas around the world. USDA recognizes the potential threat to human health and has therefore increased its surveillance and control efforts to detect and, if needed, contain and eradicate AI. More information about USDA's efforts and response to AI in the United States is available at [عزيزي الزائر يتوجب عليك التسجيل للمشاهدة الرابطللتسجيل اضغط هنا] and [عزيزي الزائر يتوجب عليك التسجيل للمشاهدة الرابطللتسجيل اضغط هنا]. In 2006, the US commercial chicken industry started a voluntary program to test each flock on the farm before it is sent to slaughter. Any flock found to have AI in the H5 or H7 types will be humanely euthanatized and disposed of in a safe, environmentally responsible manner. Also in 2006, surveillance for possible infection in wild birds in the United States was greatly increased.


Q:
Is it risky to travel to areas presently affected by avian influenza?

A:
When traveling to any foreign country, especially areas affected by avian influenza, it is always wise to check with international travel authorities or the CDC for updated information. Visit [عزيزي الزائر يتوجب عليك التسجيل للمشاهدة الرابطللتسجيل اضغط هنا].