Avian influenza or bird flu refers to the disease caused by infection with avian (bird) influenza (flu) Type A viruses. These viruses naturally spread among wild aquatic birds worldwide and can infect domestic poultry and other bird and animal species. Bird flu viruses do not normally infect humans. However, sporadic human infections with bird flu viruses have occurred. The links below offer more information about bird flu.
avian
The latest CDC data shows the avian flu has been detected in a range of species, including black vultures and geese. There's also a few recent reports of infection in great-horned owls, red-tailed hawks and bald eagles.
Since the avian flu began circulating last year, there have been outbreaks at poultry operations in 47 states. Outbreaks typically begin when wild birds, such as geese, infect chickens, turkeys or other waterfowl in commercial flocks or backyard flocks. Once an infection is found in any flock, the USDA euthanizes the whole flock. "This highly pathogenic disease is very deadly," says Clauer. "So the whole idea is to get on top of it and help the birds die in a humane manner and not allow the disease to continue to spread," he explains.
The virus poses a "low risk" to people, according to the CDC. The agency says avian flu viruses "usually do not infect people," though last spring, the CDC reported the infection of one person in Colorado who had been in contact with infected poultry. The person reported fatigue and was treated with an antiviral medication.
"Our stock is still down about 5%, right now," explains Emily Metz, president of the American Egg Board. But she says farmers are focused on a quick recovery and they continue to invest in prevention strategies to fend off avian flu. "I have farmers that have put in laser light systems to prevent migratory birds from landing on their barns," she explains. "I have farms that are bussing in their workers to minimize truck traffic," and lower the risk of contamination. The hope is that these efforts make the operations more resilient.
Influenza type A viruses are of most significance to public health due to their potential to cause an influenza pandemic. Influenza type A viruses are classified into subtypes according to the combinations of different virus surface proteins hemagglutinin (HA) and neuraminidase (NA). So far there are 18 different hemagglutinin subtypes and 11 different neuraminidase subtypes. Depending on the origin host, influenza A viruses can be classified as avian influenza, swine influenza, or other types of animal influenza viruses. Examples include avian influenza \"bird flu\" virus subtypes A(H5N1) and A(H9N2) or swine influenza \"swine flu\" virus subtypes A(H1N1) and A(H3N2). All of these animal influenza type A viruses are distinct from human influenza viruses and do not easily transmit among humans.\n
Aquatic birds are the primary natural reservoir for most subtypes of influenza A viruses. Most cause asymptomatic or mild infection in birds, where the range of symptoms depends on the virus properties. Viruses that cause severe disease in poultry and result in high death rates are called highly pathogenic avian influenza (HPAI). Viruses that cause mild disease in poultry are called low pathogenic avian influenza (LPAI).\n
In many patients infected by A(H5) or A(H7N9) avian influenza viruses, the disease has an aggressive clinical course. Common initial symptoms are high fever (greater than or equal to 38C) and cough followed by symptoms of lower respiratory tract involvement including dyspnoea or difficulty breathing. Upper respiratory tract symptoms such as sore throat or coryza are less common. Other symptoms such as diarrhea, vomiting, abdominal pain, bleeding from the nose or gums, encephalitis, and chest pain have also been reported in the clinical course of some patients. Complications of infection include severe pneumonia, hypoxemic respiratory failure, multi-organ dysfunction, septic shock, and secondary bacterial and fungal infections. The case fatality rate for A(H5) and A(H7N9) subtype virus infections among humans is much higher than that of seasonal influenza infections.\n
For human infections with avian influenza A(H7N7) and A(H9N2) viruses, disease is typically mild or subclinical. Only one fatal A(H7N7) human infection has been reported in the Netherlands so far. For human infections with swine influenza viruses, most cases have been mild with a few cases hospitalized and very few reports of deaths resulting from infection.\n
In terms of transmission, human infections with avian and other zoonotic influenza viruses, though rare, have been reported sporadically. Human infections are primarily acquired through direct contact with infected animals or contaminated environments, but do not result in efficient transmission of these viruses between people.\n
In 1997, human infections with the HPAI A(H5N1) virus were reported during an outbreak in poultry in Hong Kong SAR, China. Since 2003, this avian virus has spread from Asia to Europe and Africa, and has become endemic in poultry populations in some countries. Outbreaks have resulted in millions of poultry infections, several hundred human cases, and many human deaths. The outbreaks in poultry have seriously impacted livelihoods, the economy and international trade in affected countries. Other avian influenza A(H5) subtype viruses have also resulted in both outbreaks in poultry and human infections.\n
Other avian influenza viruses have resulted in sporadic human infections including the A(H7N7) and A(H9N2) viruses. Some countries have also reported sporadic human infections with swine influenza viruses, particularly the A(H1) and A(H3) subtypes.\n
Travelers to countries and people living in countries with known outbreaks of avian influenza should, if possible, avoid poultry farms, contact with animals in live poultry markets, entering areas where poultry may be slaughtered, and contact with any surfaces that appear to be contaminated with faeces from poultry or other animals. Good food safety and food hygiene practices e.g. hands washing with soap and water should be followed. Travelers returning from affected regions should report to local health services if respiratory symptoms suspecting zoonotic influenza virus infection.
Ongoing circulation of some avian influenza viruses in poultry, such as A(H5) and A(H7) viruses, are of public health concern as these viruses cause severe disease in humans and the viruses have the potential to mutate to increase transmissibility among humans. To date, although human-to-human transmission of these viruses is thought to have occurred in some instances when there had been close or prolonged contact with a patient, there has been no sustained human-to-human transmission identified.
Whether currently-circulating avian, swine and other zoonotic influenza viruses will result in a future pandemic is unknown. However, the diversity of zoonotic influenza viruses that have caused human infections is alarming and necessitates strengthened surveillance in both animal and human populations, thorough investigation of every zoonotic infection and pandemic preparedness planning.
WHO, in its capacity for providing leadership on global health matters, continuously monitors avian and other zoonotic influenza viruses closely through its Global Influenza Surveillance and Response System (GISRS). WHO, in collaboration with the World Organisation for Animal Health (OIE) and the Food and Agriculture Organization (FAO), conducts surveillance at the human-animal interface, assesses the associated risks and coordinates response to zoonotic influenza outbreaks and other threats to public health.
Influenza type A viruses are of most significance to public health due to their potential to cause an influenza pandemic. Influenza type A viruses are classified into subtypes according to the combinations of different virus surface proteins hemagglutinin (HA) and neuraminidase (NA). So far there are 18 different hemagglutinin subtypes and 11 different neuraminidase subtypes. Depending on the origin host, influenza A viruses can be classified as avian influenza, swine influenza, or other types of animal influenza viruses. Examples include avian influenza "bird flu" virus subtypes A(H5N1) and A(H9N2) or swine influenza "swine flu" virus subtypes A(H1N1) and A(H3N2). All of these animal influenza type A viruses are distinct from human influenza viruses and do not easily transmit among humans.
Aquatic birds are the primary natural reservoir for most subtypes of influenza A viruses. Most cause asymptomatic or mild infection in birds, where the range of symptoms depends on the virus properties. Viruses that cause severe disease in poultry and result in high death rates are called highly pathogenic avian influenza (HPAI). Viruses that cause mild disease in poultry are called low pathogenic avian influenza (LPAI).
In many patients infected by A(H5) or A(H7N9) avian influenza viruses, the disease has an aggressive clinical course. Common initial symptoms are high fever (greater than or equal to 38C) and cough followed by symptoms of lower respiratory tract involvement including dyspnoea or difficulty breathing. Upper respiratory tract symptoms such as sore throat or coryza are less common. Other symptoms such as diarrhea, vomiting, abdominal pain, bleeding from the nose or gums, encephalitis, and chest pain have also been reported in the clinical course of some patients. Complications of infection include severe pneumonia, hypoxemic respiratory failure, multi-organ dysfunction, septic shock, and secondary bacterial and fungal infections. The case fatality rate for A(H5) and A(H7N9) subtype virus infections among humans is much higher than that of seasonal influenza infections.
For human infections with avian influenza A(H7N7) and A(H9N2) viruses, disease is typically mild or subclinical. Only one fatal A(H7N7) human infection has been reported in the Netherlands so far. For human infections with swine influenza viruses, most cases have been mild with a few cases hospitalized and very few reports of deaths resulting from infection. 2ff7e9595c
Comments