Questions and answers on avian influenza - World Organisation for Animal Health
Published: March 9, 2021
Source : https://www.oie.int/en/animal-health-in-the-world/update-on-avian-influenza/questions-and-answers-on-avian-influenza/
What is avian influenza?
Avian influenza (AI) is a viral disease affecting birds, including several species of domestic poultry, as well as pet and wild birds. While AI viruses are highly species-specific, on certain occasions they have crossed the species barrier and have been isolated from mammalian species, including humans.
The many strains of AI viruses can generally be classified into two categories according to the severity of disease in poultry:
The many strains of AI viruses can generally be classified into two categories according to the severity of disease in poultry:
- Low pathogenicity AI (LPAI) that typically causes little or no clinical signs in birds; and
- Highly pathogenicity AI (HPAI) that can cause severe clinical signs and possible high mortality rates in birds.
What is the current situation of avian influenza?
Updated information on the current situation of AI is available here, based on the data reported by countries through the OIE World Animal Health Information System (OIE-WAHIS).
Since August 2020, there has been a substantial increase in the number of AI outbreaks caused by various subtypes, notably the H5N8, reported by many countries in Europe, Asia and recently in Africa, which reflect a period of heightened risks. This 2020/21 epizootic is marked by the significant involvement and mortality of wild birds. As the risk of virus introductions via migratory wild birds remains high, countries should stay vigilant, and implement effective surveillance and monitoring measures for early detection and response.
Since August 2020, there has been a substantial increase in the number of AI outbreaks caused by various subtypes, notably the H5N8, reported by many countries in Europe, Asia and recently in Africa, which reflect a period of heightened risks. This 2020/21 epizootic is marked by the significant involvement and mortality of wild birds. As the risk of virus introductions via migratory wild birds remains high, countries should stay vigilant, and implement effective surveillance and monitoring measures for early detection and response.
What are the causes of the current wave of avian influenza cases and is it worse than in previous years?
Molecular characterization of the currently circulating AI virus subtypes shows genetic variability from previous years. This might be explained by multiple reassortments with low pathogenic viruses circulating in wild birds. The evolution of the viruses and these recent events need to be closely monitored and further studied in order to assess the risks.
It is most likely that migratory wild birds, followed by local farming practices, have contributed to the dissemination and introduction of the virus into new countries and farms. A similar situation of H5N8 epizootics in many countries associated with wild bird migration occurred in 2016/17.
The H5N8 virus has also reassorted with other wild bird influenza viruses to form new subtypes, which were also reported by countries.
It is most likely that migratory wild birds, followed by local farming practices, have contributed to the dissemination and introduction of the virus into new countries and farms. A similar situation of H5N8 epizootics in many countries associated with wild bird migration occurred in 2016/17.
The H5N8 virus has also reassorted with other wild bird influenza viruses to form new subtypes, which were also reported by countries.
What factors can facilitate the spread of avian influenza?
The dynamic of the spread of influenza viruses is extremely complex and difficult to predict. Several factors can influence it, such as the wild bird migration pattern, unregulated trade, farming systems, biosecurity and immunity status.
During the Northern Hemisphere winter, the wild bird movements may increase, and lower temperatures may facilitate the environmental survival of AI viruses, increasing exposure of infection in poultry. Additionally, the mixing of wild birds from different geographic origins during migration can increase the risk of virus spread and genetic reassortment resulting in changes in viral properties.
At local level, as the AI viruses can survive for long periods in the environment, they can be easily transmitted from farm to farm by the movement of infected animals, as well as contaminated boots, vehicles and equipment if the adequate biosecurity measures are not implemented.
During the Northern Hemisphere winter, the wild bird movements may increase, and lower temperatures may facilitate the environmental survival of AI viruses, increasing exposure of infection in poultry. Additionally, the mixing of wild birds from different geographic origins during migration can increase the risk of virus spread and genetic reassortment resulting in changes in viral properties.
At local level, as the AI viruses can survive for long periods in the environment, they can be easily transmitted from farm to farm by the movement of infected animals, as well as contaminated boots, vehicles and equipment if the adequate biosecurity measures are not implemented.
Has the COVID-19 pandemic hindered the implementation of the preventive measures for avian influenza?
Sustaining veterinary activities amid the COVID-19 pandemic is essential to avoid the detrimental impacts of animal diseases, which could exacerbate the current sanitary and socio-economic crises.
Despite the challenging context, Veterinary Authorities in the affected countries have responded to contain AI outbreaks in poultry with stamping out measures, heightened surveillance, and recommendations to poultry owners to increase biosecurity.
Despite the challenging context, Veterinary Authorities in the affected countries have responded to contain AI outbreaks in poultry with stamping out measures, heightened surveillance, and recommendations to poultry owners to increase biosecurity.
What is the impact of avian influenza?
AI poses a major threat to animal health and welfare and can lead to devastating consequences at different levels of society.
The disease severely affects the livelihoods of small and large-scale poultry producers and many other actors involved in the supply chain. Farmers might experience a high level of mortality in their flocks, and therefore job losses can also be significant.
Additionally, to contain outbreaks and control the disease, contact and suspected bird populations often need to be culled, threatening food security worldwide.
The presence of HPAI also restricts international trade in live birds and poultry meat, heavily impacting national economies.
The disease severely affects the livelihoods of small and large-scale poultry producers and many other actors involved in the supply chain. Farmers might experience a high level of mortality in their flocks, and therefore job losses can also be significant.
Additionally, to contain outbreaks and control the disease, contact and suspected bird populations often need to be culled, threatening food security worldwide.
The presence of HPAI also restricts international trade in live birds and poultry meat, heavily impacting national economies.
What is the risk of avian influenza for human health?
The epidemiology of AI viruses is complex: They can change and evolve by mutation and reassortment, with the emergence of new subtypes causing significant impacts on animal health and production. Some subtypes - not all - can be zoonotic and therefore pose a threat to human health.
Transmission of AI viruses to humans occurs when there is close contact with infected birds or heavily contaminated environments.
In February 2021, human cases of AI subtype H5N8 were reported by Russian authorities to the World Health Organization (WHO). The OIE/FAO network of experts on animal influenza (OFFLU) analysed the preliminary information of the event and stated that, to date, there is no evidence to suggest that severe human infections or human-to-human transmission of this virus have occurred. This situation likely represents an isolated spillover event of the virus as genetic evidence suggests that these viruses were derived from chickens with no adaptation to humans.
More information is available on the OFFLU statement (February 2021).
Transmission of AI viruses to humans occurs when there is close contact with infected birds or heavily contaminated environments.
In February 2021, human cases of AI subtype H5N8 were reported by Russian authorities to the World Health Organization (WHO). The OIE/FAO network of experts on animal influenza (OFFLU) analysed the preliminary information of the event and stated that, to date, there is no evidence to suggest that severe human infections or human-to-human transmission of this virus have occurred. This situation likely represents an isolated spillover event of the virus as genetic evidence suggests that these viruses were derived from chickens with no adaptation to humans.
More information is available on the OFFLU statement (February 2021).
What are the food safety recommendations?
There is no evidence to suggest that the consumption of poultry meat or eggs could transmit the AI virus to humans. However, as a general precautionary measure, animals that have been culled as a result of the implementation of control measures in response to an AI outbreak, including the H5N8 subtype, should not enter the human food and animal feed chain.
What are the key elements to prevent the further spread of avian influenza?
Controlling avian influenza at its animal source is essential to decrease the risk and, consequently, the impact of the disease.
In this context, continued surveillance of avian influenza virus in wild birds and poultry combined with timely generation and dissemination of data are crucial. This early warning system enables the international community to follow the virus evolution and to promptly detect changes in the virus properties, such as introductions, reassortments or genetic mutations, that are relevant for animal and public health.
When cases are detected in animals, control measures should be implemented at the level of the infected farm and within a short radius around the infected premises, in an effort to rapidly contain and eradicate the disease.
More information on these measures is available on the OIE Terrestrial Animal Health Code - Infection with avian influenza viruses.
In this context, continued surveillance of avian influenza virus in wild birds and poultry combined with timely generation and dissemination of data are crucial. This early warning system enables the international community to follow the virus evolution and to promptly detect changes in the virus properties, such as introductions, reassortments or genetic mutations, that are relevant for animal and public health.
When cases are detected in animals, control measures should be implemented at the level of the infected farm and within a short radius around the infected premises, in an effort to rapidly contain and eradicate the disease.
More information on these measures is available on the OIE Terrestrial Animal Health Code - Infection with avian influenza viruses.
What prevention measures are recommended at farm level?
It is essential for poultry farmers to maintain biosecurity practices to prevent the introduction of the virus. Some of these measures include:
- Prevent contact between poultry and wild birds
- Minimise movements around poultry enclosures
- Maintain strict control over access to flocks by vehicles, people and equipment
- Clean and disinfect animal housing and equipment
- Avoid the introduction of birds of unknown disease status
- Report any suspicious case (dead or alive) to the veterinary authorities
- Ensure appropriate disposal of manure, litter and dead animals
- Vaccinate animals, where appropriate
What is the World Organisation for Animal Health (OIE) doing to tackle avian influenza?
As the leading world organisation on animal health, the OIE works with its OFFLU network of experts on animal influenzas, as well as with its partners, notably the World Health Organization (WHO) and Food and Agriculture Organization (FAO), to assess the risks of AI viruses and provide the needed guidance and recommendations.
To support countries in the fight against this disease, the OIE developed international Standards on AI, which provide the framework for the implementation of effective surveillance and control measures. These standards follow a responsive, science-based and transparent process (more about the OIE standard-setting process) and are published in the OIE Terrestrial Animal Health Code, after being adopted by our Member Countries.
Additionally, the OIE World Animal Health Information System (OIE-WAHIS) provides a window on the disease situation worldwide. Through its online platform and a mobile application, the system disseminates information about AI outbreaks and sends alerts on events in real time. This allows the international community to follow the evolution of the virus and, therefore, to implement appropriate and timely responses.
To support countries in the fight against this disease, the OIE developed international Standards on AI, which provide the framework for the implementation of effective surveillance and control measures. These standards follow a responsive, science-based and transparent process (more about the OIE standard-setting process) and are published in the OIE Terrestrial Animal Health Code, after being adopted by our Member Countries.
Additionally, the OIE World Animal Health Information System (OIE-WAHIS) provides a window on the disease situation worldwide. Through its online platform and a mobile application, the system disseminates information about AI outbreaks and sends alerts on events in real time. This allows the international community to follow the evolution of the virus and, therefore, to implement appropriate and timely responses.
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