Avian influenza is a viral disease, which occurs primarily in birds. Avian influenza viruses are either high or low pathogenic viruses (HPAI and LPAI, respectively) depending on their ability to cause severe or mild disease and mortality in chickens. This is reflected also in the molecular characteristic of the virus.
Wild birds, in particular aquatic birds, are natural hosts and reservoirs for all types of avian influenza viruses, so they play a major role in the evolution, maintenance and spread of these viruses.
Poultry infected with LPAI may show mild signs of the disease or none at all. Infections caused by HPAI can cause severe disease and death in poultry.
The occurrence of avian influenza viruses in the European Union is associated mainly with their introduction via migratory wild birds such as wigeons or Barnacle geese.
The infection with avian influenza viruses in wild birds is seasonal, with the highest rate of infection being in juvenile birds, in the autumn. Wild birds carry avian influenza viruses over long distances along their migration flyways and shed those viruses in the faeces and respiratory secretions contaminating the environment.
During the winter, with the movements of wild birds increasing and the lower temperatures facilitating the environmental survival of avian influenza viruses, exposure of infection in poultry is on the rise.
>Additionally, the mixing of wild birds from different geographic origins during migration can increase the risk of virus spread and reassortment resulting in changes in viral properties.
Moreover, indirect contact with contaminated farm equipment can also contribute to the infection of poultry.
The European Food Safety Agency (EFSA) identified four major entry pathways for avian influenza viruses via wild birds into the EU. These are:
i. The northeast area (NE), defined as the border between EU and Russia from the north of Finland until north of Ukraine. In this area, migratory wild birds generally enter the EU during the autumn migration (and to a limited extend during cold spells in winter), via incoming birds from breeding areas in the taiga and tundra zones in Russia.
ii. The east area (E), defined as the EU border from Ukraine to Cyprus. In this area, migratory wild birds generally enter during the autumn migration from breeding areas east of the EU, including the connectivity with the Black Sea and the Caspian Sea. In times of cold spells, migration can also occur later in winter season.
iii. The south area (S), defined as the EU border from southern Portugal to Cyprus, across which migratory wild birds generally enter the EU in spring on return migration from non-breeding areas predominantly located in sub-Saharan Africa.
iv. The northwest area (NW), defined as the British Isles. In this area, migratory wild birds may enter the EU in autumn via migratory birds from breeding areas in Iceland and Greenland (and even from Canada). Compared to the other entry pathways, this route holds a quantitatively minor proportion of all wild bird entries.
Infection with avian influenza viruses is a major concern due to the economic consequences following infection and disease in poultry and also due to their volatile genetic characteristic, which may increase their ability to change and evolve by mutation and mixing with other avian influenza viruses. These factors may cause the emergence in new subtypes with increased pathogenicity or potential to infect other species of animals and humans.
The economic consequences following infection of poultry with HPAI are related to important production losses in infected farms, to the implementation of eradication measures and the trade disruptions in the affected area where movement restrictions for poultry and poultry products are in place as measures for prevention and control of the disease.
The international trade with poultry and poultry products has to comply with the standards of the World Organization for Animal Health (OIE standards) for infection with high pathogenicity avian influenza viruses. The presence of HPAI in poultry restricts international trade in live birds and poultry meat, having serious impact on national economies.
Infection of poultry with LPAI also have some consequences for the affected farms. Besides the loss in the production, which may also occur following infection with LPAI, movement of poultry within the EU from an infected farm is restricted for the following 21 days after confirmation of infection. Moreover, in very few cases, it could be proven that HPAI outbreaks were caused by intrinsic mutation of LPAI virus to HPAI virus.
Avian influenza occurs worldwide, with different strains more prevalent in certain areas of the world. Some of the avian influenza viruses are circulating in poultry in Asia while others have spread globally through wild bird migrations.
Reports of the Avian Influenza situation in the world can be found on the OIE dedicated webpage.
Information on the situation with HPAI in the EU can be found here .
Most strains of avian influenza virus are relatively harmless to their natural wild bird hosts and do not infect humans.
Although most of the avian influenza viruses are primordially infecting only birds, some variants may develop mutations that increase their potential to infect also other species like mammals, including humans.
People who are in close contact with infected birds are at risk of being infected with avian influenza viruses. They should wear personal protective equipment (PPE) and avoid unprotected direct contact with sick or dead birds, carcasses, faeces as well as potentially contaminated environments.
While most human cases are limited to conjunctivitis or mild respiratory symptomes, some viruses may cause severe illness in some individuals.
More information related on risks for public health of avian influenza viruses can be found on the webpage of European Center for Disease Prevention and Control (ECDC) dedicated to avian influenza.
Bio-security measures at farm are the first line of protection against the introduction and spread of avian influenza viruses for poultry or captive birds.
The European Food Safety Authority (EFSA) adopted in 2017 a comprehensive scientific opinion on avian influenza, confirming that the strict implementation of biosecurity measures plays a key role in preventing the spread of HPAI viruses from wild birds to poultry and other captive birds. As a non-exhaustive list of biosecurity measures generally valid for all type of poultry or captive birds establishments, the following can be mentioned:
- restrict wild birds access to contact poultry,
- ponds or other water surfaces with open access for wild birds need to be avoided on the poultry premises,
- confine, and at least limit the outdoor access area of domestic birds in high-risk periods,
- use hygiene locks and restrict access of people to poultry houses. Limit contacts with other poultry holdings (fomite, material, machinery, feed, workers),
- if poultry cannot be confined during high-risk periods, it is recommended to prevent direct contact between wild birds and poultry by reducing the size of the outdoor area and/or by using netting or verandas. Feed and water should be provided under a roof or a horizontal fabric.
Vaccination against avian influenza may be applied under specific conditions. Vaccination to prevent the transmission of HPAI virus may be part of a disease control programme.
In accordance with the OIE standards, vaccination will not affect the high pathogenicity avian influenza status of a free country or zone if sufficient surveillance support the absence of the infection with field virus.
According to EU legislation for animal health, HPAI is a Category A disease for which immediate eradication measures must be taken as soon as it is detected.
Following confirmation of HPAI virus in an establishment with poultry or captive birds, the national competent authorities immediately take stamping out measures in the affected establishment: killing of all birds, safe disposal of carcasses, products or other potentially contaminated materials, cleaning and disinfection. Similar measures may need to be applied in the epidemiologically linked establishments and also preventive killing may be applied under certain circumstances.
In addition, a restricted zone is established at least 10 km around the affected establishment where specific control measures are applied to establishments where birds are kept, to assess the disease situation and control the spread (e.g. inventory, visits by official veterinarians, clinical and laboratory surveillance, movement restrictions of birds and their products, etc.). Those measures are maintained in the restricted zone for minimum 30 days after eradication of the HPAI virus in the infected establishment.
Moreover, in order to prevent any unnecessary disturbance of trade within the Union, and to avoid unjustified barriers to trade being imposed by third countries, the Commission include those restricted zones in the EU zoning for HPAI. The EU zoning (separating disease free zones from those with infection) is published in the Official Journal of the EU as emergency measures in relation to outbreaks of highly pathogenic avian influenza in certain Member States.
The map with the geographical distribution of the HPAI detections in wild birds and poultry establishments in the current HPAI epidemic season can be found here.
A detailed overview on the evolution of the HPAI situation in Member States since the start of the current HPAI epidemic season and the adopted emergency measures can be found in the Chronology of events.
The placing on the market and use of veterinary medicinal products in the EU, including vaccines is regulated by the EU legislation on veterinary medicinal products (VMP Regulation).
According to the VMP Regulation a veterinary medicinal product may be placed on the market and used in EU Member States if it has been authorised by the European Medicine Agency (EMA) or by the competent authorities in the Member States.
If indicated by the epidemiological situation and the particular circumstances in the area where there is a risk of spread of HPAI viruses to poultry, vaccination against highly pathogenic avian influenza may be used as part of the official measures put in place by the competent authorities of the EU Member States for prevention and control of the disease and based on the specific rules provided by the relevant EU legislation.
At present, there is one vaccine against avian influenza that has a marketing authorisation from EMA and can therefore be used in the European Union.
At the request of the Commission, a number of scientific opinions and reports in relation to avian influenza have been published by EFSA since 2005, assessing different risks.
2015-2016 and 2016_2017 epidemic seasons of HPAI in the EU were characterised by high numbers of infected wild birds, different avian influenza virus subtypes involved, and the large geographical extension of the epidemic not only in the Union but also in Asia and Africa. Consequently, the Commission asked EFSA to closely follow the development of the epidemiological situation for avian influenza within the EU and worldwide, in particular with a view to describe the evolution of virus spread from certain regions towards the EU.
EFSA was therefore asked by the Commission to issue quarterly reports with update on the avian influenza situation with particular attention to the possible impact of the circulating avian influenza viruses. For the purpose of these quarterly reports, considering the probability for the AI viruses to develop zoonotic potential, EFSA was asked to collaborate with European Union Reference Laboratory for Avian Influenza and with ECDC.
In addition, the results of the surveillance carried out by the EU Member States are collected and assessed by EFSA, based on the request from the Commission. Scientific reports with the results of this assessments are also published by EFSA on annual basis.
The risk of transmission of avian influenza viruses from wild birds to the general public is low. Most cases of human infection with avian influenza viruses involved very close direct contact with sick poultry.
In order to minimise any risk of getting infected with avian influenza viruses from wild birds, people should avoid touching sick or dead wild birds with bare hands.
People that are involved in the eradication of HPAI outbreaks should use appropriate personal protective equipment.
The latest information on the monitoring and options for public health measures can be found in the last quarterly report of EFSA.
Yes, poultry and poultry products put on the market in the EU can be prepared and consumed as usual, following good hygienic practices and proper cooking.
Although avian influenza typically affects birds, animals of mammalian species, including pigs, seals, wild boars, foxes, have been found infected, in few cases, with avian influenza viruses.