- Q1. What is zoonotic influenza ?
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Zoonotic influenza is an infectious disease caused by the enveloped RNA virus, influenza type A. Influenza type A viruses are widespread within many different avian and mammalian host species. Influenza viruses are species-specific, yet occasionally, transmission from one species to another species or to humans can occur (figure 1).
Humans can be infected sporadically with novel influenza A viruses of animal origin (zoonotic influenza), such as avian influenza A virus (AIV) subtypes A(H5N1), A(H5N6), A(H7N9), A(H7N7) and A(H9N2), and swine influenza A virus subtypes H1N1, H1N2 and H3N2[1].
The risk of a large-scale epidemic by a new or emerging influenza A virus is higher if there are more spill-over events from an animal influenza virus to humans or by reassortment between avian, swine and seasonal human or other mammalian influenza viruses (EFSA and ECDC, 2024). Human-adaptative mutations may be acquired via reassortment between human and animal influenza viruses without the need for a gradual adaptation like via point mutations; this risk is highest in mammalian hosts that harbour mammalian-adapted influenza viruses (primarily humans and pigs, but also mustelids and foxes).
Figure 1: Schematic diagram showing the host range of influenza A viruses. Reservoirs and interspecies transmission events of influenza A viruses and the subtypes involved in these events. Aquatic wild birds represent the natural reservoir of influenza A viruses, from which they can be transmitted to a variety of other hosts. Circled arrows represent continuous virus circulation among wild birds, domestic birds, domestic animals, bats, horses, pigs and humans.
Source: AbuBakar, U.; Amrani, L.; Kamarulzaman, F.A.; Karsani, S.A.; Hassandarvish, P.; Khairat, J.E. Avian Influenza Virus Tropism in Humans. Viruses 2023, 15, 833. https:// doi.org/10.3390/v15040833
[1]Sporadic human infections with influenza viruses that circulate in swine and not humans have occurred. When this happens, these viruses are called “variant viruses.” They also can be denoted by adding the letter “v” to the end of the virus subtype designation. Human infections with H1N1v, H3N2v and H1N2v viruses have been detected worldwide.
- Q2. How can zoonotic influenza infections be prevented?
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As a general precaution, it is recommended to avoid any contact with dead or sick birds, mustelids or foxes. If contact is unavoidable, appropriate personal protective equipment (PPE) must be used. Special care should be taken to avoid contact with mucous membranes such as the mouth, nose and eyes. Always wear disposable gloves and a face mask, and follow proper hygiene measures when handling carcasses and sick animals.
When entering the premises of a poultry or swine farm, the biosecurity measures and PPE must be applied by visitors, especially when entering the barns or technical areas. These preventive measures are regularly updated by the FAVV/AFSCA.
Recommended guidelines:
- Q3. Can zoonotic influenza be transmitted through food?
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Properly cooked poultry meat and eggs do not pose a risk of avian influenza infection. However, as a general precautionary measure, animals that are sick or have been culled as a result of the implementation of control measures in response to an avian influenza outbreak and their products are not allowed to enter the human food and animal feed chain
Likewise, poultry vaccinated against avian influenza and their eggs can be safely consumed. The withdrawal period of the current vaccines is zero days, which means that the vaccines do not contain any ingredients that are likely to pose a risk for consumers of vaccinated birds[1]. It is worth noting, however, that vaccination of poultry against avian influenza is not currently permitted in Belgium.
Source: https://favv-afsca.be/sites/default/files/2025-06/Zoonotic-risk-of-avian-influenza_NL_V14.pdf
With regard to animal feed, such as cat food made from poultry meat, raw meat, particularly raw poultry should be avoided, as it may be contaminated with Highly Pathogenic Avian Influenza Viruses (HPAI) or other pathogens. Fully cooked meat, however, remains safe.
Source: https://favv-afsca.be/sites/default/files/2025-06/risk-raw-meat-based-pe… - Q4. What is the risk of human-to-human transmission ?
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Sporadic human cases of animal influenza have previously been reported worldwide. Transmission of animal influenza viruses to humans remains rare, and no sustained human-to-human transmission has been observed to date. According to the last European Centre for Disease and Control (ECDC) surveillance report (June 2025), the overall risk of zoonotic influenza transmission to the general public in EU/EEA countries is considered low, while the risk for occupationally exposed individuals (refer Q.8) is assessed as low to moderate.
- Q5. How is zoonotic influenza monitored in Belgium?
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The Highly Pathogenic Avian Influenza (HPAI) surveillance programme in poultry farms and wild birds, provides the basis for the year-round early warning system. It is coordinated at central level by Federal Agency for the Safety of the Food Chain (FASFC). This programme includes active surveillance in selected commercial and non-commercial poultry establishments and mainly passive surveillance in wild birds and poultry establishments.
Information on the HPAI epidemiological situation can be found here
Regarding zoonotic influenza surveillance in humans, the NRC respiratory pathogens (Sciensano) in collaboration with the Avian Virology and Immunology, and with the Flemish and Walloon Regional Health Authorities is implementing a research project aiming at active surveillance of zoonotic transmission events in exposed populations (ZOOIS).
Additionally, the SARI (Severe Acute Respiratory Infections) surveillance program in Belgium monitors the number of new acute respiratory infections in nine hospitals on a weekly basis throughout the year. This surveillance program could be considered as passive surveillance, as each positive sample of influenza A is typed and subtyped for, among others, detection of zoonotic influenza.
- Q6. What is the incubation period and infectious period for zoonotic influenza ?
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At present, the information available on the incubation period of animal influenza virus infection in humans is very limited and infections from viruses of older clades might be different[1].
Based on the limited available evidence from human cases, the incubation period of A(H5N1) infection is estimated to be up to 7-9 days, usually 3−5 days after last known exposure[2]. The infectious period can start 1−2 days before symptom onset and usually lasts up to one week after symptom onset[3]. However, this can vary considerably depending on a number of factors including the person’s individual’s overall health, age and immune response.
[1]: European Centre for Disease Prevention and Control. Investigation protocol for human exposures and cases of avian influenza in the EU/EEA. Stockholm: ECDC; 2023.
- Q7. Is there a vaccine available for zoonotic influenza?
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Some vaccines against zoonotic influenza are available on the EU market. The zoonotic influenza vaccine Seqirus containing the strain H5N8 (clade 2.3.4.4b), is currently considered to be the best candidate to provide protection against circulating H5 influenza A strains[1]. In Belgium, routine vaccination against avian influenza is not recommended for the general population, neither for individuals considered to be in high-risk groups.
Vaccination against seasonal influenza can help reduce the risk of reassortment between human and animal influenza viruses. Reduction of severity of A(H5N1) illness has not be proven. Recent studies do not prove that existing immunity following seasonal influenza vaccination or natural infection would protect the population against A(H5N1).[2]
For further details or updates on seasonal influenza vaccination, including for at-risk populations, consult the Superior Health Council recommendations.
[1]: EMA/12219½024 https://www.ema.europa.eu/en/documents/overview/zoonotic-influenza-vaccine-seqirus-epar-medicine-overview_en.pdf
[2]: Stevenson-Leggett P, et al. Investigation of Influenza A(H5N1) Virus Neutralization by Quadrivalent Seasonal Vaccines, United Kingdom, 2021-2024. Emerg Infect Dis. 2025 Jun;31(6):1202-1206. doi: 10.3201/eid3106.241796. PMID: 40439507; PMCID: PMC12123933.
- Q8. Which groups are at increased risk of exposure ?
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High-risk groups include[1] individuals who have direct or indirect contact with an infected animal, their secretions or their environment (e.g. dust) without following the appropriate technical and organizational protective measures. This group includes individuals who are:
Exposed to animals[2] and their environment, including
- Farmers, especially those raising chickens, pigs or mustelids, including their families residing in farms
- Veterinarians and other professionals with occupational exposure to infected animals
- Individuals involved in cleaning contaminated areas following culling operations or exposed to animal faeces or secretions, particularly during clean-up, waste disposal, or in backyard settings with poor biosafety and biosecurity measures
- Hunters, volunteers, or staff who handle wild animals or their carcasses
- Forestry workers who may come into contact with sick or dead animals
- Meat processing industry workers, especially those handling live or recently slaughtered animals
Exposed to isolated virus and positive specimens, including
- Laboratory personnel handling specimens that test positive for zoonotic influenza viruses
- Public health professionals, inspectors (e.g. AFSCA), and others involved in animal and human screening and sample collection
Exposed during patient care and sampling, including
- Healthcare workers treating patients with confirmed zoonotic influenza virus infections
- Close contacts of infected patients, particularly in healthcare or caregiving settings
Travelled to regions with high virus circulation, including
- Individuals living in or traveling to areas where H5N1 or other zoonotic influenza subtypes are known to circulate widely, especially for professional reasons. Risk is particularly elevated in live/wet poultry markets, where large numbers of birds are kept and slaughtered under stressful, crowded conditions.
[1] These high risk groups might change according to potential risk assessments from ECDC or RAG and RAG-V-EZ
[2] Animals known to be susceptible to zoonotic influenza include (but are not limited to): Wild birds as a primary reservoir for avian influenza viruses, Poultry, Wild mammals (foxes, bats,…), including marine mammals such as seals, farmed animals including pigs, fur animals (mink, ferrets), cattle (bovines, goats, alpacas, horses), Domesticated mammals including pets (cats and dogs)
- Q9. What are the symptoms and complications of zoonotic influenza?
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The initial symptoms of zoonotic influenza viruses are similar to those caused by seasonal influenza: fever, cough, and other signs of a respiratory infection. Gastrointestinal symptoms and neurological symptoms (including encephalitis of unknown cause) may also occur.
Conjunctivitis has been frequently reported among recent U.S. cases of zoonotic influenza A(H5) virus infection associated with infected cattle, likely related to manual inoculation of the virus into the eye during the milking process.
The severity, marked by pneumonia, acute respiratory distress syndrome (ARDS) , and multi-organ failure, may depend on the specific subtypes involved and individual risk factors (immunosuppression, age over 65, chronic respiratory or cardiovascular disease, etc.)[1].
- Q10. What do I do if I suspect my patient is infected by influenza of animal origin ?
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If a patient has been exposed to infected, sick or dead animals and shows symptoms compatible with zoonotic influenza, it is legally mandatory to notify the Regional Health Authorities (RHA) (see Appendix for contact information) as soon as there is a clinical suspicion. Do not wait for a test confirmation. RHA will assess whether isolation, testing for laboratory confirmation, contact tracing, antiviral post-exposure prophylaxis or antiviral treatment is required.
- Q11. What do I do if a person is exposed to an infected animal with influenza virus?
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If the person is exposed, the regional health authorities (RHA) will assess the exposure risk and whether the individuals has symptoms.
- If the person has been exposed and is showing symptoms, refer Q10.
- If asymptomatic,
- Notify the RHA (see Appendix for contact information)
- Person has to self-monitor for the development of symptoms for a period of 14 days following the last exposure to the infected animal(s). If the person becomes symptomatic, they should contact the RHA.
- Depending on the level of exposure risk, an asymptomatic individual may be eligible for post-exposure prophylaxis. If applicable, the RHA will contact the person directly to explain the next steps. Asymptomatic exposed person might be eligible to participate on a voluntary basis in a Belgian pilot surveillance study called ZOOIS, which involves testing asymptomatic individuals exposed to infected animals. Participant recruitment is coordinating through the designated RHA (see Appendix for contact information).
- Q12. What do I do if a person is exposed to a confirmed zoonotic influenza human case ?
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As part of the case investigation, the Regional Health Authority (RHA) will initiate contact tracing to identify all individuals at risk who have been in contact with the confirmed human case. The RHA will reach out to all identified contacts and implement appropriate management measures including symptom monitoring. These also may include testing, quarantine, and antiviral post-exposure prophylaxis, depending on the level of exposure. If someone has been exposed to a confirmed human case of zoonotic influenza and has not yet been contacted by the RHA, they should proactively reach out to their local RHA for guidance (see Appendix for contact information).
- Q13. What type of personal protective equipment (PPE) should I wear?
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The choice of PPE will depend on the level of exposure.
Recommended PPE for the care of hospitalised patients or in case of aerosol-generating procedures include
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a well-fitted FFP2 or FFP3 respirator
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gown
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gloves
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eye protection
When performing a nasopharyngeal swab, PPE can be limited to a respirator mask, eye protection and gloves.
Recommended guideline:
European Centre for Disease Prevention and Control. Considerations for infection prevention and control in relation to respiratory viral infections in healthcare settings. 6 February 2023. ECDC: Stockholm; 2023.
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- Q14. What kind of testing should I perform to confirm the diagnosis?
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The gold standard for detection and identification of zoonotic influenza from respiratory samples is RT-qPCR. It is advised to test, where possible, on the day of symptom onset, using either a nasopharyngeal swab or combination of nasal and throat swabs. In case of a conjunctivitis, conjunctival wash can be taken as well. If the patient is hospitalized and nasopharyngeal sample is negative, broncho-alveolar fluid may be collected for further analysis. Sample collection should be performed in a hospital setting and not in a general practitioner’s office.
Serology is not recommended as routine diagnosis tool for zoonotic influenza. However, it may be useful in certain cases, such as when symptom onset occurred more than 14 days ago, or to help differentiate true infections from environmental contamination of the mucosa. The limitation of serological testing should be taken into account, including, the potential cross-reactions between subtypes or lineages of subtypes. If serological testing is performed, acute-phase serum specimens should be taken at exposure and 2-4 weeks after symptom onset to identify seroconversion.
Each sample collected from a suspected case must be sent to the National Reference Center (NRC) for respiratory pathogens (refer Q15).
As of 01.01.2025, the former NRC for Respiratory Pathogens and the NRC for Influenza have been merged into a single, expanded NRC for Respiratory Pathogens, coordinated by UZ Leuven/KU Leuven.
However, all influenza samples, including suspected zoonotic influenza, must still be sent to the Sciensano site at the address provided below (refer Q15). - Q15. How should I send the sample to the National Reference Center for respiratory pathogens ?
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Each sample collected from a suspected or confirmed human case must be sent to the National Reference Center (NRC) for respiratory pathogens.
02/ 373.31.11
T.a.v. National Reference Center for Respiratory Pathogens
Viral diseases – Sciensano
Engelandstraat 642 1180 Brussels - België
Contact: respivir@sciensano.be
As of 01.01.2025, the former NRC for Respiratory Pathogens and the NRC for Influenza have been merged into a single, expanded NRC for Respiratory Pathogens, coordinated by UZ Leuven/KU Leuven.
However, all influenza samples, including suspected zoonotic influenza, must still be sent to the Sciensano site at the address provided above.Specimens for transport must be placed in leak-proof triple specimen bags, which have a separate sealable pocket for the specimen (i.e. a plastic biohazard specimen bag).
Personnel who transport specimens should be trained in safe handling practices and decontamination procedures in case of a spill. The laboratory must be notified by telephone when the specimen is on its way. Time between sampling and delivery at the laboratory should be as short as possible. Before sending, samples should be stored at +/-4°C.
Samples must always be accompanied by a completed analysis request form. Special attention should be provided to fill in data on possible animal contacts, symptoms and epidemiological links.
- Q16. What do I do if the patient needs to be hospitalised?
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If not already done, notify the responsible Regional Health Authority that you suspect a case of zoonotic influenza. Severe cases that require hospitalisation (e.g. for oxygen administration) should be sent to hospitals that have an available negative-pressure isolation room with anteroom, such as those used for hospitalised patients with open pulmonary tuberculosis.
- Q17. What is the treatment for zoonotic influenza in humans?
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Oseltamivir is the recommended first-line antiviral. The recommended dosage of orally oseltamivir for adults and children >13 years*: 75 mg orally twice daily for 5 days. Oseltamivir be administered to pregnant and lactating women and children, including neonates[1].Treatment should be initiated as early as possible for confirmed cases, within 24-48 hours from onset of symptoms.
*For children 1 to 12 years of age [2]
- Bodyweight <10kg: 3mg/kg orally twice daily for 5 days;
- Bodyweight 10-15kg: 30mg orally twice daily for 5 days;
- Bodyweight 15-23kg: 45mg orally twice daily for 5 days;
- Bodyweight 23-40kg: 60mg orally twice daily for 5 days;
- Bodyweight >40kg: 75mg orally twice daily for 5 days.
Annex - Regional Health Authorities contact information for notification
| Departement Zorg — Flanders |
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| AVIQ — Wallonie |
Direction Surveillance des Maladies Infectieuses de l’AVIQ
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| Vivalis — Brussels |
Cellule de Médecine préventive et gestion des risques sanitaires de Vivalis
Si besoin d’un contact direct avec un médecin : |
| Ministerium der. Deutschsprachigen Gemeinschaft |
Hygieneinspektion der Deutschsprachigen Gemeinschaft
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