Kiri

To:         National Focal Points for Viral Respiratory Diseases, Operational Contact Points for influenza

Cc:         National Coordinators  

Dear colleagues,

With this email we would like to raise your attention to the ECDC and joint ECDC/EFSA published documents related to avian influenza prevention and response measures, including enhanced surveillance and targeted testing in humans.

Highly pathogenic avian influenza (HPAI) A(H5N1) viruses continue to be widespread in wild bird populations across the EU/EEA. Viruses circulating in wild birds can spillover to both wild and domestic animals, leading to outbreaks in poultry and occasional cases in mammals. ECDC publishes together with EFSA a quarterly avian influenza monitoring report with more information on the epidemiological situation and human cases globally. The latest report can be found here: ECDC/EFSA quarterly monitoring report.

A public update, including updates for ongoing events (including the US A(H5N1) cattle transmission event and associated human cases) is also provided regularly through the ECDC Communicable Disease Threats Report (CDTR). The latest CDTR can be found here.

Prevention and response measures related to infections in humans

Although human infections from currently circulating 2.3.4.4b A(H5N1) influenza viruses remain rare despite widespread transmission among animals, sporadic human cases among exposed individuals can be expected. Active monitoring and testing of exposed persons to infected animals is recommended for early detection of human cases and to assess the possibility of human-to-human transmission. Enhanced surveillance should be considered in the context of the ongoing avian influenza outbreaks in animals; more information on the relevant ECDC documents is given below.

Follow-up of people exposed to animals infected with avian influenza and targeted testing

ECDC has published an Investigation protocol for human exposures and cases of avian influenza in the EU/EEA that sets out measures for the follow-up and management of individuals exposed to infected animals and human cases of avian influenza, and for the public health management of possible and confirmed human cases of avian influenza. People exposed to infected animals should be followed up to identify early transmission from animals to humans, as well as between humans. 

The protocol recommends that follow-up should last between 10 to 14 days after last exposure. This could involve active follow-up, where health authorities contact the individuals daily or frequently to check for the onset of symptoms, or passive follow-up, which might include daily self-checks and reporting of health status.

If individuals develop symptoms, which could range from fever, conjunctivitis, and diarrhoea to respiratory, neurological, or other atypical symptoms, immediate testing should be undertaken, and the individuals should isolate. Those who have been in close contact with confirmed cases should also be tested and monitored to prevent further spread and to track transmission. Testing of asymptomatic individuals who have been exposed may be conducted on a case-by-case basis, taking into account the level of exposure.

Given the uncertainties related to mammal-to-mammal transmission and according to the epidemiological situation, a low threshold for testing persons exposed to potentially infected mammals can be considered (for example symptomatic individuals with conjunctivitis or respiratory symptoms). Serological testing can be applied in the context of avian influenza outbreaks in the area and follow-up studies to evaluate the seroconversion upon exposure and support the overall risk assessment for zoonotic transmission.

More information on testing and detection of zoonotic influenza virus infections in humans in the EU/EEA, and occupational safety and health measures for those exposed at work can be found at the joint ECDC/EFSA/EU-OSHA/EURL operational guidance ‘Testing and detection of zoonotic influenza virus infections in humans in the EU/EEA, and occupational safety and health measures for those exposed at work’.

Enhanced avian influenza surveillance to identify human infections

ECDC published jointly with WHO Euro operational considerations for respiratory virus surveillance in Europe that describe how to strengthen and design surveillance systems for respiratory viruses to fulfil different surveillance objectives. Particularly, sentinel surveillance systems in primary and secondary care are considered important for the monitoring of respiratory viruses in the EU/EEA, but these systems are not designed and powered to early identify a newly emerging virus such as avian influenza in the general population and to implement control measures. Ideally all influenza positive specimens from sentinel sources should be typed and subtyped. Surveillance of influenza and other respiratory viruses should be expanded throughout the whole year.

ECDC has published surveillance guidance documents with considerations regarding the monitoring of avian influenza during both the influenza season and the inter-seasonal periods: ‘Targeted surveillance to identify human infections with avian influenza virus during the influenza season 2023/24, EU/EEA’ and ‘Enhanced surveillance of severe avian influenza virus infections in hospital settings in the EU/EEA’ respectively. Below we provide a summary of aspects that are considered in these documents. During the influenza season, a risk-based approach has been suggested based on the knowledge of avian influenza outbreaks in specific geographical areas; testing and sub-typing approaches for avian influenza virus need to be proportionate to the epidemiological situation and the capacities of reference laboratories.

During periods of very low seasonal influenza circulation, enhanced surveillance for hospitalised cases should be considered in all geographic locations irrespective of the presence of know avian influenza outbreaks.

Specifically:

• Clinicians should collect the history of exposure to sick or dead animals of patients hospitalised with respiratory symptoms. This exposure risk assessment should inform the decision to test for avian influenza A(H5).

• Specimens from hospitalised patients with very severe influenza A virus infection should be considered for further subtyping. During the summer period that we are soon entering, subtyping all hospitalised cases of influenza A can be considered to detect unexpected cases of avian influenza.

• Hospitalised patients with unexplained viral encephalitis or meningoencephalitis should be tested for seasonal influenza virus. If the influenza A virus is detected, further subtyping should be performed to exclude avian influenza.

• In addition, clusters of severe respiratory infections requiring hospitalization should be investigated. If routine testing for respiratory pathogens yields inconclusive results, tests for avian influenza should be carried out.

• In general, any laboratory-confirmed influenza A positive sample that does not subtype as seasonal influenza virus (i.e., gives a negative result for both H3 and H1pdm09) from sentinel or non-sentinel primary or secondary-care sources should be tested specifically for the avian influenza H5 subtype.

• Positive samples for A(H5) should be sent to the national influenza reference laboratories for further confirmation.

• All A(H5) positive samples should be sequenced.

• Positive samples should be sent to the WHO Collaborating Centre for further characterisation.

• Laboratory-confirmed cases need to be reported to WHO under the International Health Regulations (IHR) (2005) and according to EU regulations, they are notifiable to the Early Warning Reporting System (EWRS), Epipulse and the European Surveillance System (TESSy).

Finally, wastewater surveillance could be considered as an additional monitoring system locally, although so far there is very limited experience in using this method to identify low-level circulation of zoonotic influenza virus infections in the human population.

Other options for preventive measures

Options for One Health mitigation measures in the human and animal sectors to reduce the potential of transmission to humans as well as the drivers and critical steps for a pandemic due to avian influenza are discussed in the joint ECDC/EFSA technical report ‘Drivers for a pandemic due to avian influenza and options for One Health mitigation measures’. In order to protect human health, a strong collaboration between the animal and human sectors is critical.

Diagnostic accessibility: Access to diagnostic processes, including genomic technologies should be ensured.

Minimizing exposure: Appropriate personal protective equipment according to the level and type of exposure together with stringent hygiene, biosafety, and biosecurity measures to minimize exposure can be employed. Due to the higher risk of infection for individuals exposed to infected animals and contaminated environments, appropriate personal protective equipment and other precautionary measures should always be taken to reduce the risk of infection.

Public communication: The risks of exposure and human infection by avian influenza to the public and how it can be mitigated should be communicated and awareness-raising programs should be targeted for multiple audiences, under a One Health plan, as discussed in the ECDC document ‘Investigation protocol for human exposures and cases of avian influenza in the EU/EEA’. Guidance tailored to specific occupational groups, or people engaged in recreational activities where additional measures may be beneficial, should be provided.

Antiviral treatment: Antiviral drug treatment can be administered to humans infected with avian influenza as soon as symptoms appear; post-exposure prophylaxis can also be considered.

Seasonal influenza vaccination: Vaccination against seasonal influenza to minimize the risk of virus reassortment between avian and human influenza strains can be considered, adhering to the vaccination recommendations by national authorities. Vaccination should be complemented with other preventive measures as appropriate.

Avian influenza A(H5) vaccination: Immunization against influenza A(H5) for individuals occupationally exposed could be considered. Specific vaccination recommendations are under the remit of national authorities.

More information on the preparedness measures that countries have implemented and laboratory capacities and capabilities to detect and characterise zoonotic influenza viruses can be found in the two ECDC survey reports here: Survey report on laboratory capacity for molecular diagnosis and characterisation of zoonotic influenza viruses in human specimens in EU/EEA and the Western Balkans and EU/EEA country survey on measures applied to protect exposed people during outbreaks of highly pathogenic avian influenza. An updated survey focused mainly on surveillance and targeted testing is currently ongoing.

If you need more information or support, please contact [email protected]

Best regards,

The ECDC Respiratory Viruses and Legionella group