ECDC: Enhanced Influenza Surveillance to Detect Avian Influenza Virus Infections in the EU/EEA During the Inter-Seasonal Period

#18,137

In the Northern Hemisphere the period between early May and October is considered the inter-seasonal period where influenza activity is generally low, and the more rigorous influenza surveillance of winter is largely scaled back.  

Influenza doesn't completely go away, of course.  And there are a number of non-influenza respiratory viruses that often spread over the summer.  So people continue to fall ill during this time, and are sometimes hospitalized with `viral infections'.

This year, we have increasing concerns over the possible spillover of H5N1 - from both birds and animals - to humans.  While most of the attention has been in the United States the past few months, Europe has seen numerous outbreak among farmed animals, and even domestic pets, over the past year. 

The problem is, the symptoms of human H5N1 infection are pretty much the same as with any influenza virus, and there is no way of identifying cases without enhanced laboratory testing.  

While only 3 cattle-linked human H5N1 infections have been reported in the United States, it is widely believed  - based on anecdotal reports of sick dairy workers that were never tested - that some cases have likely been missed over the past 4 months.  

And as we saw in last year's analysis from the UKHSA (see TTD (Time to Detect): Revisited), there could be dozens of undetected cases of human H5N1 infection before public health would likely detect them, perhaps even hundreds. 

As today's ECDC summary points out: 

Sentinel surveillance systems are important for the monitoring of respiratory viruses in the EU/EEA, but these systems are not designed and are not sufficiently sensitive to identify a newly emerging virus such as avian influenza in the general population early enough for the purpose of implementing control measures in a timely way.

While it is not expected to catch every human H5 infection, today the ECDC has offered up guidance to the EU/EEA member nations on how to better their chances of detecting H5N1 in severe and hospitalized patients. 

The full 7-page PDF is well worth perusing, but I've posted the executive summary below. I'll have a brief comment after the break. 

Enhanced influenza surveillance to detect avian influenza virus infections in the EU/EEA during the inter-seasonal period

Surveillance and monitoring
20 Jun 2024

Highly pathogenic avian influenza A(H5N1) viruses continue to be widespread in wild bird populations across the European Union/European Economic Area (EU/EEA). Viruses circulating in wild birds have spilled over to both wild and domestic/farmed animals, leading to outbreaks in poultry and other animal farms.

Executive summary

Transmission to humans can occur when avian influenza is circulating in animals, especially when people are directly exposed without wearing appropriate levels of protective equipment, with an estimated low-to moderate risks for individuals exposed. During the summer months, seasonal influenza virus activity tends to be very limited, resulting in few cases of seasonal influenza infection and even fewer cases of hospitalisation and severe disease.

Ideally, all influenza positive specimens from sentinel sources should be typed and subtyped, augmented by year-round surveillance of influenza and other respiratory viruses. Sentinel surveillance systems are important for the monitoring of respiratory viruses in the EU/EEA, but these systems are not designed and are not sufficiently sensitive to identify a newly emerging virus such as avian influenza in the general population early enough for the purpose of implementing control measures in a timely way.

To identify sporadic severe human infections with avian influenza virus in hospital settings, the following approach is proposed:

• People admitted to hospitals with respiratory symptoms or other symptoms compatible with avian influenza virus infection should be asked about exposure to birds (wild birds or poultry) or other animals (dead or alive) in the two weeks before symptom onset or, if not available, before admission.
• Patients admitted to the hospital due to respiratory or other influenza related symptoms should be considered for influenza A/B testing. Testing for influenza virus of hospitalised patients with unexplained viral encephalitis/ meningoencephalitis in whom a causative agent cannot be identified should be considered.
• All influenza A-positive samples from hospitalised patients should be subtyped for seasonal influenza viruses A(H1)pdm09 and A(H3).
• Samples positive for influenza type A virus but negative for A(H1)pdm09 or A(H3) should immediately be sent to national influenza reference laboratories for further testing, subtyping and genetic analysis. Member States should ensure they have sufficient laboratory capacity to meet this need and future demands.

Raising awareness among all primary care workers and communicating the epidemiological situation is important in order to not miss or delay diagnosis of potential human cases. Raising awareness in primary care providers including consideration of specific enquiring about animal exposure would be a good practice: people who seek medical care during the summer period with respiratory or other symptoms compatible with avian influenza virus infection be asked about history of exposure to dead or sick animals within the two weeks before symptom onset, especially when there are ongoing outbreaks among animals in the area.

Primary care clinicians should be educated on symptoms compatible with avian influenza infections and testing of symptomatic persons with a history of exposure should follow a risk-based approach according to the level of exposure as proposed in the published ECDC guidance documents ‘Investigation protocol of human cases of avian influenza virus infections in EU/EEA’ and ‘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’.

ECDC encourages national public health authorities to provide messaging to the general public to avoid close contact with or touching of sick or dead birds (especially seabirds and wildfowl) and dead wild mammals.

Enhanced test of severe avian influenza virus infections - EN - [PDF-317.68 KB]

Over the past 3 months we've seen our own CDC offer up reams of guidance to states and territories on how they should deal with H5N1 (see here, here, here, here, and here), but the ultimate decision to follow them lies with local and state authorities. 

The same applies with ECDC, which may only present non-binding recommendations to member states.

There is also the problem that not every member nation is fully equipped to conduct enhanced surveillance and testing.  In last year's Lancet Preprint: National Surveillance for Novel Diseases - A Systematic Analysis of 195 Countries, researchers found while European nations generally fared better than many other regions, significant gaps still exist. 

The bottom line is while the increased attention and guidance by ECDC is certainly welcome, we'll need more than a little bit of luck to detect early community spread of H5N1, even if it begins in high income countries.