We've been following the expansion of HPAI H5N5 both in Europe - and in Canada - for the better part of two years. While we'd seen reports of H5N5 in European birds going back to 2016, it was detected in dead raccoons on Prince Edward Island about 20 months ago (see CIDRAP Report Canada reports first H5N5 avian flu in a mammal).
Last spring we began to see increased reports of H5N5 (see WAHIS: More Reports of HPAI H5N5 in Canada), and last July, in Cell Reports: Multiple Transatlantic Incursions of HPAI clade 2.3.4.4b A(H5N5) Virus into North America and Spillover to Mammals, researchers reported finding the mammalian adaptive E627K mutation in a number of samples.
In the most recent ECDC/EFSA Quarterly Avian Influenza Overview Sep 2024 - Dec 2024, there were several mentions of HPAI H5N5, including:
- HPAI A(H5N5) viruses continued to expand their geographic and species range, and were reported in wild birds in several countries. Further spillover to domestic birds was observed in Iceland, Norway and the United Kingdom. A study on A(H5N5) in wildlife in Canada suggested that northern fulmars were acting as source species for this subtype.
- The geographic expansion of HPAI A(H5N5) viruses in wild birds, which were found in increased numbers around the coast of the United Kingdom in the current reporting period, should continue to be closely monitored in northern parts of Europe and worldwide.
Today we have a (translated) announcement from the Icelandic Food and Veterinary Authority (MAST) on the fatal infection of a kitten with H5N5. At least two other cats from this household died, but were not tested.
News - 07.01.2025
The Icelandic University of Iceland's Pathology Laboratory at Keldur notified the Icelandic Food and Veterinary Authority on January 6 that a kitten that arrived at the laboratory for autopsy had been diagnosed with a severe strain of avian influenza (H5N5). This is the same strain that has been detected in wild birds in Iceland since September last year and on one poultry farm in early December. The Icelandic Food and Veterinary Authority immediately issued instructions for disease control to prevent the spread of the infection and is now working to trace the infection. Symptoms of the disease in this cat included loss of appetite, weakness, stiffness, tremors, seizures and other neurological symptoms. Cat owners are asked to contact a veterinarian immediately if they notice such symptoms in their cats.
The cat diagnosed with bird flu was a 10-week-old kitten that died on December 22. The littermate the kitten was from and another kitten from the same litter died after a short illness two days earlier. They were not tested. The kitten's other littermates had left the home before the illness occurred and are all asymptomatic today. The cats are from Ísafjörður, but the kitten diagnosed with the infection had arrived in Reykjavík. The owners of all the cats have been contacted.
The Icelandic Food and Veterinary Authority believes that it is most likely that the cats were infected by an infected wild bird. At present, there is no evidence of infection in more cats, but the Icelandic Food and Veterinary Authority asks cat owners and veterinarians to be on the lookout for symptoms that may indicate avian influenza infection. There have been a number of diagnoses in wild birds in recent months, and therefore there is some risk that cats can become infected while hunting or from carcasses they come across.
However, the Icelandic Food and Veterinary Authority does not believe the risk is so great that there is reason to warn against letting cats outside. People are, however, reminded to always maintain general hygiene when interacting with animals and caring for them. General information about avian influenza and guidelines for disease prevention can be found on the website of the Directorate of Health . It is worth noting that the risk of infection for people caused by the avian influenza virus is low, according to information on the website of the European Centre for Disease Prevention and Control (ECDC) .
In recent years, avian influenza has been increasingly detected in various species of mammals around the world. The most common type is the highly pathogenic H5N1 strain. This trend clearly demonstrates the virus's ability to adapt to new animal species. One of the greatest concerns worldwide is the current outbreak of avian influenza in dairy cows in the United States caused by the highly pathogenic H5N1 strain. However, the genotype of the virus in question has not yet been identified anywhere else in the world. Detailed information about this can be found on the websites of the United States Department of Agriculture USDA and the United States Centers for Disease Control and Prevention ( CDC) .
Few cases of the virulent H5N5 strain have been reported in mammals. This strain has been mainly found in wild birds in the Arctic, but last year it was also found in red foxes and lynx in Norway, otters in the Netherlands, lynxes in Finland, and red foxes, skunks, and raccoons in Canada. No cases of this strain in domestic animals have been reported to the World Organisation for Animal Health (WOAH) to date.
In recent years, WOAH has placed great emphasis on combating the spread of avian influenza and published on its website in December a call for all nations of the world to place greater emphasis on monitoring and actions to prevent the spread of dangerous avian influenza viruses.
The Icelandic Food and Veterinary Authority reiterates its recommendation to the public to report wild birds and wild mammals found dead, when the cause of death is not obvious. This is best done by registering a tip on the Icelandic Food and Veterinary Authority website. It is important to clearly describe the location, preferably by recording coordinates.
The WOAH WAHIS report # 171395 provides this brief epidemiological comment:
SOURCE OF EVENT OR ORIGIN OF INFECTION
- Unknown or inconclusive
EPIDEMIOLOGICAL COMMENTS
Three cats (one adult female and two 10 week old kittens) from the same household died on December 20., 21. and 22. after they had been ill for only a few days. The main clinical signs were lethargy, anorexia, cramps and stiffness. Other kittens from the same litter had been rehomed before those three got sick and they have not shown any symptoms. The most probable source of infection is wild birds. HPAI H5N5 have been diagnosed in a few wild birds in Iceland since September last year.
While our biggest concern remains HPAI H5N1, over the years we've seen closely related H5N2, H5N3, H5N4, H5N5, H5N6, and H5N8 viruses - the product of H5N1 reassorting with other LPAI viruses - infecting both birds and mammals around the globe.
It is not impossible that we could that threat shift - from H5N1 to H5N5, or H5N6, or to some other n-type, in the months or years ahead. The H5Nx virus has an large - and growing - array of diverse hosts to inhabit, and no lack of genetic diversity on which to draw.
All reasons why we should fully expect to see additional surprises in the future.