The State of Avian Flu, H5N1, March 2023
Our team at Virax Biolabs is committed to carefully monitoring the events of the current avian flu pandemic in animals, which has been driven largely by the highly transmissible subtype H5N1.
Given all the media coverage of this strain, we know there has been a lot of concern about what this virus means for all of us, so our team will be briefing you with the latest on the state of this outbreak as it continues.
Let’s clarify what we know so far:
What is H5N1? As its common name suggests, H5N1 is one version of the avian flu that has historically circulated mainly in marine bird populations. H5N1 is a subtype of influenza A, which means that there are various strains that fall under the H5N1 umbrella. Some of these are considered to be less threatening, while others are considered highly pathogenic, like the strains driving the current outbreaks (1).
H5N1 is not a new subtype: first detected in China in 1996, the World Health Organisation (WHO) has been tracking outbreaks of concern since 2003 (2). However, since the last half of 2022, it has become clear that the strains driving the newest H5N1 outbreaks are unlike any of those that we have seen before. It has seemingly outflanked other subtypes of previous concern like H7N9, which drove a 2013 outbreak in China.
Where and how is it spreading? This H5N1 outbreak has reached unprecedented scale as it is now considered endemic in various migratory bird species (3). This has led to what many experts consider to be the worst animal-disease outbreak in recent history as H5N1 has been found in numerous countries, most notably in exposed poultry flocks.
While the exact number of countries affected is currently unclear, there have been notable outbreaks in most of South America, the USA, China, Mexico, the UK, France, and Japan (4). At the moment, there are major concerns about sprawling transmission stemming from the anticipated spring migration patterns of wild bird populations (5).
We also know that there have been numerous cases of bird-to-mammal transmission outside of humans, as we have seen cases in foxes, seals, minks, skunks, and even bears. While most of these cases are reportedly due to animals consuming sick or dead birds that had high viral load, the mink farm outbreak in Spain was seen as particularly concerning because there was strong evidence of mammal-to-mammal transmission.
How deadly is it? For chickens? It is extremely deadly – with mortality rates estimated to be close to 100% (6).
For people? It is harder to say. Of the 868 cases of H5N1 recorded from January 2003 to 26 January 2023, 457 cases were reported as fatal. Therefore, the WHO reports a case-fatality proportion of almost 53% (7).
However, let’s remember that these cases have been extremely rare so far, and they typically accounted for those who were extremely ill. Furthermore, some academics are convinced that actual fatality rate is much lower (8). That does not mean we should rest easy, though. While some estimates of case-fatality place closer to the 0.1-2.5% range similar to prior flu pandemics, some estimates place the rate in the range of 14-33% (9). There is not enough evidence for us to say for sure.
How are countries dealing with the outbreaks? While the exact prognosis remains unclear, one thing that is clear is that countries around the world are mobilizing their resources to contend with these outbreaks.
Most prominently, we have seen ten countries in South America report states of emergency since the fall of 2022, with Argentina and Uruguay becoming the latest to join (10).
China has vaccinated its poultry stock for nearly two decades, and other countries are expected to follow its lead. México authorized emergency vaccinations last year, with Ecuador and France expected to follow this year. The Biden administration has been assessing this approach for the USA, the largest poultry producer in the world. Hesitancy for poultry vaccination may be declining throughout the West, as Europe continues to see positive results from trials in the Netherlands and pending results elsewhere (11).
Almost universally, farmers have been forced to cull their animals in order to contain transmission.
Should I be concerned? Currently, the good news is that the threat to most people appears to remain low. During this outbreak, there has not been any reported case of human-to-human transmission, and the people who have contracted bird flu appeared to have been in close contact with infected birds. However, any good public health practitioner is likely to sound caution that we are simply a few mutations away from a full-blown pandemic.
We can understand how these developments are concerning or scary, but at present, we can take solace that the threat to general public health remains low. We can all agree that we hope that these outbreaks are contained without producing the necessary mutations to cause a pandemic.
However, should H5N1 mutate further to allow mammal-to-mammal transmission and human-to-human transmission, we at Virax Biolabs are ready to assist governments and firms alike by providing the necessary diagnostic tools to aide public health efforts in all vulnerable regions.
As part of our ViraxClear distribution platform, the Avian Influenza A (AIV) real-time PCR kit is available to locales accepting the CE mark and could be an invaluable instrument for people who face high occupational risk or exposure to H5N1, as well as the population as a whole.