A lot of concern has been raised about H5N1 bird flu and the potential risk to humans. In this post we'll take a deep dive to examine what we know (and don't know) about the death rate so far. One fact which is often mentioned is that H5N1 has killed nearly 60% of those infected. But at the same time, the only symptom was pink eye when Texas announced its first human case. So what's the truth? First of all, it's important to understand that H5N1 has been around for many years. Like coronavirus, this strain of bird flu is constantly evolving - the variants today are not the same as the ones from the late 90s. In total, 907 people have been infected with H5N1 bird flu since the first outbreak in Hong Kong in 1997, causing 469 deaths (a case fatality rate of 52%). Today, the predominant variant is clade 2.3.4.4b, which emerged in late 2020 and caused major outbreaks in wild birds and poultry around the world, reaching Antarctica just a few months ago. During this period we've seen increasing spillover to other hosts - cats, dogs, sea lions, foxes, otters and many other mammals. More recently, dairy cows in the U.S. have been infected with the virus. However, most of the human cases (486 out of 907) happened before 2010. Only 29 human cases have been reported since 2020, of which 13 were caused by this new variant. Out of those 13, four patients became seriously ill and one of them died, a 38-year-old woman from China in 2022. This means the new variant has a case fatality rate of 8%. At first glance, this is good news – 8% is high yet much lower when compared to 52%. But this data comes with important caveats, making it difficult to draw any firm conclusions. Nine of the 13 cases were the result of increased surveillance among poultry workers and would have gone unnoticed nearly everywhere else. 7 were completely asymptomatic, 2 were very mild. Those cases, the result of random surveillance, skews the data as they were not full-blown infections. If we exclude them, we are left with only 4 cases, all of which became seriously ill (including the woman who died). At the same time, testing for bird flu remains extremely rare, and when it does happen (beyond random surveillance) it's skewed towards severe cases, which means milder cases from contact with poultry will go undetected. In conclusion, we know H5N1 bird flu is capable of causing severe illness in humans, both in children and adults, but there's not enough data to determine the death rate in a pandemic.
@BNOFeed Good breakdown and objective, appreciate the handling of