Could Bird Flu Kill 50% of Humanity?

Last week, the World Health Organization (WHO) held a briefing on H5N1, a strain of Avian Influenza more commonly known as Bird Flu. Following the briefing, we came across the following short headline being shared and repeated widely on social media – “Bird Flu may mutate to kill more than 50% of humanity.”

While the full article first published by The Daily Mail has a longer headline with more detail, the shorter version with less context is what appears when the article is shared on social media. We have observed the specific phrasing above being brought up and discussed across different social media platforms over the past week.

While some have reacted with alarm and fear, others are alleging that the WHO is fear mongering as part of a larger conspiracy. We looked for answers to two questions this claim raises. Could bird flu possibly mutate into a deadly human-transmissible virus? And, could it really kill 50% of humanity?

According to the WHO briefing and a recently published research article, there is indeed increasing concern about the possible spread of H5N1 across mammals instead of the virus being confined mainly to birds. Recent outbreaks of H5N1 among mammals such as minks, foxes, otters, and seals could signal a mutation in the virus which allows higher, sustained transmission between mammals rather than primarily from direct contact with infected birds.

As of now, a very small number human-to-human bird flu transmission cases have been recorded. So far, they have been “limited” and “non-sustained,” without resulting in widespread infection. However, recent research on mammal infections, and the subsequent briefing from the WHO has sparked new concern about the possibility of the virus mutating to allow sustained transmission between humans. WHO director-general Tedros Adhanom Ghebreyesus has been widely quoted cautioning that, “we must prepare for a potential bird flu pandemic.”

Despite these alarming-sounding findings, researchers have also pointed out that the likelihood of the virus mutating enough to impact humans is still low. The virus would have to mutate significantly more than it has in animals to adapt to the human body. Only 2 cases have been identified in the past year and both individuals have survived the infection. There is, as of yet, no indication that humans can contract the virus from other infected mammals instead of directly from infected birds.  The WHO itself also currently identifies bird flu as being of low risk to humans. Therefore, while the possibility remains and should be taken seriously, the probability is, as of now, low and should not be cause for widespread panic.

But, if the mutation of the virus does stretch to humans in the future, could it possibly kill half of humanity? In humans, the estimated mortality rate of H5N1 is about 50%, which is where the headline “50% of humanity” comes from.

It is important to note that “mortality rate” is a measure of death frequency within a particular group of people; in this case, individuals who have contracted H5N1. A 50% mortality rate therefore means that 50% of the individuals diagnosed with H5N1 did not survive it.

The context behind this statistic is that only a relatively low number human infection cases of H5N1 have been recorded worldwide since it was first identified in 1997 (about 880 cases over 27 years), mostly in individuals exposed closely to infected birds. This is where the approximate mortality rate is derived, which makes it harder to accurately predict mortality in event of a widespread flu pandemic among humans.

The WHO briefing also discussed how H5N1 is more likely to cause intense damage to human lungs because the humans are not the main carrier of the virus. If the virus does adapt to humans, it would likely have different characteristics. In addition, some researchers have pointed out that reported cases are likely skewed towards more serious ones, with milder cases possibly undiagnosed or unreported.

Therefore, while the possibility that “bird flu may mutate to kill more than 50% of humanity” cannot be eliminated entirely, it is far from a certainty based on current research and is an inaccurate conclusion based on the 50% mortality rate. This would be a worst-case scenario rather than an impending threat. We give this specific claim a rating of likely false because of its misleading nature. It has been used in isolation as a fact without significant accompanying context.

It is important to be clear about the probabilities rather than just focusing on an eye-catching headline. While not technically inaccurate, the headline being spread in its condensed form contributes to misinformation, breeding further conspiracies across social media – something we have already observed on Twitter and TikTok.

The H5N1 situation is undoubtably serious and a problem that also affects food supply and biodiversity. Being aware of the ongoing updates from the WHO, well-researched news articles, and peer-reviewed research is key to understanding the bird flu situation and will help us as readers be less susceptible to suggestive, inaccurate headlines.