is the bird flu worse than covid

Though COVID-19 is often referred to as a “once-in-a-century event,” this expression should not be taken literally. Another COVID-like pandemic at some point is almost inevitable, and the chances of a devastating pandemic materializing in any given year are low but constant. Recently, media figures have raised concerns that the highly pathogenic avian influenza virus A (H5N1) may have the potential to cause a pandemic. These concerns largely stem from probable transmission between minks late last year, which would constitute the first observed mammal-to-mammal transmission of H5N1.

An opinion piece by Zeynep Tufekci appropriately raises the alarm about H5N1 as a potential pandemic threat. Her piece may imply a higher probability of an H5N1 pandemic than is actually the case. But even with conservative assumptions, our forecasts indicate a roughly 4% chance of an H5N1 pandemic as bad as or worse than COVID-19 over the next year. If outbreaks in avian populations and spillover events return to baseline levels, then risk in subsequent years will be lower but still uncomfortably high. There are concrete steps the federal government can take to guard against that risk.

H5N1 is a subtype of influenza virus A, the kind of flu that causes pandemics. The modern strain of H5N1 was first detected in infected birds in 1996, and human cases and deaths were first confirmed in 1997. The virus spreads most readily between birds, though it has resulted in a total 887 confirmed human cases and 463 confirmed deaths, with most occurring 2004-2015. To date, known human infections have only occurred as a result of direct contact with infected birds, and there has been no observed human-to-human transmission.

The current clade of H5N1[ref 1], known as 2.3.4.4b, has infected hundreds of millions of birds worldwide since 2021, including at least 58 million birds in the U.S. alone and a similar number in Europe. This is the main driver of the recent spike in egg prices, as H5N1 has killed or caused the culling of millions of egg-laying hens. Beyond this horrible reality, the spread of H5N1 creates many opportunities for spillover into mammals (like humans!). The more avian-to-mammal cases occur, the more opportunities there are for genetic changes in the virus to optimize it for mammal-to-mammal transmission — which is probably what occurred in mink on a farm in Spain in October 2022, and possibly in sea lions as well. Human and bird viruses can combine in mink. This makes mink-to-human transmission a genuine pandemic risk.

H5N1’s likely spread between mammals poses an urgent question: will it cause a full-blown pandemic? Many experts hesitate to assign probabilities to this sort of question — reasonably, since forecasting the future is hard. But we need at least rough guesses of the relative likelihoods of different scenarios to inform how concerned we should be about particular threats and how best to prepare.

A good starting point for forecasting is to understand the relevant reference class—in this case, the frequency and characteristics of past influenza pandemics since 1900. The past is more often than not a useful guide to what might happen in the future. There have been five flu pandemics in this time frame, which implies an annualized probability of 5/122 ≈ 4% of a flu pandemic beginning in a given year. Only one of these pandemics, the Spanish Flu, was COVID-like in its impact on global mortality.[ref 2] COVID-19, according to excess mortality figures, has killed an estimated 20.8 million people. By this accounting, the probability of a flu pandemic that is COVID-like or worse starting in a given year is ~0.8% (1/122).

None of these recent flu pandemics were caused by H5N1, since so far H5N1 has never been observed to transmit between humans. Indeed, in its current form H5N1 cannot transmit between humans; thus far it has not acquired the mutations that facilitate binding to human airway receptors. One way to estimate the probability of something occurring that has never occurred is Laplace’s rule of succession,[ref 3] which in this case implies that, given there have been 0 H5N1 pandemics since the discovery of the modern form of H5N1 in 1996, there is a 1/29 ≈ 3.4% probability of it occurring in this next year.

These two methods are very rough and not in agreement (chance of a flu pandemic of any kind ≠ chance of an H5N1 pandemic). But they do guide our thinking: we can say that the percent chance of a flu pandemic starting in a given year is in the low single-digits, and that the chance of an H5N1 pandemic is probably not less than 1%.

Of course, the most relevant factors for our purposes are not related to the past, but are instead about the current situation. We have to account for the fact that the current H5N1 outbreak in birds is the largest ever outbreak of the H5N1 subtype of the virus, and that it is the first time probable mammal-to-mammal transmission has occurred. Since we do not have sufficiently reliable data to construct reference classes for an H5N1 pandemic, these are the author’s best guesses given his forecasting experience. Unfortunately, we do not have comprehensive historical data for any type of virus, given that large-scale genomic surveillance has only started in the last few years.

We can decompose the question of whether there will be an H5N1 pandemic into parts, keeping in mind the circumstances about our current situation. Each step is conditional on the previous step, and our objective here is to reason through the process that might lead to a pandemic from the current situation.

There is a 90% chance that sustained transmission of any kind among non-human mammals has already occurred or will soon occur.

There is an 85% chance notable genetic changes that facilitate airborne transmission in particular have occurred or will soon occur.

There is a 40% chance that the H5N1 virus from the above step is at least somewhat transmissible between humans.

There is a 20% chance that the H5N1 virus that meets the above minimum transmissibility is actually substantially transmissible between humans.

There is a 90% chance that a new H5N1 virus with a R0>1 would not be contained and would spread globally.

There is a 95% chance that the new H5N1 virus would result in at least 10k confirmed deaths.

There is a 80% chance that this new H5N1 virus would become a COVID-like pandemic or worse.

The above decomposition process leads to an overall ~4% chance of an H5N1 pandemic starting in the next year that is at least COVID-like in its impact. Since the total harms of COVID-19 to the U.S. are about $16 trillion, the expected cost of H5N1 is at least $640 billion — though it is probably far greater, since the mortality rate would probably be much higher than that of COVID-19. Yet we are hardly preparing for this costly possibility, though adequate preparation would cost far less than $640 billion. Our analysis does not take into account the annualized risk for all future years, so we are being very conservative in estimating the value of preventing an H5N1 pandemic.

COVID-19 was a clear reminder that low-probability, high-consequence events are worth taking seriously. The ~4% chance arrived at in this piece is just for H5N1, so it doesn’t account for the possibility of a different flu pandemic starting this year. There will also be a continued (albeit probably lower) risk of an H5N1 pandemic starting in subsequent years.

There is not much the public can do at this time about H5N1 — with the exception of not touching dead or dying birds — but public health authorities and policymakers have several options:

5. Invest more in overall pandemic prevention to protect us against not only H5N1 but also all other pandemic threats

Finally, forecasting sites like Metaculus and GoodJudgment.io can help us keep track of how the probability of H5N1 being declared a public health emergency, and how it will evolve over the coming weeks and months.

The above decomposition process results in an overall chance of 4% for the H5N1% pandemic to start in the next year, with an impact that is at least similar to COVID-19. Since the total harms of COVID-19 to the U. S. are roughly $16 trillion, the anticipated cost of H5N1 is at least $640 billion, if not much more given the likely much higher death rate compared to COVID-19. Even though proper preparation would cost far less than $640 billion, we are hardly making any effort to prepare for this expensive possibility. Since the annualized risk for every year in the future is not included in our analysis, we are estimating the value of averting an H5N1 pandemic extremely conservatively.

There is a 90% probability that sustained transmission of any kind among non-human mammals has already happened or will happen shortly.

The US is well-stocked with antivirals that may be used to treat infections in humans as well as vaccinations that are tailored to the strain of bird flu that is currently circulating. Additionally, sample or “seed” strains of the virus are available from the US Centers for Disease Control and Prevention (CDC), which could be used by manufacturers to create more vaccines.

Two confirmed cases of avian influenza, also referred to as bird flu, being transmitted to humans have been reported in the US since 2022. One noteworthy instance involved a Texas-based farm worker who showed conjunctivitis and other symptoms suggestive of exposure to bird flu. Various media outlets report that people who are frequently exposed to domestic or wild birds have died from avian influenza.

The H5N1 strain, which is currently causing the cases that have been reported, is not yet virulent enough to allow for widespread human transmission. However, scientists are still keeping a close eye on its possible evolutionary path, which might greatly increase its ability to spread among humans and raise the risk of a global pandemic.

“We are not really talking about a virus that is yet to make a jump, we are talking about a virus that is globally present, already infecting a range of mammals, and is circulating,” Dr. Suresh Kuchipudi, a bird flu researcher in Pittsburgh, told Daily Mail. He continued by saying that it’s imperative that people get ready.

FAQ

How bad is the bird flu epidemic?

So far, current H5N1 bird flu viruses lack changes seen in the past that have been associated with viruses spreading easily among poultry, infecting people more easily, and causing severe illness in people. Since December 2021, 11 human cases of H5N1 have been reported globally.

Is the bird flu the same as the regular flu?

Avian flu and pandemic flu are not the same thing. Avian influenza, or “bird flu”, is a virus that affects birds. Pandemic flu is human flu that would affect millions of people all around the world. Very rarely, an avian flu virus will infect a person.

Can bird flu spread to humans?

Scientists know that bird flu can spread to humans when they come into contact with infected animals, including dead ones, without wearing protective gear, which seems to have been the case with a person recently infected in Texas.

How many people have died from bird flu?

In the past two decades, nearly 900 people have been diagnosed globally with bird flu and more than 460 people have died, according to the World Health Organization. There have been only two cases in the U.S., and neither were fatal.