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  • April, 2023
  • Maravai LifeSciences
  • From the Science and Innovation Office

Have you tried to buy eggs recently? You might have noticed the significant price hike if you are lucky enough to find some. This critical shortage is partially caused by rising fuel and bird food costs, but the primary driver is the worst bird flu outbreak the world has ever seen.

The highly infectious H5N1 bird flu strain is responsible for the deaths of millions of domestic birds and hundreds of thousands of wild birds. But perhaps most concerningly, it is also now being found in mammals.

Bird flu, as its name suggests, is an infectious influenza disease that affects poultry and wild birds. The virus that infects birds has been circulating for over 100 years, but the H5N1 strain, the most prevalent variant now, was first reported in China in 1996.

Like all influenza outbreaks, bird flu is cyclical – becoming more prevalent in the autumn and winter before fading away in spring and summer.

The virus can spread through entire flocks of domestic birds within days, primarily transmitted through infected birds’ droppings and saliva or contaminated feed and water.

The World Organization for Animal Health (WOAH) has recorded almost 42 million individual cases in domestic and wild birds since the outbreak began in October 2021. Nearly 15 million domestic birds, including poultry, have died from the disease, and more than 193 million more have been culled. In many countries, the widespread discards of egg-laying chickens have led to egg shortages in stores – you only need to go to Costco to notice the impact!

At the moment, it’s unclear why this outbreak is so much worse than others previously. Like COVID, the virus may have mutated to enable it to spread more readily from bird to bird. However, this H5N1 strain not only spreads faster, but it also can infect mammals.

WOAH has counted 119 outbreaks of the virus amongst a spectrum of mammals, although it says this is undoubtedly an underestimate. The species that have been known to be affected include dolphins, seals, foxes, otters, grizzly bears, and mink. If you take a trip to San Diego Zoo, you’ll notice that all the penguins, as are the otters, are off-exhibit.

The route of infection for mammals may be through the infected mammal having fed dead or sick wild birds with the virus. The more worrying possibility is that the virus has mutated to infect mammals. Currently, there has been no evidence of the virus spreading between mammals.

To put this concerning possibility into context, the World Health Organization (WHO) says that over the past 20 years, 870 humans have been infected with avian flu, and 457 have died. These documented cases primarily occurred when humans came into close contact with infected birds in factory or farm settings. Another way to look at that is that avian flu has a 50% fatality rate.

The Centers for Disease Control (CDC) consider the risk to the general public low. The WHO has called for effective monitoring of the H5N1 virus to see whether it is mutating into a form that can now spread amongst humans. So, for now, let’s hope the infection rates among birds diminish in the upcoming spring… and the egg-laying chickens can rebound!