Poultry’s high viral transmissibility

The world loves poultry. The total number of chickens around the world is over 34 billion; 9 billion are in the United States alone. Americans eat about 118 pounds of chicken and turkey per year. And, they are easy to grow. Their feed conversion rate is low: two pounds of chicken feed contribute to one pound of growth. This is compared to beef which has an eight-to-one ratio and fish which is one-to-one.

Chickens typically live in very close proximity to each other, making infectious diseases like Avian Influenza challenging to contain. The term ‘fowl plague’ virus was first detected in 1878 in Italy. Since then, it has morphed into two categories: high and low pathogenic. This latest outbreak seems to be high. The current virus, H5N1, originated in China and then spread through Europe and the rest of Asia.

The most recent H5N1 bird flu outbreak has killed over 140 million domestic birds around the world.  In the United States alone, at least 58 million birds have either died or been culled because of Avian Influenza since January 2022.  While it is hard to tell exactly how many wild birds have Avian Influenza, the CDC estimates it is around 6,000 and is in 47 states.

Here are the U.S. counties that have reported an outbreak, to date:

Since the outbreak in 2014-2015 poultry farms have been diligent about keeping their operations sanitary and not spreading germs between facilities. The U.S. Department of Agriculture has biosecurity measures called ‘defend the flock’ and these precautions are taken seriously. An outbreak at a farm seems to be caused by wild birds that somehow infect the domestic birds.

Free-range birds are the most at risk because they can catch it from wild birds since their living arrangements are the least controlled.

And the birds that it affects are mostly egg-laying chickens versus broilers – those that we eat.  Turkeys are also affected.

Can wild birds pass it to mammals?

The World Health Organization reported to the BBC that the most recent outbreak is spilling over into mammals. It has been found in animals that eat birds such as foxes, mink, and seals. But surprisingly, dolphins, too – which generally don’t eat wild birds.

Sea lions in Peru were particularly hard hit. It is difficult to tell whether they transmitted it among themselves or they were all eating infected birds. Researcher Victor Gamarra-Toledo and his team at Peru’s Natural History Museum of the National University of San Agustín de Arequipa reported that 3,000 sea lions died. They are in the process of genetic testing to investigate the virus sequencing.

Along the coast of Maine it was reported that there have been 337 seals that are either sick or dead with H5N1 since June 2022. This has been deemed an ‘unusual mortality event along the Maine coast’ by the National Oceanic and Atmospheric Administration.

Minks at a farm in Spain were decimated this past October from an H5N1 outbreak. All 51,00 minks either died from the disease or were culled. The minks were kept in netting cages where they had a roof but the sides were open. There were sick birds found along the coast nearby.

There was also a mink farm outbreak in the Netherlands. So far none of the workers at either farm have caught the H5N1 virus and they are all wearing masks and protective clothing to mitigate their chances.

Does this spread to humans?

JAMA Network states that only a handful of human infections have been reported, all among people who have had direct contact with poultry.

An 11-year-old girl in Cambodia died from H5N1. Her family had 22 chickens and ducks so she easily could have got it by close proximity to their feces. It can be inadvertently transmitted by inhalation. While her father has the same strain of flu, it is hard to know whether he got it from the birds – or from his daughter.

In April 2022, a man in Colorado was culling an infected herd and caught it. He recovered fairly quickly as he was given Tamiflu. According to WHO, in the past nine years, from June 2003 to February 2023 there have been 870 cases of humans getting H5N1 – however, they have all had close proximity to poultry and did not catch it from another human.

Can we safely eat poultry and eggs?

It is safe to eat poultry and eggs and like any animal products, it is important to cook thoroughly.

• Properly cooked poultry and eggs (at 165 internal temp or higher) are safe to eat- and there is no evidence that it can be spread to humans through properly prepared foods
• It is unlikely that infected eggs or chickens can enter the food chain given that the symptoms of this flu have a rapid onset
• USDA has safeguards in place including testing flocks and Federal inspection programs like HPAI-risk based classification system to determine the order in which egg farms are inspected, works with the State Animal Health Officials on farm checks and testing