Is It Completely New?
- The increasing spread of highly pathogenic avian influenza (HPAI), commonly known as bird flu, to mammals is raising concerns about potential human-to-human transmission.
- As mammals, including those living in close proximity to humans, become infected, the risk of a novel avian influenza outbreak increases.
- Recently, a female sheep in northeastern Yorkshire, England, was confirmed to be infected with the H5N1 strain of highly pathogenic avian influenza.
Bird Flu Spreads to Mammals, Raising Concerns of Human Transmission
Table of Contents
Date: 2025-03-25
The increasing spread of highly pathogenic avian influenza (HPAI), commonly known as bird flu, to mammals is raising concerns about potential human-to-human transmission.
As mammals, including those living in close proximity to humans, become infected, the risk of a novel avian influenza outbreak increases.
Recently, a female sheep in northeastern Yorkshire, England, was confirmed to be infected with the H5N1 strain of highly pathogenic avian influenza.
While hundreds of cases of avian influenza have been reported in mammals worldwide, this marks the first confirmed instance of infection in sheep.
The close proximity of some mammals, such as sheep and pigs, to humans raises concerns about the potential for the virus to jump species.
According to Reuters
, pigs are particularly susceptible to acting as intermediaries in the spread of bird flu.
Pigs can be simultaneously infected with avian and human influenza viruses, potentially creating a novel influenza virus through genetic exchange, a process known as antigenic shift.
Reuters
also notes that the spread of these novel viruses to humans, who lack pre-existing immunity, could lead to widespread infection and potentially trigger a pandemic.
Data from the European Food Safety Agency and the U.S. Department of Agriculture indicates that more than 50 mammal species have been infected with avian influenza between 2016 and 2025.
These include domestic animals such as dogs, cats, cows, pigs, goats, and rabbits, and also wild animals found near human residences, including rats, raccoons, squirrels, bears, weasels, wild dogs, and badgers.
Infections have also been confirmed in a variety of other mammals, including tigers, alpacas, cheetahs, dolphins, foxes, and leopards.
The ongoing panzootic event caused by HPAI A(H5N1) virus could become one of the most vital in terms of economic losses, geographic areas affected, and numbers of species and individual animals infected.
HPAIv has been present in North America since its first detection in wild birds in November 2021. spillover into wild mammals was first confirmed at the beginning of May 2022 in Canada and then a few days later in the United States.
Bird Flu Spreads to Mammals: A Q&A on the Rising Threat
Date: 2025-03-25
The spread of avian influenza, commonly known as bird flu, to mammals is generating growing concern around the possibility of human transmission and it’s potential for a large-scale outbreak. This article provides answers to key questions about the evolving situation.
What is Bird Flu and Why Is It a Concern?
What is Bird Flu?
Bird flu, or avian influenza, is an infectious disease caused by influenza A viruses. Highly pathogenic avian influenza (HPAI), like the H5N1 strain, is particularly concerning due to its high mortality rates in birds.
Why is the spread to mammals concerning?
The increasing number of mammals infected with bird flu raises the risk of the virus adapting and spreading in new ways. This can lead to:
Increased risk of human infection: Mammals in close contact with humans can spread the virus.
Potential for genetic changes: Animals like pigs can act as intermediaries where avian and human influenza viruses can mix, resulting in a novel virus.
Which Mammal Species Have Been Affected by Bird Flu?
Which mammals are most susceptible to bird flu?
Data from the European Food Safety Agency and the U.S. Department of Agriculture show that more than 50 mammal species have been infected with avian influenza between 2016 and 2025.These include:
Domestic animals: Dogs, cats, cows, pigs, goats, rabbits.
Wild animals near human residences: Rats, raccoons, squirrels, bears, weasels, wild dogs, and badgers.
Other mammals: Tigers, alpacas, cheetahs, dolphins, foxes, and leopards.
A recent case has confirmed the first instance of bird flu in sheep.
How does Bird Flu Spread to Humans?
How can humans contract bird flu?
Humans can contract bird flu when they are exposed to fluids and secretions from infected animals.This includes:
Inhaling viral particles
Contact with saliva, mucus, or feces
Contact with milk
What is the Risk of a Bird flu Pandemic?
What are the implications of bird flu spreading among mammals?
The spread of bird flu to mammals means an increased risk of a novel virus, a virus that humans have no immunity to. According to Reuters, a novel virus could lead to widespread infection and potentially trigger a pandemic.
Key Facts About Bird Flu Outbreaks
| Aspect | Details |
| ———————– | ————————————————————————————————————————————————————— |
| Virus Strain | H5N1 is the most concerning strain. |
| Mammal Infections | Over 50 species of mammals have been infected. |
| Transmission | Primarily through contact with infected animals. |
| Pandemic Risk | The rise of highly pathogenic avian influenza is a concern with increased risk of a novel strain spreading into humans.|
| Geographic Impact | HPAIv has been present in North America since its first detection in wild birds in November 2021. spillover into wild mammals was first confirmed in May 2022 |