Why Avian Influenza or Bird Flu in Humans Is More Severe Than Other Viruses

Avian influenza, commonly known as bird flu, typically infects birds but can also infect humans. Technology Networks reported that new research led by Jason Shoemaker from the University of Pittsburgh reveals the reason behind the mechanism that makes bird flu infection more severe in humans than other influenza viruses.

Shoemaker and his team used computational modeling to understand the immune response of a human body to avian influenza. Their findings show that interferon levels may be responsible for the more severe presentation of bird flu in humans, opening doors to developing novel treatments.

(Photo : Pixabay/guvo59)
Computational Modeling Shows Why Bird Flu Infection in Humans is More Severe Than Other Influenza Viruses

Avian Influenza Infection in Humans

The Centers for Disease Control and Prevention (CDC) said that avian influenza infection in humans is rarely documented and is characterized by an illness that ranges from severe to asymptomatic or mild to severe. The infection in humans is caused by the highly pathogenic avian influenza H5N1 and H7N9 viruses, causing serious illnesses with the highest mortality.

Humans can get infected when they come into contact with infected saliva, mucous, and birds' feces, which entry points of the virus include the eyes, nose, and mouth. Inhaling the virus in the air via droplets or dust could also get humans infected. Human infections mostly occur after unprotected contact with infected birds or contaminated surfaces.

Furthermore, human-to-human transmission through close contact is rare as it has only happened to a few people. But since the virus could mutate and gain the ability to spread from person to person easily, monitoring is extremely important for public health.

In humans, signs and symptoms of avian influenza include eye redness or conjunctivitis, mild flu-like upper respiratory symptoms, pneumonia, fever, cough, sore throat, runny or stuffy nose, muscle or body aches, headaches, fatigue, and difficulty in breathing. Symptoms may be severe, some may be asymptomatic, and fever may not always present.

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Avian Influenza Causes Severe Illness in Humans

The new research titled "Mathematical Modeling Finds Disparate Interferon Production Rates Drive Strain-Specific Immunodynamics during Deadly Influenza Infection," published in the journal Viruses, used computational modeling to understand the immune response of the body to avian influenza so scientists could find a better way to help.

The team used the data from mice infected with either the avian influenza H5N1 or low-pathogenic swine flu H1N1 viruses and then used an engineering-based approach to model and predict virus replication, and immune response, and levels of interferon in mice during the infection, Science Daily reported.

They determined that the production rate of interferon causes the strain-specific immune responses to be severe in the mice. That means a high viral load of H5N1 and resulting lung interferon production is the main reason for differing infection outcomes.

Shoemaker noted that their findings prove that the high-pathogenic H5N1 strain induces interferon earlier and more severe than other influenza viruses. This explains the immune response commonly observed in H5N1 infections in humans.

Although SARS-CoV-2 is not included in the study, the team wrote that their findings open a path to developing better treatments and reveal other factors that may be at play during avian influenza infection.