Avian Flu

Subject : Science and technology

Section :Health

Concept :

The ongoing avian flu outbreak is considered the largest observed in Europe to date, according to the European Food Safety Authority, an EU agency. Between October 2021 and September 2022, 50 million farm birds had to be culled in 37 countries
Tests revealed that the highly pathogenic avian flu virus H5N1 was the culprit.
To stop the spread of the dangerous pathogen, more than 50,000 mink on the farm were killed.

Avian Influenza

A disease caused by avian influenza (AI) Type A viruses found naturally in wild birds worldwide.
AI viruses are broadly classified as low pathogenic AI (LPAI) and highly pathogenic AI (HPAI) viruses, based on their pathogenicity.
The two virus types identified so far in the outbreaks H5N1 and H5N8 come under the category of Highly Pathogenic Avian Influenza (HPAI), which is of major concern to those keeping birds, because it leads to disease and death of fowl and causes economic havoc. H5N1 is a known threat to humans as well.
The virus can infect domestic poultry including chickens, ducks, turkeys and there have been reports of H5N1 infection among pigs, cats, and even tigers in Thailand zoos.
There is no vaccine against H5N1.
Most avian influenza viruses do not infect humans, however some, such as A(H5N1) and A(H7N9), cross the species barrier and cause disease or subclinical infections in humans and other mammals as well.
The Avian (H5N1) virus subtype, a highly pathogenic virus, first infected humans in 1997 during a poultry epidemic outbreak in Hong Kong SAR, China.

Types of Influenza Virus

There are four types of influenza viruses: influenza A, B, C, and D.
Influenza A and B are the two types of influenza that cause epidemic seasonal infections nearly every year.
Avian influenza belongs to Type A viruses
Type A viruses are classified based on two proteins on their surfaces – Hemagglutinin (HA) and Neuraminidase (NA).
There are about 18 HA subtypes and 11 NA subtypes.
Several combinations of these two proteins are possible e.g., H5N1, H7N2, H9N6, H17N10, H18N11 etc.
Influenza C mainly occurs in humans, but has been known to also occur in dogs and pigs.
Influenza D is found mainly in cattle. It’s not known to infect or cause illness in humans yet.

How Does it Spread to Humans?

Several subtypes and strains of avian influenza viruses are now found around the world, some of them capable of causing death among humans and others inflicting serious losses on poultry farmers.
Though Human to Human transmission — which takes place mostly after intimate and constant physical contact — is rare, the infection is virulent and, in an estimated 60% of cases, fatal.
There are no known instances of the flu spreading through ingestion of the bird, even though people do contract it while plucking or culling an infected bird without proper protection, or if they are in a water body that has the droppings of an infected bird.
In humans, the symptoms of bird infection are the same as that of any other seasonal flu — fever, body ache, sore throat, runny nose, headache, fatigue, etc., however, it can turn serious very quickly, and lead to respiratory distress.

Why is the mink farm outbreak is concerning?

While there have been some cases of H5N1 infecting humans, the World Health Organization has said there’s no evidence of human-to-human transmission so far.
When the disease has spread to humans and other mammals, it has been via direct contact with excrement from infected birds or their carcasses.
But the mink outbreak appears to be a rare case where mammals are transmitting the disease to each other rather than through direct contact with an infected bird.