Avian influenza (Bird flu) - H5N1, H5N8, H1N1

In April, 2022 China's National Health Commission (NHC) announced that a four-year-old boy was found to have been infected with the H3N8 variant of Bird Flu after developing several symptoms, including fever.

H3N8 variant has previously been detected elsewhere in the world in horses, dogs, birds and seals.

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Bird flu, also known as Avian influenza (AI) refers to the highly contagious viral disease caused by infection with avian (bird) influenza (flu) type A viruses, such as A(H5N1) and A(H7N9).

These viruses occur naturally among wild aquatic birds (wild ducks, geese, swans, gulls, shorebirds and terns) worldwide and can infect domestic poultry (chickens, turkeys, quails, guinea fowl, etc.) and other bird and animal species.

There are four types of influenza viruses: A, B, C and D.

Influenza A virus is a zoonotic infection, meaning it can infect animals and also humans.

Influenza A viruses are divided into subtypes on the basis of two proteins on the surface of the virus: hemagglutinin (HA) and neuraminidase (NA).

There are 18 known HA subtypes and 11 known NA subtypes.

Many different combinations of HA and NA proteins are possible - H1N1, H7N2, H5N1 etc.

Influenza B virus is known only to infect humans and seals.

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.


Highly Pathogenic Avian Influenza (HPAI) A(H5N1) virus occurs mainly in birds and is highly contagious among them.

HPAI Asian H5N1 is especially deadly for poultry.

H5N1 was the first avian influenza virus to infect humans, the first infection occurred in Hong Kong in 1997.

India reported the first confirmed case of human death due to Avian influenza in July 2021.

It can lead to sepsis with shock, acute respiratory distress syndrome and even death.

Strict biosecurity measures and good hygiene are essential in protecting against disease outbreaks.

The majority of human bird flu infections have been associated with direct contact with infected live or dead poultry, though properly cooked food is considered to be safe.

The virus gets destroyed when the food is cooked at high temperature.

There is no vaccine against H5N1.

Infection in humans

Mostly, humans have only experienced infections by three different H types (H1, H2 and H3), and two different N types (N1 and N2).

Presently, two subtypes, H1N1 and H3N2, circulate among human beings, causing the seasonal flu epidemics.

Since these strains are well adapted to humans, they are referred to as human flu rather than bird flu.

Four pandemics have occurred since 1918, including the Spanish flu (H1N1), the 1957-58 Asian flu (H2N2), the 1968 Hong Kong flu (H3N2) and the 2009 swine flu (caused by a newer version of the H1N1).

Other flu A virus strains typically affect wild birds and poultry, but occasionally infect humans as well, such as the H5N1 strain which has killed hundreds of people in various countries since 1997.

But H5N1 is not known to transmit from human to human, and is primarily is a bird flu virus.

The transmission of the virus from birds to humans is rare and sustained human-to-human transmission of the H5N1 virus has not yet been established.