‘Wise to assume bird flu pandemic will cause more severe disease in humans than COVID-19’

Subject: Science and tech

Section: Health

Context:

H5N1, also known as bird flu, has been recognized as a potential public health threat for two decades, highlighted by recent cases in the United States.

Details:

In 2022, the first human infection in the U.S. occurred, and in April, a man in Texas contracted the virus from cows, raising global health concerns.
Although primarily affecting birds, H5N1’s ability to infect mammals indicates its increasing adaptability, with growing concerns about the potential for human-to-human transmission.

The H5N1 strain of bird flu viruses, first identified in a goose in China in 1996, has undergone significant evolution, spreading globally and generating multiple subtypes.
The latest subtype, known as H5N1 virus clade 2.3.4.4b, emerged in Europe in late 2020 and has since caused widespread outbreaks across multiple continents, affecting both avian and mammalian species, including minks and sea mammals.
A notable recent development is the transmission of this clade to cattle in the United States, which has led to a confirmed case of cow-to-human infection.
At present, no case of human-to-human transmission of bird flu has been found.

Issue with the new subtype:

The current subtype of the bird flu virus has demonstrated a concerning capability to infect a broader range of wild birds and mammals.
- As the virus spreads among various hosts, it increases the chances of genetic mutations, thereby heightening the risk of viral evolution and its potential adaptation to mammals.
The global distribution of H5N1 viruses primarily affects poultry, making them panzootic among birds. However, the concern arises from their potential to transition into a human virus, potentially triggering a human pandemic.

Avian influenza (AI)

Avian influenza (AI) is a highly contagious viral disease affecting several species of food-producing birds (chickens, turkeys, quails, guinea fowl, etc.), as well as pet birds and wild birds.
Occasionally mammals, including humans, may contract avian influenza.
Influenza A viruses are classified into subtypes based on two surface proteins, Hemagglutinin (HA) and Neuraminidase (NA). For example, a virus that has an HA 7 protein and NA 9 protein is designated as subtype H7N9.
Avian influenza virus subtypes include A(H5N1), A(H7N9), and A(H9N2).
- HPAI A(H5N1) virus occurs mainly in birds and is highly contagious among them.
- HPAI Asian H5N1 is especially deadly for poultry.
Prevention: Strict biosecurity measures and good hygiene are essential in protecting against disease outbreaks.
Eradication: If the infection is detected in animals, a policy of culling infected and contact animals is normally used in an effort to rapidly contain, control and eradicate the disease.

Highly Pathogenic Avian Influenza (HPAI):

The two virus types identified so far in the outbreaks — H5N1 and H5N8come 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
Out of the three types of influenza viruses (A, B, and C), influenza A virus is a zoonotic infection with a natural reservoir almost entirely in birds. Avian influenza, for most purposes, refers to the influenza A virus.
Though influenza A is adapted to birds, it can also stably adapt and sustain person-to-person transmission.

Mode of transmission:

Avian influenza is most often spread by contact between infected and healthy birds, though can also be spread indirectly through contaminated equipment.
The virus is found in secretions from the nostrils, mouth, and eyes of infected birds as well as their droppings.
HPAI infection is spread to people often through direct contact with infected poultry, such as during slaughter or plucking.

Is this influenza airborne?

Though the virus can spread through airborne secretions, the disease itself is not an airborne disease.

Human to human transmission:

In its present form, human-to-human infection is not known — human infections have been reported only among people who have handled infected birds or carcasse

Source: DTE