Avian Influenza

Overview

Avian influenza is a viral infection that affects birds primarily, and humans as they come in direct contact with the infected bird or its body fluids. There are two main types of bird flu, including low pathogenicity avian influenza (LPAI) and highly pathogenic avian influenza (HPAI).
The most common subtypes that affect humans are H5N1, H7N9 and H9N2. Early diagnosis, immediate medical care and preventive measures ensure public health protection.

What is Avian Influenza?

Avian Influenza, or bird flu, is a highly contagious viral infection that primarily affects birds. Humans are also affected by this disease through direct contact with the infected birds or their secretions. While human cases are rare, they can prove to be potentially fatal.

What are the Types of Avian Influenza?

Influenza A viruses cause avian influenza in birds. These viruses are grouped into two main categories based on how they cause disease in poultry:

Low Pathogenicity Avian Influenza (LPAI)

Infection with LPAI viruses shows either no signs of disease or respiratory signs such as nasal discharge, sneezing, coughing and swollen infraorbital sinuses in poultry. Other common signs also include ruffled feathers or a dip in egg production. In infected wild birds, low pathogenicity avian influenza A viruses cause few signs of infection, increasing the chances of mutation into highly pathogenic avian influenza viruses.

Highly Pathogenic Avian Influenza (HPAI)

Certain avian influenza viruses, such as A(H5) and A(H7), are classified as HPAI A viruses, causing fatal disease and high mortality in infected birds and poultry. These viral infections damage several internal organs, increasing the mortality rate up to 90% to 100% in chickens. These viruses also transfer into wild birds, causing a geographic infection spread among migrating birds.

Avian influenza A viruses are further divided into subtypes based on two proteins found on the surface of the virus, including hemagglutinin (HA) and neuraminidase (NA). H5, H6, H7, H9 and H10 viruses are common to cause infections in humans, specifically A(H5N1), A(H7N9) and A(H9N2).

Here are the main types of avian influenza that affect humans:

H5N1
First identified in 1959 in Scotland, this highly pathogenic avian influenza A virus is one of the most dangerous subtypes that affect both birds and humans. It causes major outbreaks in poetry and transmits to humans causing severe illness or death through direct contact with the infected or contaminated environments.

H7N9
A low pathogenicity avian influenza A virus that has been primarily detected in birds in the past. In China in 2013, this infection was reported to raise concerns about a potential pandemic spread among both humans and birds. This infection is caused by direct exposure to infected poultry, especially in live poultry markets. It causes signs of severe respiratory illness in humans, with an increased mortality rate.

H9N2
Found in Hong Kong and nearby mainland China in 1988, this LPAI virus is widespread in poultry and also affects humans. Researchers consider it fatal as it can reassort with other viruses and create new, more dangerous strains. It causes mild signs of the disease, such as conjunctivitis, muscle aches, sore throat and fever. In serious cases, it leads to acute respiratory diseases and pneumonia.

Transmission of Avian Influenza

One cannot be infected by consuming properly cooked eggs or poultry. Hence, humans can be infected by the virus in the following ways:

• In direct contact with the infected animal's faeces or saliva
• Living in contaminated areas
• Getting the animal's body fluid into the eyes, nose or mouth after touching them

Symptoms of Avian Influenza

Following are some of the common avian influenza symptoms in humans:

• Conjunctivitis
• Fever
• Runny or stuffy nose
• Sinusitis
• Muscle ache
• Cough
• Fatigue
• Sore throat
• Shortness of breath
• Vomiting and nausea
• Diarrhoea

Causes and Risk Factors of Avian Influenza

Bird flu is caused by influenza A viruses, with H5N1 being most common among humans. It affects your lungs and upper respiratory tract, causing life-threatening complications.

The risk of avian influenza outbreaks and transmission can increase because of the following reasons:

- Contact with Infected Birds: Coming in direct contact with wild birds or poultry increases the risk factor. This includes touching the infected birds, their secretions or contaminated materials.

- Poor Biosecurity Measures: Lack of disinfection, inadequate ventilation and poor hygiene in poultry farms can cause the virus to spread.

- Wild Bird Migration: The virus is spread across new areas when infected wild birds migrate.

- Environmental Factors: Poor nutrition, stress and overcrowding can make birds more susceptible to infection.

Diagnosis of Avian Influenza

Here are the common ways of diagnosing bird flu in humans:

• Upper Respiratory Tract Samples: A sample from your nose and throat is taken using a swab and is studied to detect the traces of the viruses.
• Eye Samples: If you have conjunctivitis, the doctor may collect a sample of fluid from the eye and conduct various tests.
• Sputum Samples: A sample of phlegm is tested, if the infected individual is coughing excessively.

Avian Influenza Treatment

The viral infection increases mortality in humans. Taking certain antiviral medications can help treat the infection, these include:

• Oseltamivir (Tamiflu®)
• Zanamivir (Relenza®)
• Peramivir (Rapivab®)

Complications of Avian Influenza

Avian influenza can cause severe complications including respiratory diseases in humans. These include the following:

• Sepsis
• Pneumonia
• Respiratory failure
• Bacterial infections
• Acute respiratory diseases, such as acute pharyngitis
• Meningoencephalitis

Preventive Measures for Avian Influenza

Following are the ways to prevent avian influenza from spreading:

• Wear gloves and masks when you work with livestock, birds and wild animals
• Wash hands with soap and water if dealing with animals, or being in contaminated areas
• Do not work with animals and birds exposed to the flu
• Avoid wearing shoes at home after being in contaminated environments

Myths and Facts Related to Avian Influenza

Following are some myths and facts associated with avian influenza:

Myth 1: Avian influenza is only a problem for the poultry
Fact: Avian influenza also affects wild birds and humans when they come in contact with infected birds or contaminated areas.

Myth 2: Avian influenza is highly contagious
Fact: It cannot spread from one person to another. It only spreads through direct contact settings.

Myth 3: There is no treatment for Avian influenza
Fact: Taking antiviral medications and following hygiene practices help reduce the severity of the illness.