What Is Avian Flu? What Is Bird Flu?

Editor's Choice
Main Category: Bird Flu / Avian Flu
Also Included In: Flu / Cold / SARS;  Infectious Diseases / Bacteria / Viruses
Article Date: 04 Mar 2012 - 0:00 PST


Avian flu, also known as bird flu and more formally as avian influenza, refers to flu caused by viruses that infect birds and make them ill. It is an infectious disease of birds caused by type A strains of the influenza virus. HPAI (highly pathogenic avian influenza) - the more virulent one - is the one health care authorities are most concerned about. Avian flu affects several types of birds, including farmed poultry, i.e. chickens, geese, turkeys and ducks.

Avian flu is the illness caused by the Avian influenza virus.

Bird flu can be transmitted from livestock to wild birds and also to pet birds, and vice-versa. The virus spreads through infected birds, via their saliva, nasal secretions, feces, and feed.

Birds become infected when they are in contact with contaminated excrements or secretions, or tainted surfaces. Domesticated poultry becomes infected via direct contact with infected waterfowl, other infected livestock, or tainted surfaces of cages and other farming equipment and installations.

There have been several bird flu outbreaks since the first one in December 2003 - wild birds and farmed livestock have died because of bird flu in Africa, Asia and Europe.

According to Medilexicon's medical dictionary, Avian Influenza is:

"A serious viral disease of many birds, both domestic (especially chickens, ducks, and turkeys) and wild. Wild birds act as reservoirs for influenza A virus (Orthomyxovirus); in birds, these viruses are responsible for clinical pictures ranging from low-grade illness to serious outbreaks with high mortality rates; signs range from reduced egg production to a fulminant peracute clinical course; respiratory signs (sinusitis, blood-stained nasal discharge) often occur in acute infections.

Historically, close contact of fowl with humans has been shown epidemiologically to foster cross-species jump (avian to human) of new influenza strains (e.g., Hong Kong 1997 [AH5N1], Hong Kong 1999 [AH9N2]). New neuroaminidase and hemagglutinin subtypes develop as a result of antigenic drift, and less commonly, antigenic shift resulting in serious human influenza epidemics, and give rise to the need for annual reformulation of flu vaccines to protect against newer active strains. Currently 15 hemagglutinin and 9 neuraminidase subtypes have been identified in reservoir species."

There are 16 different avian flu types. The H5N1 strain is the one that causes the most concern, because it is the most virulent; the deadliest. Fortunately, humans do not become easily infected with the H5N1 virus strain. However, some highly pathogenic strains have caused severe respiratory diseases in humans. In the vast majority of cases of human infections, there was contact with infected poultry or objects/surfaces contaminated with their feces or secretions.

Experts are worried that the virus could one day mutate and become easily-human-transmissible. If this occurred, a serious influenza pandemic could occur.



Dark red represents countries with humans, poultry and wild birds killed by H5N1. Normal red represents countries with poultry or wild birds killed by H5N1. Source: WHO

What are the signs and symptoms of avian flu?

What is the difference between a sign and a symptom? A symptom is something the patient feels and describes, such as a headache or dizziness, while a sign is something other people can detect, such as a rash or a swelling.

In a large number of patients, flu caused by the H5N1 virus develops unusually aggressively. Bird flu's incubation period of two to eight days is longer than for normal, human seasonal flu (two to three days). In some cases, the incubation period may take as long as 17 days.

For field investigations and monitoring of patient contacts, WHO (World Health Organization) recommends health care professionals use an incubation period of seven days.

Humans with avian flu may have the following signs and symptoms (many are the same as normal seasonal human flu):

• A cough, usually dry
• A high fever, over 38C
• Aching bones, joints and muscles
• Bleeding from the nose
• Blocked nose
• Chest pain
• Cold sweats and chills
• Fatigue
• Headache
• Loss of appetite
• Runny nose
• Sleeping difficulties
• Stomach upset, sometimes diarrhea
• Bleeding from the gums
• Some patients develop the symptoms of lower respiratory tract infection, which includes breathing difficulties. This occurs around day five of the first symptoms
• Hoarse voice
• Sputum is sometimes bloody

Patients with avian influenza can deteriorate rapidly, resulting in pneumonia, multiple organ failure, and death.

What are the causes of avian flu?

Humans can become infected and ill with avian influenza after coming into contact with infected birds. The following circumstances have been linked to human illness:

• Touching infected birds
• De-feathering infected birds
• Touching secretions from infected birds (saliva or fluids from infected birds)
• Being in contact with the feces of infected birds
• Inhaling dried feces dust from infected birds
• Preparing poultry for cooking, if the bird was infected. This also includes household settings
• Slaughtering or butchering infected poultry
• Markets where live birds are sold. If the birds are infected, those who handle them have a risk of becoming ill

You cannot become infected if you eat cooked poultry. WHO and several national health authorities in Europe say poultry should be cooked to at least an internal temperature of 74 C (165 F). According to experts, humans cannot become infected by eating eggs. Even so, the US FDA (Food and Drug Administration) says eggs should be cooked until both the white and yolk are firm.

Feces of infected birds contain the bird flu virus. Bird droppings can contaminate feed, equipment, vehicles, shoes, clothing, soil, dust and water. The feet and bodies of animals can also carry the H5N1 virus.

WHO says that controlling H5N1 virus circulation in poultry is vital to reduce the risk of humans becoming infected. Sometimes the H5N1 virus is persistent, and is hard to get rid of in poultry populations. WHO says countries, their agricultural and health authorities, as well as farmers and poultry traders must be committed to the long-term control of bird flu - this involves close liaison between them.

Diagnosing bird flu

A doctor will be able to diagnose flu according to its hallmark signs and symptoms. The patient will also be asked about any recent travel, as well as any contact with birds.

Bird flu needs to be diagnosed early on during the disease's cycle. A respiratory specimen will be collected and sent to the lab - this should ideally occur within four to five days of symptoms appearing.

Rapid Test for Avian Influenza A Virus in Humans - in 2009, the FDA approved the AVantage A/H5N1 Flu Test, which detects influenza A/HN1 (bird flu) from nose or throat swabs collected from patients with flu-like symptoms. The test takes less than 40 minutes to identify a specific protein (NS1) that indicates the presence of A/H5N21 virus subtype. The test is manufactured by Arbor Vita Corporation, California, USA.

What are the treatment options for avian influenza?

According to WHO, antiviral medications, such as oseltamivir can suppress viral replication and improve outcomes for patients, especially survival prospects. Oseltamivir should be administered within 48 hours after the onset of symptoms for best effect. However, as avian influenza mortality rates are high, doctors should consider prescribing oseltamivir for patients who were diagnosed later. For those with severe symptoms, doctors may have to increase the recommended daily dose, as well as treatment duration. Physicians should bear in mind that drug absorption may be severely impaired in patients with severe gastrointestinal symptoms.

Patients diagnosed with avian flu or who are suspected of having avian flu will be told to either remain at home or will be hospitalized (in isolation from other patients).

The National Health Service (NHS, UK) states that:

"Oseltamivir (Tamiflu) and zanamivir (Relenza) could be effective in treating influenza caused by the H5N1 bird flu virus. However, more studies are needed to demonstrate their effectiveness."

Patients should:

• Rest
• Drink lots of fluids
• Receive proper nutrition
• Receive medications for pain and fever (prescribed by a health care professional)

Complications, such as bacterial pneumonia, are common in patients infected with H5N1 virus. These will be administered antibiotics; some may need extra oxygen.

Preventing avian influenza

It is currently impossible to stop avian influenza from spreading - it is a virus that is carried by birds, including wild birds that migrate. Understanding bird migration and monitoring their movements provides local health and agricultural authorities with vital data so that they can prepare and protect livestock.

Vaccination - there are vaccinations for human seasonal flu, but not for bird flu. Various public health laboratories around the world, as well as pharmaceutical companies are working towards producing an avian flu jab.

What you can do - there are measures each individual can take to minimize the spread of flu, bird flu, and many other infections, these include:

• Hand hygiene - regularly wash your hands with warm water and soap before and after using the toilet, and before preparing meals. Wash your hands after coughing.
• If you cough, do so into the inner part of your elbow, not your hand. If you cough into your hand and then touch things, other people may become infected if they touch surfaces you contaminated. If possible, use a tissue when you cough, and dispose of it carefully.
• If you are ill, stay away from public places and avoid contact with people
• When visiting your doctor, tell the receptionist so that you can be isolated from other patients. Some GP (general practice, primary care) clinics may give you a surgical mask to wear
• Make sure you are up-to-date with your vaccinations, especially seasonal flu and pneumococcal vaccines

When preparing foods, do not use the same utensils for cooked and raw meats. Before handling raw poultry, wash your hands with soap and water before and afterwards. Cooked poultry is safe to eat.

Do not go near a dead or sick bird. Call your local authority and report any sightings of dead animals. Follow local and national guidelines if you work with domestic birds.

What do experts fear? At the moment it is very hard for a human to become infected with bird flu, and extremely rare for one human to pass avian influenza onto another human. Experts fear that if a human who is already ill with seasonal human flu becomes infected with bird flu, the H5N1 virus may exchange genetic information with the human flu virus (H1N1) and acquire its ability to spread from human-to-human. An easily human-transmissible avian flu virus strain could have devastating consequences.

Bird flu has a very high death rate, in some parts of the world over 50% of people who get ill die. If bird flu became a global pandemic, many people, possibly millions, could die.

For a human to become infected, the H5N1 virus strain needs to get deep into the lung. This feature makes it more deadly, but also makes it less transmissible. People with infection deep down in the lung have fewer viruses in their coughs and sneezes compared to those with upper respiratory tract infection.


H1N1 (seasonal human flu) infects higher up in the respiratory tract, while H5N1 infects further down, making it more lethal but less human transmissible

A mutated virus might, for example, infect the upper respiratory tract as well as deeper down - sick people's coughs and sneezes would have more viruses in them, making it easier to infect others. Those nearby would get sick more easily, because the virus would not have to go all the way down to cause illness.

Controlling bird flu outbreaks helps reduce the likelihood of a bird flu virus coming into contact with a human flu virus and mutating. Controlling seasonal human flu numbers is also important. WHO says controlling bird flu outbreaks and eliminating them as soon as possible is a top priority for public and global health.

Written by Christian Nordqvist
Original article date: 28 Jan 2004. Article updated: 4 March 2012.


Copyright: Medical News Today
Not to be reproduced without permission of Medical News Today

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