Bird flu (more correctly known as avian influenza) is a virus. Viruses are not animals or plants or bacteria. Strictly speaking they are not even organisms. The bird flu virus consists of three main parts: RNA (ribonucleic acid) and two types of proteins. Together, these three 'ingredients' can break into healthy body cells, infect the cell, and set free new virus particles that can continue to spread the attack.

The H and the N stand for the two proteins (haemagglutinin and neuraminidase). There are 15 known types of 'H' and 9 types of 'N' — hence the number after the letter. The current avian influenza comprises types 5 and 1 of H and N protein respectively. The Spanish Flu of 1918 which killed a lot of people, was H1N1.

At the moment, the bird flu seems to be just that: an influenza that affects birds.

It is believed that those few humans who have been infected have got the flu through direct contact with fowl.

However, sometimes an influenza virus can 'reassign' itself so that it can spread from bird to human through other animals (such as pigs), or even from human to human. If this happens, the disease can hypothetically become a pandemic.

The virus is present in just about every part of the bird: in the flesh, in the gut, in the blood, in the feathers. Birds' eggs can also carry the virus, and it is especially common in the faeces of the bird. A single gram of bird faeces can contain enough virus to kill a million birds at least.

Proper cooking destroys the virus. It seems that the real risk is in swallowing or inhaling or direct skin contact with contaminated birds, blood, entrails, feathers and excrement.

Poultry companies insist that there is no such threat. No avian influenza has been found in any commercial operations.

Should nevertheless such a risk develop, there are many workers who come in close contact with birds; not just people who work with breeding, rearing and slaughtering birds, but also mechanics, cleaners and packers. There are also people at the other end of the poultry distribution chain: cooks, chefs, food handlers and other kitchen workers. It is worth remembering that while the virus is destroyed by cooking, it is not greatly affected by freezing.

Naturally, people involved in the culling of INFECTED birds must take special precautions. This goes for workers who are likely to come in contact with contaminated faeces during clean-up operations and decontamination of poultry houses etc.

Safely ensconced in manure, the virus can survive for over a month at cool temperatures — some sources say over three months.

Should avian influenza happen to be found in, say, a commercial operation, many state and federal authorities have issued recommendations regarding the use of personal protection where there is a risk of exposure to potentially infected birds.

By and large, the recommendations concur: comprehensive skin and respiratory protection must be worn.

Appropriate gloves, boots, goggles, and overalls or a protective suit.

Keep in mind that proper decontamination of these items after work is just as important as wearing them during work. No matter how efficient the protective clothing is, TAKING IT OFF can present the greatest risk. Decontamination equipment and proper training must be in place to ensure that the protective clothing can be removed safely.

Viruses are particles. They can be stopped by an appropriate particle filter.

Most government authorities recommend at least an N95 class respirator (P2) that also must pass individual fit testing.

In S.E.A.'s opinion, this advice is somewhat puzzling, for several reasons:

• Many N95 (P2) respirators are of the 'filtering face piece' type (see picture above). It is doubtful whether such a face piece can be fit tested with any degree of accuracy.
• In standards testing, an N95 (class P2) respirator is allowed to leak up to 5%. Whether five precent leakage is an 'accpetable risk' when it comes to a deadly virus is debatable.
• Viruses are extremely small particles. The avian influenza virus is about 0.1 micrometre in diameter. When it is being carried in dust or spray, the particle size ranges from about 1 to 10 micrometres. It is unclear whether an N95 class mask can be used with confidence against such small particles.
• N95 (P2) filters are often of the electrostatic type. This means that the efficiency of the filter is significantly affected by temperature, humidity, water spray and oil mist. In a poultry-house with suspected influenza-sick birds, the workplace is likely to be hot, humid and wet from decontamination and cleaning.

SKIN PROTECTION: For most work with suspected birds, a body-covering, water-resistant suit may be sufficient, along with gloves and boots.

BREATHING PROTECTION: A tight-fitting, facial-seal rubber respirator — either a full face mask or a half mask if the suit has a visor. The respirator should be fitted with a high-efficiency, mechanical, hydrophobic (water-resistant) filter. These filters have a proven leakage of 0.003% as compared with N95 filters that are permitted to leak up to 5%. Also, a mechanical filter is far less susceptible to water spray, humidity, heat and oil mist from machinery. (For full product information, click on pictures.)

Half mask

Full face mask

High-efficiency particle filter

For extremely hazardous work (for instance, exposure to infected manure), we would rather be safe than sorry, and opt for a positive-pressure respirator and an encapsulated, pressurised suit.

Positive pressure respirator

Pressurised polypropylene suit

Sources:

Animal Health Australia 2005, Disease strategy: Avian influenza, (Version 3.1), Australian Veterinary Emergency Plan (AUSVETPLAN), 3rd edn, Primary Industries Ministerial Council, Canberra, ACT, viewed 28 Oct 2005, <http://www.animalhealthaustralia.com.au/aahc/index.cfm>

Appenzeller, T 2005, ‘Tracking the next killer flu’, National Geographic Magazine, October, pp. 4–31

Banham, C & Pollard, R 2005, ‘Revealed: bird flu battle plan’, The Sydney Morning Herald, 22-23 Oct, p. 1

Ingham Enterprises 2005, Avian Influenza, press release, viewed 28 Oct 2005, <http://www.inghams.com.au/consumer/media/Avian_Flu.PDF>

International Food Safety Authorities Network (INFOSAN) 2004, [part of WHO], 'Highly Pathogenic Avian Influenza H5N1 outbreaks in poultry and in humans: Food safety implications', Information Note No. 2/04 - Avian Influenza, viewed 28 Oct 2005, <http://www.who.int/foodsafety/fs_management/infosan/en/>

Mackenzie, D 2005, ‘Race is on to make bird flu drugs’, New Scientist, no. 2522, 22 Oct.

National Pests and Disease Outbreaks 2005, ‘Avian Influenza (Bird Flu)’, National Biosecurity Manual: Contract Meat Chicken Farming, Australian Government, viewed 28 Oct 2005, <http://www.outbreak.gov.au/response/AI/cr_avianflu.htm>

Queensland Department of Primary Industries and Fisheries 2005, Poultry: Exotic Disease Prevention, Queensland Government, viewed 28 Oct 2005, <http://www.dpi.qld.gov.au/health/5638.html>

Robotham, J 2005, ‘Facing an Invasion’, The Sydney Morning Herald, Oct. 22-23, pp. 27, 34-35

U.S. Department of Labor 2005, Guidance for Protecting Workers against Avian Flu, Occ. Safety & Health Admin., viewed 28 Oct. 2005,
<http://www.osha.gov/dsg/guidance/avian-flu.html>

Wallaart, J 2003, 'Respiratory Protection Issues in Relation to SARS (Severe Acute Respiratory Syndrome)', part of Ph.D. thesis, viewed 28 Oct . 2005, <http://www.sea.com.au/docs/articles/wallaart_sars.pdf>

Webster, RG & Walker, EJ 2004, ‘Influenza’, American Scientist, Sigma Xi — the Scientific Research Society, issue 348, pp. 122–129

World Health Organization 2005, Avian Influenza: Frequently Asked Questions, Epidemic and Pandemic Alert and Response, viewed 28 Oct. 2005, <http://www.who.int/csr/disease/avian_influenza/avian_faqs/en/index.html>