The facts about the Bird Flu

[Guest guest]

What is bird flu?

Bird flu - known technically as avian influenza - is a highly contagious viral

disease affecting mostly chickens, ducks, turkeys, quails and other birds, and

was first identified more than 100 years ago.

It can be caused by any one of about 20 different strains of the influenza

virus. The recent outbreaks in Asia, however, have been largely caused by a

highly contagious and virulent strain, known as H5N1. (The name H5N1 refers to

the specific nature of two proteins, haemagglutinin and neuraminidase, found on

the surface of the virus.)

Is bird flu a threat to humans?

The Asian bird flu outbreaks have been caused by a strain of influenza A called

H5N1. At present, H5N1 is only slightly infectious to humans and cannot be

transmitted from one human to another. However, experts fear H5N1 may evolve

into a virus that could be transferred among humans. This, they say, could lead

to the first flu pandemic of the 21st century.

According to the US Centres for Disease Control, the three great flu pandemics

of the 20th century were the result of genetic material from bird flu viruses

becoming incorporated into human flu viruses (see 'Influenza Pandemics', CDC).

This led to a far more dangerous virus, which was able to rapidly spread

worldwide.

There are two ways H5N1 could become a greater threat to human health. One is

that the genetic material of the virus could evolve, giving rise to new, more

virulent strains.

Alternatively, the virus could combine its genetic material with that from other

influenza viruses that already infect humans. The more frequently humans come in

contact with infected poultry, the more likely this is to happen.

Why are people worried about bird flu getting into pigs?

Both avian and human influenza viruses can infect certain animals, such as pigs.

This creates a genetic 'melting pot' in which viruses can swap their genes and

acquire each other's properties. For example, if a bird flu virus were to swap

genes with a human flu virus, it could acquire the capacity to infect humans,

and this could lead to human-to-human transmission. This could generate a new

virus that would pose a greater threat to human health.

Can bird flu be treated?

The bird flu virus responsible for the recent outbreaks in Asia has been found

to be resistant to the two oldest and cheapest flu drugs available, namely

rimantidine and amantidine. However, researchers with Australia's Commonwealth

Scientific and Industrial Research Organisation claim that flu drugs Relenza

(zanamivir) and Tamiflu (oseltamivir) are effective treatments against the

disease.

There is a worry, however, that antiviral drugs are expensive and in limited

supply. Ira Longini at Emory University in Atlanta, Georgia, modelled Tamiflu's

potential impact and came to this conclusion, according to a news report

published in Nature in February 2004.

In addition, a number of companies are trying to develop a vaccine against bird

flu. Such vaccines present a particular challenge, as the flu viruses against

which they are intended to provide protection (by stimulating the production of

virus-fighting antibodies) mutate frequently. As a result, any vaccine against a

flu virus needs to be modified as the virus itself evolves.

What has been done to minimise the risk of bird flu epidemics?

Culling (killing large numbers of infected and potentially infected animals) and

putting infected farms in quarantine are two common measures for limiting the

spread of bird flu. According to the World Health Organisation " most influenza

experts . agree that the prompt culling of Hong Kong's entire poultry population

in 1997 probably averted a pandemic. " (see 'Influenza pandemics: can they be

averted?' in 'Avian influenza')

A third option is vaccinating birds against the virus. This remains

controversial as an effective means of controlling the disease remains

contentious. In 1997, the Chinese government decided to vaccinate poultry in

order to limit the spread of the disease. Concerns have been raised, however,

that this decision may have in fact contributed to the spread of the disease.

Inefficient vaccines are a concern as they can allow the virus to replicate

without the animals showing any symptoms, a phenomenon known as a 'silent

epidemic'. (see 'Probe into 'botched' bird flu jabs', The Age).

In July 2004, however, Indonesia launched a poultry vaccination drive, and

Thailand is considering the same course of action.

The World Health Organisation recommends that people at high risk of being

infected by the bird flu virus - mainly those involved in culling operations -

should be vaccinated with the most recent human flu vaccine available. One

reason for doing this would be to minimise the chances of anybody being infected

by both the bird flu and human flu viruses simultaneously. Should that happen,

the two could combine their genetic material, creating a more harmful virus

capable of spreading easily through the human population.

Finally, there have been suggestions that wild migratory birds play a role in

spreading bird flu across large distances (see Bird flu 'could pose global

threat to humans'). Despite such concerns, the UN Food and Agriculture

Organisation, has recommended against culling wild bird populations, arguing

that there is insufficient evidence to support it (see Bird flu nations urged

not to cull wild birds).

What is the history of bird flu outbreaks? What is their impact on human health?

Bird flu outbreaks are not uncommon. Usually, however, they do not affect

humans.

The oldest record of a bird flu outbreak having an impact on human health was

the 1918 human flu pandemic. This, and the flu pandemics in 1957 and 1968, is

believed to have been the result of a bird flu virus combining its genetic

material with a human flu virus, thus becoming very infectious to humans.

In 1997, the direct transmission of bird flu virus (H5N1) from bird to humans

was reported for the first time. Six people died in Hong Kong after being

infected in this way.

In 1999, a different bird flu virus, identified as H9N2, infected two people in

Hong Kong. They recovered, and no additional patients were reported.

In 2003, one person died from bird flu virus H5N1 in Asia, out of two reported

infections. Both patients belonged to the same family from Hong Kong, and both

were reported to have fallen ill after visiting mainland China.

The same year an outbreak of bird flu virus H7N7 infected 80 people, in the

Netherlands, killing one. During this outbreak, there were signs of

human-to-human transmission of the disease - a rare event.

Also in 2003, a child in Hong Kong was reported infected with H9N2, but

recovered.

So far, in 2004, the World Health Organisation reports 23 human casualties of

H5N1 outbreaks in Asia. Eight of these were in Thailand and 15 in Vietnam.

Outbreaks have also been reported among poultry in Cambodia, China, Indonesia,

Japan, Laos, and South Korea, but so far none of these is reported to have

infected humans.

According to the World Health Organisation, flu pandemics can be expected to

occur three or four times every 100 years. The WHO quotes experts as agreeing,

" another influenza pandemic is inevitable and possibly imminent " . (see

'Influenza pandemics: can they be averted?' in 'Avian influenza')

What is the difference between bird flu and SARS?

Both bird flu and Severe Acute Respiratory Syndrome (SARS) are respiratory

diseases, and both have caused widespread epidemics in Asia in the last 12

months. Both diseases are also zoonoses, meaning they originate in animals but

are transferred to humans.

But while the media coverage of the bird flu and SARS epidemics has made it easy

to confuse the two, SARS and bird flu are very different. Bird flu is caused by

influenza viruses, similar to those that cause human flu. In contrast, SARS is

caused by a previously unknown type of 'coronavirus', the same family of viruses

as that which causes the common cold. Also, the SARS virus is highly dangerous

to humans, whereas at present, the bird flu viruses are not.

For more reading on this topic check out

http://www.scidev.net/ms/bird_flu/index.cfm?pageid=377

http://www.timesonline.co.uk/article/0,,13509-1823930,00.html

http://www.mydna.com/health/diseases/avian/overview/avianbirdspread.html

Hope this gets rid of some of the fears and I hope this finds you and yours

well.....Mark

[Guest guest]

>

> What is bird flu?

>

> Bird flu - known technically as avian influenza - is a highly

contagious viral disease affecting mostly chickens, ducks, turkeys,

quails and other birds, and was first identified more than 100 years

ago.

I read today that last year 4000+ doses of Tamiflu were prescribed in

August, compared to 34,000+ this year. People are trying to get the

scripts to have a safeguard because the significant small supply of

Tamiflu available. I would get it to have around if I had a way,

that's for sure.

I hope the manufacture lots more ASAP,