Frequently asked questions on bird flu .
Sydney Morning Herald -- October 16, 2005
WHAT IS BIRD FLU?
Bird flu is also called avian influenza. There are 15 strains of flu that affect birds, but the one causing the amplifying global scare is the H5N1 subtype. It has circulated in migrating wild birds for years and has spread to poultry flocks, starting in South-East Asia, spreading to Russia and now reaching Turkey. It is highly lethal to domesticated birds.
HOW DOES IT SPREAD TO HUMANS?
Avian flu was first identified in Italy around a century ago. It was not thought to be transmissible to humans until 1997, when the first human cases were seen in Hong Kong, also involving H5N1. In the latest outbreak, about 60 people in Asia have died, amounting to roughly half the known number of infections, which is a very high fatality rate. Almost all these casualties were directly exposed to infected fowl, making contact with the virus through the birds' saliva, nasal secretions and faeces, which become dry, pulverised and are then inhaled. Avian flu is not a food-borne virus, so the risk from eating properly cooked chicken is negligible.
SYMPTOMS:
Bird flu in humans causes symptoms that are like human flu, such as fever, cough, sore throat and muscle aches, conjunctivitis, pneumonia and other severe respiratory diseases.
THE RISK:
At present, H5N1 is not easily transmitted from bird to human. In other words, a person would have to pick up a lot of the virus to be infected.
Nor is it easily passed from human to human: there have been only three suspected cases, in Thailand, Hong Kong and Vietnam, where this is believed to have happened.
THE CONCERN:
The big worry is that H5N1 could pick up genes from conventional human flu viruses, making it both highly lethal and highly infectious. Because it would be a radically new pathogen, no one would have any immunity to it. The mutation could occur if H5N1 co-infects a human who already has ordinary flu or the agent is picked up from poultry by an animal such as a pig that can carry bird and regular flu strains.
PAST PANDEMICS:
In the 20th century, there have been three flu pandemics, in 1918-19, 1957-58 and 1968-69. The worst of all was the 1918-19 pandemic, which killed as many as 50 million people - more than the death toll from AIDS in more than two decades. The latest research suggests that the so-called Spanish flu virus was itself a bird flu virus that leapt the species barrier to humans.
THE FUTURE:
The World Health Organisation (WHO) says the next pandemic is simply a matter of time. Jet travel and the world's huge population today mean the toll from Spanish flu could easily be surpassed.
VETERINARY CONTROLS:
These are the time-honoured first line of defence in any outbreak of animal disease. The task is to identify farms where there is an outbreak of H5N1, quarantine the area, kill all fowl suspected to be in contact with it, disinfect machinery, vehicles and clothing, and ban sales of poultry products from the affected region. But these controls are only really dependable if a country has a good surveillance network and responds quickly and effectively to an outbreak. One vital tool is compensation: without some reimbursement, farmers may be loath to report flu among their flock and be tempted to sell diseased birds, thus amplifying the epidemic.
HUMAN PREPAREDNESS:
Countries are being urged to stockpile antiviral drugs, boost surveillance and response systems and prepare for the swift manufacture and distribution of an effective vaccine, for when it becomes available. Some authorities are encouraging vaccination against conventional flu strains for people who could be exposed to bird flu, in order to decrease the risk of co-infection. On the international front, the WHO is striving to improve the sharing of information and virus samples - vital in the search for vaccines and treatment - and is co-ordinating closely with other agencies responsible for food safety and animal health.
VACCINE:
No definitive vaccine against the viral threat is available, because no one knows the precise shape that it will take after mutating to the feared highly contagious form. Several prototypes are being explored, but the risk is that they could be only partially effective or even useless because the virus's genetic shape will have changed and will not be recognised by antibodies. If a pandemic does occur, one worry is about manufacturing capacity and distribution: making enough of the vaccine and getting it on time and to the right people, without causing panic or a black market or leaving poor countries helpless.
DRUGS:
The range of antiviral drugs is small, but especially so when it comes to bird flu. Four antiviral medications are commonly prescribed for the A category of influenza viruses of which H5N1 is a subgroup. Two of them, amantadine and rimantadine, are ineffective against H5N1. The other two are zanamavir (commercialised as Relenza) and the widely-stockpiled oseltamivir, commercialised as Tamiflu. These medications are called neuraminidase inhibitors, which block the virus from replicating. If taken within a couple of days of the onset of illness, they can ease the severity of some symptoms and reduce the duration of sickness. According to the US Centres for Disease Control and Prevention, the two drugs "would probably work" against H5N1 infection, but more work is needed to confirm this.
Sources: WHO, CDC, US National Institute of Health and Infectious Diseases (NIAID), World Organisation for Animal Health (OIE).
AFP
Tejek: Be sure to update your Cousin so he won't be passing out misinformation to additional people. |
