INDEPTH: AVIAN FLU
Avian influenza:
FAQs
CBC News Online | April 6, 2006
What are the symptoms of avian influenza, or bird flu?
 Officials collect chickens for culling to fight an outbreak of avian flu in Kiziksa village, in western Turkey, Oct. 11, 2005. (AP Photo/Anatolia/Emre Umurbilir)
What are the different kinds of avian influenza?
There are 15 different strains of bird flu. The mildest – the low pathogenic form – often goes unnoticed, except that hens may produce fewer eggs. More severe kinds spread rapidly and kill many of the birds they infect. The virus that hit poultry in B.C.'s Fraser Valley in February 2004 – the H7N3 virus – is highly pathogenic.
Three subtypes of the influenza A virus – H5N1, H9N2 and H7N7 – have jumped the species barrier between birds and humans.
How does bird flu spread?
Migratory waterfowl – especially wild ducks – carry the virus, but aren't killed by it. They can spread the virus to farm birds through direct contact or through contaminating water supplies.
Domestic poultry, including chickens and turkeys, are particularly susceptible to the kinds of epidemics that spread rapidly – and kill most infected birds.
Epidemics often follow direct or indirect contact of domestic flocks with wild migratory birds. Live bird markets – where a large number of birds are in small spaces – have also played an important role in the spread of epidemics.
In B.C.'s Fraser Valley, officials speculated that dust from wood shavings used as bedding was being fanned out of one infected barn by the exhaust system – and that led to the outbreak.
Officials from the World Health Organization attributed the spread of bird flu to humans to contact with the droppings of infected birds. Investigators in the two Hong Kong outbreaks said they were facilitated by poor sanitation and slaughtering practices in outdoor poultry markets close to housing areas. There was no evidence that either subtype of the virus spread from person to person.
In Vietnam, a 21-year-old man came down with bird flu in February 2005 after drinking raw duck blood.
There is no evidence that people can get avian flu from eating poultry.
How is the spread of outbreaks among birds controlled?
Infected farms are placed under quarantine and infected flocks – or flocks at risk of being infected – are killed. In B.C.'s outbreak, more than 17 million birds were ordered killed, devastating the province's poultry producers for most of 2004.
How many people have been affected?
The WHO said since bird flu first emerged in Hong Kong in 1997 through April 2006, there have been 192 confirmed cases in people and 109 deaths. That's a death rate of more than 55 per cent, which is considered high for a viral illness. The death rate from SARS, for example, was less than 10 per cent.
New flus have appeared consistently over the years. So what makes this flu so scary?
Throughout history, every new flu strain has been scary because it catches the human immune system unprepared. The death toll from a new flu is always higher. But H5N1 is extra scary because it resembles the most infamous flu virus of all time, the 1918 Spanish flu strain, the one that infected half the world's population, killing more than 40 million people.
For years, the Spanish flu virus was a mystery until scientists dug through old U.S. army autopsy samples and collected enough of the virus to genetically reconstruct it. What they found was an avian flu that has a lot in common with today's H5N1.
Michael Osterholm, an infectious disease expert at the University of Minnesota says, "H5N1 is very similar to, if not a kissing cousin to, the H1N1 virus that we saw in 1918. Not only does it act the same way with the kind of immune response it elicits, it is a lethal killer in animals and humans."
Most of the human cases have been in Southeast Asia. But cases have also turned up in Turkey and Iraq.
"We've only been able to identify people who have been sick and who have come to hospital. Maybe there's twice as many or 10 times as many out there that got mild disease," says Dr. Donald Low, a microbiologist at Toronto's Mount Sinai Hospital.
"So maybe the mortality rate isn't 50 per cent. Maybe it's only five per cent; five per cent is still unacceptable. When you think of the potential for pandemic influenza, the number of people that it can infect, that is, 30 to 50 per cent of the world's population."
Another disturbing thing about H5N1 is that the virus provokes such a strong immune response that the body ends up killing itself by causing a collapse of the circulatory system In 1918, the highest number of deaths by far occurred in those 20 to 40 years of age. Even in today's modern, intensive care units, these patients often have a very, very poor outcome.
Right now, H5N1 is not that good at infecting people. It has not yet figured out how to pass easily from person to person.
How do you catch the flu from birds?
In order to get it from birds, H5N1 has to be already in the bird population. The bird sheds the virus in its droppings, and then the human inhales it or ingests it, and every time that happens, the virus gets another chance to practise causing human disease.
Dr. Donald Low says, "A bird that is either sick or not even sick, a bird that's excreting the virus, virus is all over its feathers and its body and people handling it, their hand goes up to their mouth, transmits into their respiratory tract a high dose of the virus, causes disease."
Can we produce a vaccine to protect us from this flu? If we can, why don't we start producing this vaccine now?
Flu vaccines need to be updated every year because the viruses are always changing. As an experiment, U.S. scientists created a test vaccine against an old version of H5N1, and it does seem to work, but only when given in large amounts. If people were given that test vaccine, it might offer some protection against a future pandemic version of H5N1. But the bad news is that, at the moment, there is no way the world could make enough of the vaccine to go around.
Osterholm says, "The real problem is we don't have the production capacity. On a worldwide basis right now, given the amount of egg-based virus that you would need to make the vaccine, we can probably protect in a year's time after the pandemic begins between 85 to 100 million people worldwide. That's it. That's less than 1.5 per cent of the world's population. So until we greatly expand production capacity, which will take years to do, vaccine is only going to have a limited impact on this pandemic."
How do average people protect themselves while maintaining a regular lifestyle?
There isn't much the average person could do in the midst of a pandemic because the virus will spread so fast.
Donald Low says, "There's not a lot that you can do once it happens. There's no question, though, that the old adage about washing your hands, using cough etiquette, staying home if you're sick, staying away from people who are sick, will decrease the likelihood for transmission. This is not an airborne disease, at least not principally an airborne disease, so there are ways that you can protect yourself, but it's not going to work if you think I'll just head for the hills, I'll go to the cottage. We can't all go to the cottage for eight weeks. This is going to be something that is in our community for several months possibly, and we can't stop living.
Things will be a long way from normal in the midst of a pandemic. In a worst-case scenario, two out of every 100 people will die. That also means 98 out of every 100 people will survive, and somehow the economy will have to keep going, and that is something the experts say the world can plan for
Osterholm says: "We're going to have to figure out how do we get food to our people if we shut down the global transportation system? How will we get other drugs, the kind of drugs we need every day in terms of cancer treatment, insulin for our diabetic patients, et cetera? How are we going to handle those who die?"
Supplies are being stockpiled, and the emergency plans are being written. The experts are being paid to worry. So, for the average person, relax if you can.
We hear of the drug Tamiflu as a possible treatment for influenza. It's also reported to have an effect preventing the disease. How long does that preventive action last?
 (File photo: Dimas Ardian / Getty Images)
One pill protects you for one day. Based on the history of other pandemic influenzas, experts believe the first wave in a given area would last up to 100 days. So if you were trying to protect yourself from infection, you would need to stockpile about 100 doses of Tamiflu and start taking them from the moment you hear the virus is circulating in your region.
If you're a government right now trying to stockpile millions of doses of Tamiflu and you want them tomorrow, you're not getting them. Political pressure is mounting to find ways to produce more Tamiflu more quickly.
Why are there more cases in the winter months?
Avian influenza viruses become more active in cooler temperatures. Poultry marketing, transportation and consumption also increases in places like Vietnam with the approach of the Lunar New Year in early February.
Those factors combine to create ideal conditions for the virus to spread.
What happened in the Hong Kong outbreak?
The 1997 outbreak of avian flu, subtype H5N1, killed six people and infected 12 others in a small, densely populated part of Hong Kong. Nine of the cases were in children under 10. Two years later, two cases of avian flu, this time of the subtype H9N2, were found, also in Hong Kong.
Are the avian flu and SARS related?
No. SARS is caused by a coronavirus similar to one of the types of virus that causes the common cold. Avian flu is caused by an influenza virus. However, both viruses originally occurred in animals and spread to humans.
Can mosquitoes spread avian influenza, like they spread West Nile virus?
No. Mosquitoes have never been found to transmit any kind of flu virus.
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| INFORMATION: |
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| PREVENTING THE FLU |
What you can do:
- Get a flu shot. There is no vaccine for avian flu but it may boost your overall immunity, health officials say.
- Wash your hands to wash away the flu virus
- Cover your mouth when you sneeze or cough
- Stay home if you are sick.
- More on what you can do here
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| QUICK FACTS: |
Definition:
The flu is a contagious respiratory illness caused by influenza viruses. It can cause mild to severe illness, and at times can lead to death. Bird flu is an infection caused by avian influenza viruses. (Source: CDC)
Symptoms of flu/avian flu:
Fever, fatigue, cough, sore throat, eye infections, muscle aches.
Transmission:
Infected birds shed flu virus in their saliva, nasal secretions and feces. Avian flu may have passed to humans by contact with infected poultry or contaminated surfaces. In human-to-human cases, flu viruses spread in respiratory droplets caused by coughing and sneezing. (CDC)
Prevention:
Get a seasonal flu shot, wash your hands, cover your mouth when sneezing, stay home if you are sick, consult your doctor.
Avian flu vaccine:
It is under development but cannot be finalized until the pandemic version of the virus appears.
Cure: A healthy body's immune system can often combat the flu. Antiviral drugs may help. Antibacterials are ineffective because the flu is a virus.
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| VACCINE & ANTIVIRALS: |
DEFINITION
Vaccines and antivirals are different. A vaccine is designed to procure immunity from a disease.
An antiviral drug is commonly used to treat an existing illness. Antivirals can also be used in a preventive way, but they are not vaccines, and do not provide immunity.
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