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INDEPTH: AVIAN FLU
Avian flu and vaccinations
CBC News Online | October 24, 2005

Is there a vaccine for avian flu?
Are health officials worried about any of the particular strains of avian influenza virus?
Why don't they just develop a vaccine for H5N1?
What's the difference between vaccines and antivirals?
What is Canada doing?

Is there a vaccine for avian flu?
No. There are at least 15 strains of avian influenza. And while some of them are very deadly among bird populations, none of them has been linked to human-to-human infection on any scale.Dozens of people have come down with avian influenza since it first appeared in people in Hong Kong in 1997. More than 40 people have died from the disease. But far, far more people contract – and die from – regular strains of the flu.

Vaccine makers concentrate on flu strains that are likely to circulate that year. Flu viruses mutate often – their characteristics change rapidly and permanently. It takes at least four months to develop new vaccines to combat strains of the flu that emerge.

Are health officials worried about any of the particular strains of avian influenza virus?
They're worried about a few of them – especially H5N1.

Health officials say there are three conditions essential to turn a flu virus into a flu pandemic.

It must emerge from an animal and never have infected humans before – that means the population won't have any immunity.
The virus actually has to make humans sick – most of them don't.
It must be highly contagious through handshaking or coughing.

H5N1 has met the first two conditions. Many health experts say the third condition is just a matter of time.

Why don't they just develop a vaccine for H5N1?
Again, because flu viruses change characteristics frequently. It's what makes them such a concern.

For instance, a vaccine developed from the H5N1 virus that is currently spreading in parts of Asia would likely offer little protection from a virus that sparked a pandemic two years later. It would be useless if another of the many subtypes of influenza triggered a pandemic instead, such as the H7N3 strain behind the B.C. avian flu crisis of 2004.

However, a genetically modified seed strain for H5N1 vaccine development is available and vaccine manufacturers in several countries, including Canada, have acquired this seed strain.

Manufacturers are working to optimize the conditions under which the modified H5N1 virus grows in eggs. This will allow them to develop a virus seed bank for future vaccine production.

The virus has been modified using a technique called reverse genetics so that it can grow in chicken eggs, the main source of influenza vaccine production. The genetic modification also makes the virus less virulent.

It's basically an attempt to get a head start, in case H5N1 becomes easily transmittable from person to person.

Still, the World Health Organization says it may not be necessary for Canada to consider stockpiling H5N1 vaccine when it's developed. The WHO says the steps Canada has taken in its Pandemic Influenza Plan leave the country well prepared for the next pandemic.

The WHO estimates Canada's efforts would probably cut four months off the time it would need to produce enough vaccine to cope with a pandemic.

What's the difference between vaccines and antivirals?
Vaccines cause the production of antibodies against the flu virus prior to being infected through exposure to a sick person. When an immunized person is exposed to a person with influenza the antibodies generated in response to the vaccine are ready to attack the virus as it enters the body and prevent illness.

Getting a flu shot is supposed to keep you from getting sick. Antiviral drugs work by reducing the ability of the virus to replicate, once a person is already infected.

More on antivirals

What is Canada doing?
Canada was among the first countries to order Tamiflu, buying 23 million doses to treat those who are already infected and protect essential workers from becoming infected. The risks are that the pills have a guaranteed shelf life of only five years, and there is a risk that widespread use among patients could lead to resistant strains of the flu.

There is such great demand for Tamiflu that the manufacturer, Roche Pharmaceuticals, has licensed several generic drug companies to produce the drug. If there were a shortage during an outbreak, governments could likely override the Roche patent and produce the drug generically in order to meet the demand.

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INFORMATION:

Public Health Agency of Canada for the public:

Tel: 1-800-484-8302
Email
Local Health Canada phone numbers

QUESTIONS:

Send us your questions about bird flu. We'll get the experts to answer them.

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

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.

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.

EXTERNAL LINKS:

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Cumulative Number of Confirmed Human Cases of Avian Influenza A/(H5N1) Reported to WHO

Canadian Food Inspection Agency avian flu

Canadian pandemic influenza plan

Public Health Agency of Canada

Latest information for travellers from the Public Health Agency of Canada

WHO avian influenza

WHO - estimating the impact of the next influenza pandemic

U.S. Centers for Disease Control - Avian flu

UN Food and Agriculture Organization Avian Influenza site

World Organization for Animal Health

EU Avian Flu site

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