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Influenza (the "flu")

It's Your Health

This article was produced in collaboration with the Public Health Agency of Canada.

Help on accessing alternative formats, such as Portable Document Format (PDF), Microsoft Word and PowerPoint (PPT) files, can be obtained in the alternate format help section.

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The Issue

Influenza (or flu) is a common respiratory illness that affects millions of Canadians every year. Getting an annual influenza vaccination (or flu shot) can help prevent an infection or reduce the severity of the illness.

Background

Influenza is a respiratory infection caused by the influenza virus. Various strains of the virus circulate throughout the world -- causing local outbreaks -- year-round. In Canada, flu season usually runs from November to April, and an estimated 10-25% of Canadians could have the flu each year. Although most of these people recover completely, an estimated 4 000 to 8 000 Canadians -- mostly seniors -- die every year from pneumonia related to flu. Many others may die from other serious complications of flu.

The influenza virus spreads through droplets from someone with the flu, who coughs or sneezes into the air. You can become infected by breathing in these droplets through your nose or mouth, or through the droplets landing directly on your eyes. The flu virus is also found on the hands of people with the flu and on surfaces they have touched. You can become infected if you shake hands with infected persons or touch contaminated surfaces, which can transfer the virus to your own eyes, nose or mouth.

Flu vaccines have been around since the 1940s. The vaccine is made from fragments of inactivated influenza viruses, grown in fertilized hens' eggs and then purified. The flu viruses are capable of changing from year to year, so the composition of the vaccine has to be updated annually. This is why it is necessary to be immunized every fall. About 10 million doses of influenza vaccine are distributed annually during the flu season, in Canada.

After you get a flu shot, your immune system produces antibodies against the strains of virus in the vaccine. When you are exposed to the influenza virus, these antibodies will help to prevent infection or to reduce the severity of the illness.

The Health Effects of Influenza

There is no such thing as the "stomach flu." Many people use the terms "flu" or "stomach flu" to describe other illnesses that may actually be a common cold or a mild case of food poisoning.

These are the symptoms of influenza:

Almost always:

Cough and fever

Common:

Fatigue
Muscle aches
Sore Throat
Headache
Decreased appetite
Runny nose

Sometimes:

Nausea
Vomiting
Diarrhea

Most people recover within a week or ten days. However, some are at greater risk for more severe and longer-lasting complications, such as pneumonia. The groups at higher risk include very young children, people over 65, pregnant women, people with underlying medical conditions such as chronic respiratory disease, heart or kidney disease, diabetes or a weakened immune system due to cancer, HIV infection, or some other cause.

Another possible health effect related to the flu is Reye's syndrome, which can develop in children and teenagers who are given salicylates (aspirin) when they have the flu or chickenpox. Reye's syndrome affects the central nervous system and the liver, and can be fatal. Do not give aspirin to children or teenagers with the flu, unless you are specifically directed to do so by a doctor.

Pandemic Influenza - H1N1 flu virus

The H1N1 flu virus is a strain of the influenza virus that contains a mixture of human, swine, and avian influenza. It is a new strain of influenza against which humans have no immunity.

In June 2009, the World Health Organization classified the H1N1 flu virus as a Phase Six pandemic, meaning this new influenza virus was spreading rapidly among humans.

People are exposed to different strains of influenza many times during their lives. Although the virus changes, people who have had previous bouts of influenza may have some protection against similar strains of the virus. However, for unknown reasons, three to four times each century, a radical change takes place in the influenza, and a new strain of the virus emerges.

Since people have no immunity against a new strain, it can spread rapidly around the world, causing a pandemic -- a global outbreak that affects a large proportion of the population. This is what happened with the pandemic H1N1 flu virus (human swine flu).

The human health effects caused by pandemic influenza can be mild, moderate or severe. The WHO considers the overall severity of the current H1N1 flu pandemic to be moderate, because:

The majority of patients experience mild symptoms and make a rapid and full recovery without the need for hospitalization or medical care.
Overall, national levels of severe or fatal cases of respiratory illness appear to be similar to levels seen during seasonal influenza periods, although in some regions and institutions, high levels of disease have occurred.

The severity of health effects caused by pandemic influenza can change over time if the virus mutates. There is no need to panic, but it is a good idea for Canadian families to take steps now that will help them respond to the H1N1 flu pandemic, as events unfold. Knowledge is your best defense. See the Need More Info? section at the end of the article for links to information that will help you prepare for this pandemic and other emergency situations.

Minimizing Your Risk

Immunization

Immunization is one of the most effective ways to protect against influenza. When you are immunized, you have received a vaccine (sometimes called a shot) containing a dead or weakened virus to help your body learn how to fight off the virus if you are exposed to it.

Vaccines are virus-specific, so to protect against both seasonal flu and the pandemic H1N1 flu virus, you will need two separate flu shots.

Seasonal Influenza Vaccine (Flu Shots)
The most effective way to protect yourself from flu is to be vaccinated each year in the fall. Every year, the vaccine is formulated to protect against the most commonly circulating flu viruses. Seasonal flu shots are especially important for:

children aged 6 to 23 months;
adults and children with chronic heart and lung disease;
anyone living in a nursing home or chronic care facility;
people aged 65 years and older;
people with chronic conditions such as diabetes, anemia, cancer, immune suppression, HIV, or kidney disease;
children and adolescents on long term acetylsalicylic acid (ASA) therapy;
healthy pregnant women;
health care workers, other caregivers, and household contacts capable of transmitting influenza to the above at-risk groups;
people at high risk of influenza complications who are traveling to areas where the flu virus is likely to be circulating.

Certain groups should not be vaccinated. These include children under six months of age and people who have had a severe allergic reaction to eggs or a previous dose of the vaccine. The timing of the seasonal flu vaccine campaigns for the 2009/10 flu season will vary across the country. Please check with the health authority in your region for further information.

Pandemic Influenza (H1N1 flu virus) vaccine

A new vaccine for the pandemic H1N1 flu virus is currently under development. The Government of Canada has announced that it will purchase 50.4 million doses of vaccine along with the provinces and territories. It should be available in November to all Canadians who need and want it.

Those who need the vaccine most will receive it first

All levels of government and scientific experts have worked together to develop a vaccine sequencing list to ensure that those who will benefit most from immunization will received the vaccine first.

Those who will benefit most from immunization include:

People under 65 with chronic conditions
Pregnant women
Children aged 6 months to 5 years of age
Persons residing in remote and isolated settings or communities
Health care workers involved in pandemic response or the delivery of essential health care services
Household contacts and care providers of persons at high risk who cannot be immunized or may not respond to vaccines
Populations otherwise identified as high risk

Others who would benefit from immunization include:

Children 5 to 18 (inclusive) years of age
First responders (healthcare workers)
Poultry and swine workers
Adults aged 19 to 64 (inclusive)

Provinces and territories are expected to use this guidance for planning purposes and will interpret it based on local circumstances and realities.

Vaccine Safety

The benefits of flu shots far outweigh their risks. The flu vaccine cannot cause influenza because it does not contain any live virus. The most common side effect is soreness at the site of injection, which may last a couple of days. You might also notice fever, fatigue and muscle aches within six to 12 hours after your shot, and these effects may last a day or two. Some people develop a condition called “oculo-respiratory syndrome” after a flu shot. The symptoms include red eyes and respiratory effects such as cough, wheezing, chest tightness, difficulty breathing, or sore throat. In most cases, the symptoms are mild and disappear within 48 hours.

Severe allergic reactions to flu shots are rare. A rare but possible side effect of influenza vaccination is Guillain-Barré syndrome (GBS). This is an autoimmune disease that attacks the nervous system and results in weakness and abnormal sensations. Most patients recover fully. Your chance of developing GBS as a result of a flu shot is one in a million.

The primary reason to get a flu shot is to protect yourself from health effects related to flu. However, by getting a flu shot, you will also help protect other Canadians and reduce the burden on the health care system.

Infection Control

To prevent the spread of any influenza virus, and other infectious disease, the Public Health Agency of Canada recommends:

Wash hands thoroughly with soap and warm water, or use hand sanitizer
Cough and sneeze into your arm or sleeve
Keep common areas and shared items clean and disinfected
Keep doing what you normally do, but stay home if you are sick
Check www.fightflu.ca for more information
Talk to a health professional if you experience severe flu-like symptoms

Treatment

If you get the flu, you should increase the amount of fluids you drink (water, juice, soups) and get plenty of rest for seven to ten days. There are also medications to treat influenza. If you take them within 48 hours of the start of your symptoms, they may reduce the length of your illness by an average of one or two days.

Canada has a national stockpile of these drugs, called antivirals, for the treatment of moderate to severe pandemic influenza. This stockpile contains 55 million doses of two different kinds of drugs, Tamilfu and Relenza, which is enough to treat everyone who needs it during a pandemic. Antivirals are not recommended for the treatment of mild illness.

Concerns about Avian Flu

In addition to concerns about the pandemic H1N1 flu virus, there remains a risk that an avian flu (such as the H5N1 Asian strain) could possibly develop into an influenza pandemic at some point in the future. Since 2003, this strain of avian flu has been circulating in Southeast Asia and parts of Europe and Africa. It is deadly to poultry and has infected many poultry populations. A limited number of people have been infected, mainly through close contact with infected poultry.

At the moment, there is no evidence that the H5N1 avian flu virus can spread easily from human to human. However, there are concerns that this virus could mutate or, if someone infected with human influenza also becomes infected with H5N1 avian influenza, the viruses could mix, creating a new strain. If a new strain had the ability to spread easily from person to person, the virus could spread rapidly around the world, causing an influenza pandemic.

Again, there is no need to panic, but it is a good idea to be prepared.

Government of Canada's Role

The Public Health Agency of Canada and Health Canada co-ordinate national activities for the prevention and control of flu. As part of this work, the Public Health Agency of Canada conducts surveillance, along with the provincial and territorial health ministries and other partners, to assess influenza activity and its spread across Canada in real time. Health Canada and the Public Health Agency of Canada also regulate the safety of vaccines in Canada and help co-ordinate the procurement of flu vaccines for the provinces and territories. These activities ensure that supplies of safe and effective vaccines are available when Canadians need them.

In addition, the Government of Canada has worked in partnership with provincial and territorial governments, as well as health care professionals and other key stakeholders, to develop the Canadian Pandemic Influenza Plan for the Health Sector. The Plan is constantly being reviewed and updated to ensure that it is current with the latest developments and science. It covers key areas of pandemic planning and response, including monitoring, vaccine and antiviral programs, emergency services, and risk communications.

The federal, provincial and territorial governments have also worked together to set up a Web portal called FightFlu.ca, which provides a single source of credible information to help you and your family stay healthy and prevent the spread of flu.

A global leader in pandemic planning, Canada is now implementing the overall pandemic plan for the health sector (Canadian Pandemic Influenza Plan). Canada's advanced level of readiness is due to close cooperation with provinces and territories and health professionals across the country.

The Government of Canada continues to address H1N1 flu virus as per the Canadian Pandemic Influenza Plan for the Health Sector, including:

Ensuring that the National Antiviral Stockpile can be mobilized quickly so Canadians can receive the treatment they need;
Reviewing the science and working with the vaccine manufacturer, GlaxoSmith Kline, for the development, testing, and production of the pandemic vaccine;
Managing the National Emergency Stockpile System (NESS) which contains hospital supplies, equipment, and other pharmaceuticals (including antiviral medication);
Assessing the implementation of community-based strategies aimed at mitigating the potential impact on the healthcare system and society as whole;
Working with national professional organizations and non-government organizations to optimize and monitor essential health-related resources and address emerging issues.

Need More Info?

For more information, contact your local public health department or your health care provider.

Also, visit the Fight Flu Web portal
The portal provides you with access to information on flu, as well as links to resources from the provinces and territories. You can also call the Public Health Agency of Canada's Information Line at 1-800-454-8302 (toll-free in Canada) for information about seasonal flu, the H1N1 influenza pandemic, and Avian flu.

Additional Flu Information Web sites:

Health Canada - Influenza

Public Health Agency of Canada - Influenza

H1N1 Flu Virus

For information specific to First Nations, Inuit and Métis - H1N1 Flu Virus

Check out the following It's Your Health articles:

For information on pandemic influenza, see the Public Health Agency of Canada's H1N1 Preparedness Guide

Also visit the Public Health Agency of Canada's Web section for Information for Individuals & Families The resources here, include a Pandemic Flu Planning Checklist and a Flu Prevention Checklist.

Canadian Pandemic Plan for the Health Sector

For more information on Vaccines visit:

The Public Health Agency of Canada's, Immunization & Vaccines Web section

The National Advisory Committee on Immunization (NACI)

The Canadian Coalition for Immunization Awareness and Promotion

Avian Flu Information Web sections at:

Health Canada - Avian Flu

Public Health Agency of Canada - Avian Flu

For information on flu and animal health, see the Canadian Food Inspection Agency's:

H1N1 Flu Virus - Advice for Veterinarians and Swine Producers

Avian Flu

For brochures and fact sheets about preparing for an emergency, see Making a Family Emergency Plan

Also see:

The World Health Organization - Influenza

For additional articles on health and safety issues go to the It's Your Health Web section.
You can also call toll free at 1-866-225-0709 or TTY at 1-800-267-1245*.

Updated: October 2009
Original: November 2002
© Her Majesty the Queen in Right of Canada,represented by the Minister of Health, 2009