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Seasonal Influenza

January 3, 2014 UPDATE: 2013-2014 Seasonal influenza

Since November 2013, the Public Health Agency of Canada has received a number of reports of illness caused by the influenza AH1N1 flu virus among young and middle-aged adults. The H1N1 flu virus strain was first identified in 2009, caused the H1N1 influenza pandemic and is still circulating in Canada and other countries including the United States.

The H1N1 flu virus strain is known to cause more illness in younger individuals, compared to older adults. Most of the flu illness seen so far this season is due to H1N1 flu virus. Although the number of flu cases being reported is not unusual, more severe illness resulting in hospitalization is being observed in those with H1N1 flu virus. Public health authorities are continuing to monitor the situation.

It is not too late to receive a flu shot. All Canadians are encouraged to get vaccinated against the flu to protect themselves and their families as vaccination is the best protection available against flu. The 2013/14 seasonal flu vaccine provides protection against a number of flu viruses, including the H1N1 flu virus strain. Even if you received the H1N1 flu shot or had H1N1 influenza during the pandemic in 2009,you cannot assume you are still protected. You still need to get this season’s flu shot to protect against this season’s flu.

More information related to seasonal flu, including flu clinics near you, and other methods of prevention, can be found at Information for Health Professionals and the Seasonal Flu Public Health Reminder are also available.

Influenza or the flu is a common, infectious respiratory disease that begins in your nose and throat. It is highly contagious and can spread rapidly from person to person. It is estimated that in a given year an average of 12,200 hospitalizations related to influenza may occurFootnote 1; and that approximately 3,500 deaths attributable to influenza occur annuallyFootnote 2.

Fighting the flu is a public health priority and something that all Canadians can contribute to.

Canada’s National Advisory Committee on Immunization (NACI) encourages all Canadians over age six months to get a flu shot. It is particularly important for health professionals to get immunized to protect themselves and their patients. Visit FightFlu.caExternal site – Your one-stop access to information about the flu.

Figth Flu

H1N1 Flu Virus

In Spring 2009, a new strain of the influenza virus, the H1N1 virus, was identified as causing influenza infections in people in North America. As the H1N1 Flu Virus spread around the world, the World Health Organization (WHO)External link declared it a pandemic influenza virus. As it was a new strain of influenza and because humans had little to no natural immunity to this virus, it caused serious and widespread illness.

On August 10, the World Health Organization (WHO) declared that the H1N1 pandemic had entered the post-pandemic period. This decision was informed by epidemiological evidence from around the world showing the H1N1 influenza virus was circulating at lower levels and behaving like a seasonal influenza virus.

Since the end of the 2009 H1N1 pandemic, the H1N1 influenza virus continues to circulate in Canada and other countries including the United States.

Avian Influenza ("bird flu")

Avian Influenza

Birds and other animals, including pigs, also contract and transmit influenza. Wild birds, in particular, are natural carriers of influenza A viruses. They have carried animal influenza viruses, with no apparent harm, for centuries. Migratory waterfowl (ducks, geese) are known to carry viruses of the H5 and H7 strains or subtypes. These viruses are usually in the low pathogenic form - in other words, they aren't as deadly to birds as highly pathogenic strains.

The avian influenza H5N1 virus continues to cause sporadic human infections in a number of countries. There have been some instances of limited human-to-human transmissions among very close contacts. As reported by the World Health Organization (WHO), there has been no sustained human-to-human or community-level transmission identified thus far. The cumulative number of confirmed human cases of Avian Influenza A(H5N1) reported to WHO since 2003, as well as; confirmed Avian Influenza animal outbreaks, can be found at the Current Avian influenza (H5N1) affected areas.

Pandemic Influenza

Pandemic Preparedness

People are exposed to different strains of the influenza virus many times during their lives. Even though the virus changes, their previous bouts of influenza may offer some protection against infection caused by a similar strain of the virus. However, three to four times each century, for unknown reasons, a radical change takes place in the influenza A virus causing a new strain to emerge.

Influenza Surveillance

Flu Watch webpage

To see where the flu is active in Canada, visit the FluWatch web site. FluWatch produces weekly influenza surveillance reports from October to May and bi-weekly reports from June to September each year.

Emerging Respiratory Pathogens

Information on Emerging Respiratory Pathogens for both the public and public health professionals can be found on the Emerging Respiratory Pathogens page.

National Advisory Committee on Immunization (NACI) Statements

The National Advisory Committee on Immunization (NACI) provides the Public Health Agency of Canada with ongoing and timely medical, scientific, and public health advice relating to immunization. Past and present annual statements on Influenza vaccination can be accessed on the NACI web site.

Footnote 1
Schanzer DL, McGeer A, Morris K. Statistical estimates of respiratory admissions attributable to seasonal and pandemic influenza for Canada. Influenza Other Respir Viruses. 2013;7(5):799-808.
Footnote 2
Schanzer D, Sevenhuysen C, Winchester B, et al. Estimating Influenza Deaths in Canada, 1992-2009; PLoS ONE; 2013 (in press).