The Editor,
The grip of winter and influenza seem to go hand in hand. You may have been hearing reports of larger numbers of influenza cases in Ontario being referred to as a "flunami."
Last year the world experienced the H1N1 pandemic; this year the seasonal influenza viruses have returned. Every year several influenza virus strains circulate the world. Most change slightly over time and some strains become more numerous than others. Six months before winter scientists get together to look at the patterns of influenza strain and determine what three strains should be in the annual seasonal vaccine. Most years it is a good match for all three strains.
The body reacts to influenza by sending its protector cells to the airways and the lungs. This makes the lung lining thick and the lungs and heart have to work harder to breathe. This added strain can cause severe sickness in young and old people, and in those with chronic conditions. That is why these groups of people are encouraged to get the seasonal vaccine.
How many people die each year from seasonal influenza? The Centers for Disease Control in the U.S.A. believe 3,000- 4,000 people a year die directly from influenza in the USA and another 40,000 -50,000 are "tipped over" by the stress to their other condition or die from secondary pneumonia. It is estimated in Canada that there are 4,000 - 8,000 influenza associated deaths every year.
Sometimes a sudden change may occur in the genetic makeup of an influenza virus, so much so that the immune system of a human no longer recognizes it as a virus it should know. This is when a pandemic may occur.
A healthy person may react very differently to a novel virus. In some the immune system goes into hyperdrive against the unknown invader. It overreacts. It sends so many protector cells to the lungs that the lungs become very soggy with inflammation and it becomes impossible to breathe. This happened in the SARS pandemic and the 1918 influenza pandemic.
The 1918 influenza pandemic killed more people in six months than the total of the two world wars. Most were young adults. Stories and records dating back from the Greeks in 412 B.C. tell us that influenza pandemics occur regularly every 30 to 40 years. They spread world wide but differ in the severity of the disease they cause. Most people today will experience another pandemic in their lifetime.
In April 2009, Mexico informed the World Health Organization that its hospitals were full of people with influenza and pneumonia. The virus was identified as a new influenza virus, H1N1, a mixture of bird, human and pig influenza viruses.
The world needed to react quickly on very little information, as it takes several months for a vaccine to be produced.
After some weeks it became clear that for most people the virus was going to cause only mild illness. Most people over the age of 55 years were spared. It is likely that a significant part of H1N1 or a sufficiently similar virus was here over 50 years ago and at the time gave people an immunity that protected them in 2009.
The H1N1virus did affect some healthy young people, many of these spent long weeks in intensive care. The numbers ill and hospitalized indicated young children and pregnant women were more vulnerable than others to severe illness. As in 1918, indigenous people were more likely to get severe disease.
In Saskatchewan the vaccination program began in earnest in the north on October 26. That first week there was five people with influenza-related illness evacuated by air. No further cases of significant illness from H1N1 in the north occurred from that date. By mid-December 50 percent of the Saskatchewan population was vaccinated and the virus had disappeared. There were simply not enough non-immune people to spread it.
The story did change day to day as more was discovered about the virus, who it was affecting, and how severely. Many people spent long hours examining the data and the processes to ensure that the vaccine, produced so quickly, would be safe. The calmness and patience of Saskatchewan residents played a key role in the effectiveness of our entire pandemic response.
There are many, many lessons from the 2009 experience which will help Canada and also the global community to respond to both seasonal and pandemic influenza in the future. And as always, the best ways to prevent the spread of infection continue to be handwashing, coughing into your sleeve, staying home when ill, and getting immunized.
For what you can do this season and for more information on influenza visit the health website at www.health.gov.sk.ca/influenza-flu
Dr. Moira McKinnon,
Provincial Chief Medical Health Officer
