Seasonal Flu

Annual flu epidemics are nothing to write home about. Everyone knows the feeling – aches and pains, a temperature and a horrible cough and cold. All are the unfolding symptoms of a regular bout of flu.

The illness is caused by an infection of the influenza virus which attacks cells of the air passages and lungs. There are several different types of flu virus that circulate globally in human populations.

The important fact to note about the virus that causes annual epidemics is that it continually undergoes small incremental changes in form. A dose of flu will only confer subsequent immunity to that one specific form of the virus. A few months later the same virus will have altered just enough to confuse the immune system and cause disease a second time around. This is also the reason why new flu vaccines have to be administered annually and, indeed, it explains why they sometimes don't work.

Common though it is, flu is actually no joke – every flu season has its fatalities. Exact figures are difficult to come by but the World Health Organisation estimates that 5-15% of the global population fall victim to flu-type infections annually. These regular epidemics are each thought to result in 3-5 million cases of severe illness and between 250,000 and 500,000 deaths. Most deaths associated with flu occur among those over 65 years of age.

Flu is one of the least feared but most deadly diseases on the planet. Although it doesn't kill a high percentage of its victims, it works by infecting very large numbers of them, and by these means it kills large numbers.

Having said that, the vast majority of us can get over flu with a little old-fashioned TLC. So why all the doom-mongering over a deadly global pandemic? How bad can it get?

Bird to Human Flu »»

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