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'Normal' flu season packed with surprises Add to ...

It’s flu season in the Northern Hemisphere and, unlike last year, there is not the drama of H1N1, nor the unprecedented attention influenza was afforded by media and public health officials as a result.

Instead of one global pandemic, there are a series of outbreaks of different types of influenza in various parts of the world and they garner only local press coverage.

The pandemic was declared over in September but this is not to suggest that influenza A/California/H1N1 (the official name for the pandemic strain) has gone away; rather, it has become a seasonal strain and is still doing damage.

Paradoxically, this “normal” flu season will likely prove far more deadly than the pandemic. About 18,000 people worldwide died of H1N1 (including 428 in Canada). But the seasonal flu kills somewhere between 250,000 and 500,000 people each and every year.

But, as Margaret Chan, director-general of the World Health Organization noted in her review of H1N1, influenza is “unpredictable and prone to deliver surprises.”

Here is a brief overview of influenza hot spots around the world:

H1N1 STALKS EUROPE

H1N1 has returned with a vengeance to parts of Europe.

In the past week, the number of cases of influenza has soared by 40 per cent in Britain and Ireland, and 36 deaths have been reported.

While seasonal influenza usually disproportionately affects the frail elderly and the very young, H1N1 is unusual in that it tends to infect young adults. That is the case in Britain, though with a twist – a significant number of pre-schoolers are getting very ill and dying.

It is believed Britain is being particularly hard-hit because H1N1 vaccination rates are low. To quell the outbreak, Health Secretary Andrew Lansley has publicly urged people to be vaccinated. He is also re-launching the “Catch it, bin it, kill it” campaign urging the use of tissues and hand washing to limit the spread of the flu.

The World Health Organization also reports outbreaks of influenza in 13 other European countries, including Sweden, France and Russia, and the majority of cases are H1N1. In Sweden, deaths and serious illness in several young children with the flu have dominated the headlines.

NORTH AMERICA IS H3N2 TERRITORY

In North America, flu season is in full swing, but, unlike Europe, there are very few infections with H1N1.

In Canada , the predominant circulating strain is H3N2 influenza, a seasonal flu that is affecting largely the frail elderly.

While seasonal flu tends to spread from east to west, so far this year it is hitting hardest in southern Ontario and the Prairies.

In the United States, cases of influenza are pretty evenly split between H3N2 – a strain of influenza A – and various types of influenza B. (There is influenza C but it rarely causes illness and is not tracked.) To date, the hardest hit state is New York, along with four southern states: Alabama, Mississippi, Georgia and Virginia.

The flu vaccine is updated each year and this year’s protects against influenza A/California/H1N1, A/Perth/H3N2 and B/Brisbane.

BIRD FLU SPREADS ITS WINGS

Avian influenza H5N1 is a concern on a couple of levels: 1) It can spread readily among fowl, posing a huge problem for the poultry industry and; 2) if the disease mutates and jumps to humans there are fears it could be dangerous, particularly since there is no effective vaccine.

South Korea confirmed this week that it had detected several infected birds and ordered a mass poultry slaughter. The country’s agricultural industry is reeling because, simultaneously, there is an outbreak of foot-and-mouth disease, a highly contagious illness that affects cattle, swine, sheep and goats. (The disease does not spread to humans but there is an identically named human illness that is caused by another member of the picornavirus family.) As a result, South Korea has imposed draconian quarantine measures on a number of poultry, dairy and cattle farms.

In recent weeks, there have also been outbreaks in poultry in Vietnam and Nepal. There have also been human cases of H5N1 reported in Egypt and Indonesia.

In total, the WHO catalogued 44 cases of avian influenza in 2010, 22 of which proved fatal.

FLU AROUND THE WORLD

Influenza tends to spread in a predictable manner, with new strains originating in temperate, populous parts of the world where people tend to live in close proximity to swine and poultry. (Flu viruses mutate in swine – and to a lesser extent in birds – and spread to humans.) While H1N1 was the exception – the pandemic strain first emerged in California and Mexico – flu experts pay particular attention to what happens in Asia as a harbinger of what the rest of the world can expect.

This year’s flu season in China, to date, has been dominated by H3N2 with a smattering of influenza B.

In nearby Korea and Japan, however, H3N2 was the predominant strain but of late there has been an unexpected resurgence of H1N1.

In the Southern Hemisphere, flu season is over and their experience can also be indicative of what to expect in the Northern Hemisphere.

In Australia in 2010, the flu season was unusually mild but in December – when the season is usually over – there was a significant upsurge of H1N1 infections.

There is also a major out-of-season outbreak of H1N1 flu in Sri Lanka currently.

This could serve as a warning to Canada that its flu season may not follow traditional patterns.

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