Medical Fun Facts Episode 70: What is a pandemic

It’s Monday 12 June 2017.

It’s a public holiday in Canberra

We’re celebrating the official but not the real birthday of Her Majesty Queen Elizabeth II

Check out the YouTube video to see my reaction to Her Majesty's birthday.

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Show notes are available at http://DrGaryLum.com/Blog

After episode 69, I got a bit of a bump in views on the blog, listens to the podcast and views to the YouTube video.

I was going to take a break but I thought I should do a short podcast especially since I’ve got a long weekend to get this done.

Today’s show is a result of a question I got on Twitter.

If you have any questions, thoughts or ideas please let me know.

You can Tweet me, write a comment on the Facebook page, write a comment to this blog post below, write a comment on YouTube or send me an e-mail via my contact page.

The question I got via Twitter was about pandemics and specifically about pandemic influenza and what is antigenic drift and shift.

So, what is a pandemic? Watch the YouTube video for the details

Different types of pandemic

Influenza pandemics in modern history

1918 Spanish influenza H1N1

1957 Asian Influenza H2N2

1968 Hong Kong Influenza H3N2

2009 H1N1 pandemic

What’s the difference between seasonal influenza and pandemic influenza?

Each season small genetic changes occur in the main circulating influenza viruses

When this happens, there is sufficient antigenic difference that our immunological memory won’t provide full protection but only some cross protection.

The changes in the antigens are usually only small, they drift a bit, hence antigenic drift.

The changes accumulate so then the difference is big enough a person who has been infected previously may get infected again and develop influenza the disease

It’s why the immunisation preparation changes each year to reflect the subtle changes.

Antigenic shift reflects a significant change in an Influenzavirus A virion. This could mean a whole new hæmagglutinin and/or new hæmagglutinin and neurominidase proteins.

The hæmagglutinin is the H in the virus designation and the neurominidase is the N component.

When there are changes in these components, the resulting virus is so different that immunity in humans probably doesn’t exist. Even though the pandemics in 1918 and 2009 were both H1N1 viruses, they are very different viruses antigenically.

Antigenic drift and shift occurs in Influenzavirus A virions and antigenic drift only in Influenzavirus B.

I hear you ask what is important about the B virus and why does the seasonal immunisation contain antigens from 2 × Influenza B viruses? The Influenzavirus B cause more severe infection and disease in children, that’s why it’s included.

One more thing, you often hear people talk about how they are sick with the ‘flu. More often than not, upper respiratory tract infections which give rise to a headache, sore throat and nasal congestion are caused by other viruses like rhinoviruses, coronaviruses, enteroviruses and a few others. This common cold illness is very different to true influenza which is usually very incapacitating with fever, cough, muscle and joint pain along with severe headache, malaise and lethargy.

After influenza, depression can occur and secondary bacterial infection with the golden staph can also occur. In some people the secondary bacterial infection can lead to a cavitating pneumonia which can be deadly.

Apart from pandemic strains, every year, people at the extremes of age, the frail and infirm, succumb to influenza. It’s a good reason for people in those categories to be immunised.

If you’re in a risk group for influenza, you should consider annual immunisation. Likewise, people who live close to you should consider it too.

It’s remarkable to think there are people out there who believe that immunisation is harmful and a ploy by governments and pharmaceutical companies to financially rip off and physically harm humans. The benefits of immunisation are plain to see for anyone who is prepared to weigh the abundant evidence before us.

At the 9 minute 26 second mark I meant YouTube not iTunes

And so, ends another episode of Medical Fun Facts. If you have suggestions or requests for future shows please let me know. You can find the show notes for every episode at my blog http://DrGaryLum.com/Blog

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