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H1N1 swine flu explained (FAQs)
- Jun 23, 2009 at 10:26 PM
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I can't imagine there is anyone reading this who has not heard of the swine flu, or heard the H1N1 term thrown around in the news. But I also imagine alot of people reading this don't fully understand what H1N1 means or why swine flu is killing people, yet pork is ok to eat.
My community had it's first H1N1 flu death this past week. We have had some cases around here for a few weeks or longer now, and I have not concerned myself with it too much, although my daughter does attend school outside our home and I work around alot of different people who often travel around the world. So my mom radar is starting to ramp up a little tiny bit, and while nursing Sarah late last night, I read through alot of different influenze-related information.
As you know, my target audience for these posts is the general Cafemom community, non scientist mommies wjo love science, or are just interested in learning a little something new. I am aware some of the posts are a little too detailed and complex, but that is my way of mixing it up a bit and challenging you (and myself) a little bit, too.
Well today it is much more important for you to understand the information than for me to take liberty in writing it out fluently and in my own style. So today you will see my first Q & A post, because understanding the H1N1 flu basics is important if you are going to have a chance at understanding the frequent H1N1 "news".
FLU BASICS
What is influenza? influenza (flu) is a respiratory disease that is contagious, meaning it is easily transmitted among human individuals. It is caused by a virus (therefore antibiotics will not help you fight the flu - they only wrk against certain bacteria). Read more details on the CDC website.
How are different flu types classified? The term TYPE is used as a broad classification of different flus. Type C is a very mild flu that does not become epidemic or pandemic. Type B is usually a mediocre flu that can cause an epidemic (but not pandemic); it does occasionally kill some humans. Type A flu is the most serious, killing many thousands of people during flu seasons each year - this is often called seasonal flu. This flu type is the kind that is serious enough to spread and potentially cause an epidemic and pandemic.
Only the TYPE A flus are further classified into subtype (or strain). SUBTYPES are given a 4 digit designation, for example H1N1 or H3N2, etc.
You may occasionally see the complete flu virus name, for example: A/Hong Kong/156/97 (H1N1) This means: flu type A, originally found in Hong Kong by a lab designated #156 in 1997, known to be of H1N1 subtype.
SOME TERMINOLOGY REGARDING SEVERITY
What is an epidemic? An epidemic is a term used when new cases of a specific disease occuring in a specific population is exceeding what is normally expected. So normal seasonal flu is not an epidemic because it is an expected increase in the disease during the winter months. But when a new strain of flu pops up and causes more cases of the flu than usual - this is an epidemic.
When was the last epidemic? In 2007, a bird (avian) flu in Asia of subtype H5N1 infected many people but I don't believe there were any deaths. China slaughtered millions of birds in an attempt to keep the disease from spreading, though.
What is a pandemic? A pandemic is the term used when a specific disease is spreading through human populations very far from one another. H1N1 flu was just upgraded to a pandemic because it has been detected in many human populations across a wide distance (globally). It does not mean it is killing alot of people - it just means it is SPREADING.
When was the last pandemic? In 1968, 700,000 people died globally from an H3N2 flu subtype. Prior to that, in 1957, 100,000 people died from a H2N2 flu subtype. Prior to that the Spanish Flu of 1918 killed over 40 million people worldwide - this was an H1N1 flu subtype. All three of these flus are also thought to be bird flus that mutated and gained the abillity to transmit between humans.
THE BIOLOGY BEHIND THE FLU
What does it mean for a human to get a bird flu? Many different species have their own seasonale flu viruses, including birds. Just as the human flu viruses change a bit each season, the bird flus do too. Usually only birds get bird flu, but occasionally humans that work with birds can get it, but they can't give it to other humans, so it doesn't really spread around. BUT sometimes that flu virus mutates enough to make it transmissible from human to human, and then it can really spread fast!
How do flu viruses mutate and what effect does it have? Mutations have two main effects: First the mutation can give the virus the ability to be transmitted easily among humans. Second, the mutation can change the proteins on the outside of the virus enough so that our immune systems do not recognize it as something seen before (and thus responding quickly to kill the invaders). HOW these mutations occur is a bit mre complicated, but there are two basic ways: antigenic drift and antigenic shift. I'll explain what they are, but first you need to know a little about the structure of a virus, and how your immune system works.
What is important about the structure of a virus? A virus is a tiny little organism with an incredibly small number of genes (8!!). The flu virus is basically a sphere with its genes on the inside and some proteins coating the outside. It's these proteins on the outside (the viron's coat) that our immune picks up on. In particular, there are two important proteins the virus sticks on it's coat - hemagglutinin and neuraminidase (H and N proteins). These are the two proteins referenced in the H1N1 flu subtype designation. There are 3 types of the H protein (H1, H2, and H3) and 2 types of the N protein (N1 and N2) that are usually found on the virus that infect humans.
The picture above is from 3dscience. See how the virus is a sphere; all thse little balls sticking out of it are the H and N proteins.
What is important about the function of the immune system? Your immune system makes antibodies against all foreign invaders it has ever fought in the past, so in case they come back again, you can fight them very easy the next time. these antibodies basically work by recognizing the foreign invader (such as the flu virus), and activating other cells to kill the invaders. BUT when a new flu subtype comes around, your existing antibodies don't have the ability to recognize it and so no killer cells get activated and you get sick. your body then fights off the sickness AND generates new antibodies so that it will be able to fight off this invader next time.
THE GENETICS BEHIND THE CHANGES
What is antigenic drift? Viruses are constantly making more of themselves and spreading around. As they do this, occasionally some very minor changes in their genes occur. We call these point mutations (simple random mutations), and they really are minor changes to one or both proteins. These mutations do NOT change which H or N protein type (number) is on the outside of the virus. But the change is enough to make your immune system think you have never seen this flu before, and so you get sick. This is the reason why a new flu vaccine is needed each season - the flu virus is always changing the H and N proteins a tiny little bit.
What is antigenic shift? Once in a while a couple different virus subtypes will infect the same host, and while they are there, they mix their genes up and make a whole new virus subtype. For example, an H1N2 virus and H3N1 virus can mix with each other and reassort their genes, making a NEW H1N1 virus. This is essentially where the NEW STRAIN (subtype) of H1N1 flu came from.
So then why is it called a swine flu? It's thought that pigs were the host that got infected by two different virus subtypes, allowing them to fix and form the H1N1 subtype. It just so happens the resulting H1N1 flu is easily transmitting among humans, which is why it has reached pandemic status.
Is this H1N1 the same as the H1N1 that caused the Spanish Flu pandemic in 1918? Not exactly. There are differences in the other genes, and they appear to have come from different species.
I hope this post has been informative but not too confusing for you. I also hope it gets read widely on Cafemom and people ask questions as needed. If anyone is interested in understanding what you should do if you think you have the H1N1 flu, I suggest reading more on the CDC website, or talking to your family doctor. I am not trying to make anyone get frozen in fear - remember KNOWLEGDE is POWER!!
Tonya
AKA sunmoonstars
Comments:
You said swine flu! *runs away screaming*
Uh, sorry. Very informative post, as always. :)
Lol aurorabunny.... I couldn't resist... swine is a funny word :D
As someone struggling with a (the???- dr said didn't matter- flu was flu) flu and a secondary infection- thank you!! I am pretty science minded myself and so was pleasantly surprised to learn something!! I didn't know about the H and N proteins and how all of that works- but it makes sense...
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Interesting. Thanks
- Momforhealth
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