H1N1 Swine Flu – Basic Information

Swine Flu – Basic Information

EDU – Swine Flu – Basic Information
Credit to JJackson of Flu Trackers Team

I can see we have a lot of ‘lurkers’ – I hate that term as I think it has pejorative overtones when all it means is readers who have not signed up to comment. Many, I suspect, are relatively new to all things Pandemic flu related and will be confused by the ‘swine flu’ stories appearing in the main stream media (MSM) when up until now ‘bird flu’ has got all the ink. What follows is some background which I hope will help you in understanding this unfolding story.

All flu’s originally come from birds. There are three Types A, B & C and we are only interested in Type A here. They are simple viruses with eight strands of genetic material (RNA) which include instructions for making eleven proteins. Two of these proteins Hemagglutinin (H) & Neuraminidase (N) are used to classify flu’s. There are 16 Hs & 9 Ns giving 144 possible combinations from H1N1 to H16N9 these are called SeroTypes (also known as SubTypes). Flu mutates very rapidly and each of the RNA strands is constantly varying about a theme and these are called Strains. As mentioned, birds are the natural carriers of flu but occasionally one of these strains drifts to a point where it happens to also be capable of infecting a mammal. Normally when this happens it is due to close contact and the story goes no further and the animal is a ‘dead end host’ in that it does not spread the infection to others. On extremely rare occasions the animal does spread to other animals of the same type and if this can be sustained the virus may adapt to its new host species and stop being a bird disease and become a swine or horse or human flu. All three of these animals are now the natural hosts for their own flus. In each case the flu would have originated in birds but, now that it is fully adapted to its new host, would have difficulty transferring back to birds.

Humans have only two Serotypes of Type A seasonal flu which circulate each winter; H1N1 and H3N2. Occasionally others, like H5N1(avian), cause the odd infection in humans but transmission is not sustained. There are also infections from pigs, but again generally in people who work with pigs, and not sustained. H5N1(avian) has caused a steady trickle of human cases since 2003 and as some of these have managed to infect other people the fear was it might make further changes until it could be self-sustaining in humans starting a new pandemic. While we were aware that any non human flu could start a pandemic this was a particularly lethal strain which had shown some human adaption so got a lot of attention.

So much for the background what is happening now?
A new pandemic candidate has emerged this time it is H1N1(swine). H1N1(human) is one of the seasonal flu strains but this is a human adapted flu. There are also H1N1 strains in birds and pigs and they are each adapted to their own host species and normally stay there. Unfortunately a new strain has jumped from pigs into humans and is spreading from human to human. I will use H1N1(sw-hu) as a shorthand for this one as it is now reproducing and spreading in humans but is still genetically very swine like in character. If it gets any better at living in us it may become unstoppable and go pandemic.

What about vaccines and antivirals?

Our immune system has many parts but they can be broadly split into two categories Innate & Adaptive. The Innate system needs no prior knowledge of a pathogen, if it does not recognise it as ‘self’, it attacks – however it is generalised and less effective. The Adaptive part of the system is made up of specialised tools for attacking threats it has met before. If an unrecognised virus appears the Innate system will try and deal with it but you may become quite ill while it builds a targeted Adaptive response. If you have had the disease before then both parts come into play and you are said to have immunity – or partial immunity. In the case of flu it is fighting an evolutionary battle with our immune system and is continuously varying its surface proteins (H & N) to avoid recognition. When we vaccinate someone we are deliberately using something to make the body think it is being attacked by a particular strain so when it meets it again it has a primed Adaptive immunity. After a year flu can change so much that last years infection, or vaccination, may not be enough to protect you. Any swine or avian H1N1 are likely to be such distant cousins that even if you have just had a shot for seasonal H1N1 it probably will not help much, if at all. Unfortunately it takes several months to make reasonable amounts of flu vaccine and you need a sample of the right strain to start. If the WHO decides this H1N1(sw-hu) is going pandemic it would ask all the seasonal flu manufactures to stop production of seasonal flu vaccine and switch to H1N1(sw-hu) vaccine production.

The CDC, in the US, say that H1N1(sw-hu) is susceptible to both Tamiflu and Relenza, the main antiviral drugs, but not to the older ion blockers. Seasonal human H1N1 is largely resistant to the common Tamiflu (tablet), but still suseptible to the less common Relenza (inhaled powder). A further note is that flu has a habit of swapping genetic material with other flus if you get dual infections and this happens more easily if they are similar strains. While H1N1(seasonal) may be far enough away from H1N1(sw-hu) for the vaccine not to work it is close enough for there to be a real danger of it learning Tamiflu resistance in short order.

Achak Snowy Owl


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