Well as you all know the so-called swine flu is about to hit its second wave in the US and the northern hemisphere in general. However, what you may not know is that I have become a flu expert since coming to Africa. I am taking an immunology class and this portion of the lectures is virology. Our professor thought that since we are in the midst of a pandemic, that we should learn about the flu. So I thought that I would pass along a little of the information that I have learned along the way.
Firstly, I thought that I would explain how flu is categorized. There are three types of Influenza virus (A, B, and C) however; type A is the only type of Influenza that creates a pandemic. In terms of Influenza A, the strains are differentiated from one another by the molecules on the outside, the H (Haemagglutinin) and N (Neurominidase)molecules. Numbers denote the type of H and N molecules. There are seven different H types and 9 different N types that infect pigs, birds and humans. Though, only H1-H3 and N1-N2 infect humans at this point. However, the so called avian flu is H5N1 and has been known to infect humans so on rare occasions H5 is also infectious.
Pandemic flu is not new to the world. Most people know of the 1918 Spanish flu, but even before this instance flu pandemics have been apparent. In fact, the seasonal flu is a slightly modified version of the most recent pandemic flu. This generally means that if you get flu one year, you are probably at least partially immune to the variety that comes the next year. The two most recent strains of flu in our seasonal flu before the 2009 outbreak was a re-release of the 1928 Spanish H1N1 from a lab somewhere and a strain of the “Hong Kong” flu, an H3N2 variety that was pandemic in 1969. Therefore, our vaccines at the moment usually contain last year’s mutation of three strains; one H1N1, one H3N2, and one influenza B variety. These strains co-circulate until the next pandemic outbreak, like one that happened this year.
So how do pandemics come about because it seems that flu mutates slowly year by year not causing a whole lot of a fuss most of the time. Well pandemics arise because flu can cross the species barrier. Interestingly pigs can be infected with both bird and human flu. Also, because pigs are transported all over the world for various reasons, it creates an interesting vessel of study in terms of influenza. From analysis of the 2009 H1N1 so called “swine flu” it seems that this variety shows a distinct ancestry to the Spanish variety but is so genetically diverse that it is considered a completely different strain. The hypothesis is that the 1918 H1N1 parted ways with the 2009 H1N1 in that the 1918 variety infected pigs as well. Since then, the virus has been infecting pigs and mutating within them and picks up genetic material from other strains of flu. The virus stayed in pigs until 2009 when it crossed the species barrier successfully. Crossing the species barrier isn’t the largest issue however. Many times flu and other diseases cross the species barrier. People are familiar with the bird flu and many events where birds have infected humans with flu but most of the time, the virus is not equipped to spread human to human. In 2009, an influenza virus that had been mixing and diversifying in pigs for about 80 years crossed the species barrier and was able to infect humans! This is what created our pandemic flu. In fact it has subsequently displaced all of the other flu varieties and the only infectious influenza A variety is the swine flu.
The reason that the virus killed so many people to begin with, was because it had adapted to pig populations. It is not very advantageous for a virus to kill its host because then it cannot spread therefore, as time went on the disease lost much of its danger in killing people as it adapted to human populations. That being said, it is interesting that the people most susceptible to the new virus are pregnant women and young people. The only theory about the age of the person is that older people have seen more varieties of flu over their lifetime and may be partially immune to this virus, though they don’t really know at all.
Scientists are obviously very curious about this new flu and it course in the near future. Some are concerned that it will mix with the very deadly avian flu and this could be the next outbreak, but who really knows. It seems like a lot of hype to me. My advice is to get yourself vaccinated because I hear that the second wave is always worse than the first and my prof urged the Americans/Europeans to tell our families to get the vaccine so that is what I am doing? I hope that you are all well and don’t get flu this season but if you do, you now know where it came from!
End public service announcement!
The next few pictures were just comics that were a part of the lecture. I thought they were pretty funny so I decided to share them with everyone!
How to protect yourself against avian flu!
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