Just as a brief primer for those of you actually interested in Professional Aviation and what a pandemic - any pandemic - means
Please start here: None of what is written below is conjecture. I am simply relaying the information provided by the worlds foremost experts on Influenza A, virology, epidemiology and what a pandemic may mean for us all. Lets start with a set of interviews conducted late in 2005 with many of the world leaders in the relevant fields, so if you are in any doubt about the chances of a Pandemic occurring you might consider reading
this 11JAN06 set of interviews by the worlds experts
So what is a pandemic? It is a world wide epidemic. That's all. It is a widespread pathogen. It does not imply any particular level of morbidity or mortality. But to to become a pandemic strain a pathogen we should be concerned about (in this case Influenza A) must meet three criteria:
1. It must be an emergent virus - that is it has not been seen before. Each virus has a host species in which it is endemic but which usually remains asymptomatic. Typically birds (H5N1), Pigs (H1N1) etc. The host species just acts as a reservoir. Occasional a virus will change such that it can jump the species barrier. A virus can change (some same say mutate) in one of two ways. Antigenic drift - this is a result of the sloppy way copies of the virus are reproduced in the host cell, primarily because a virus is so simple it is like building a house with only roughed out plans.. the end result is often different to the original. Reassortment is when two different virus infect the same cell there may be some swapping of genetic info between the virus' so that a new one emerges containing properties of both precursors. The guts of it is that Viruses change and fast!
2. The new virus must be able to infect humans and cause disease therein {otherwise who cares?} This is generally a property of being a novel virus to us, that is we have no pre-existing immunity through exposure to previous strains of the particular virus. The current H1N1/2009 strain seems to be affecting mostly people born after the mid1960s. This is possibly due to the exposure of older people to the 1967 pandemic strain of Influenza A. This is theory only at this stage. Pandemic strains kill an additional demographic to seasonal influenza (normally the young and the old) in addition to it's usual victims - those with depressed or inadequate immune function. Another cause of mortality is called a 'cytokine storm'. In effect it is a healthy bodies extreme reaction to a pathogen that is so over the top it attacks healthy cells as well. This is why many victims in 1918 were healthy people between age 18-45.
3. It must be easily transmissible and able to reproduce successfully within humans. Virus is transmitted in two ways. Aerosolisation - someone coughs or sneezes and you inhale their nasal secretions, mucus etc .. pretty yucky eh?
Contact transmission - they contaminate a surface, you then touch it and then touch your face (nose/mouth/eyes) and self infect. BTW a virus can remain inert on a surface for days! The best way to avoid infection is get no closer than about 6 feet to someone and the main one is to practice good hygiene (wash your hamds well and often) and stop touching your face!
Pandemics are different every time. The received wisdom is that they come in waves of some weeks. Each wave more deadly than the first. 1918 started as a relatively mild Flu and got steadily worse. Towards the end there is anecdotal evidence of people being asymptomatic as they get on the bus to go home and dead just hours later. Another danger of flu is you are contagious for up to 48 hrs BEFORE becoming ill and for some days after you have apparently recovered. This means you can be spreading the disease around the world before you even get a temperature. Do you wonder why the WHO is taking this seriously? There is no question an Influenza A pandemic will occur. What version of Flu A it will be, when, what it will look look like and how it will affect us is a different story. So these posts are about being prepared, both with knowledge about how it happens and what each of us can do about it.
Cheers,
Brad