Why I am concerned about the impending fall winter season of H1N1 influenza A aka "swine flu". The CDC centers disease control calls it a novel or new strain. It is also than described as triple reassortment, or wild type virus.
The importance of these descriptions as emotional and cognitive triggers are weighty.
Focusing on the wild description, it is predicated on the notion of novel virus. This is critical in terms of understanding the mutability of the virus.
Influenza viruses have persisted throughout human history partly because they are so adaptable. They are so adaptable because they mutate fairly abundantly and relatively rapidly. In addition, they persist because they don't kill off all their hosts. In the parlance of infectious disease, they don't annihilate their vectors, namely humans. If they did, they would die off.
Moreover they are particularly adaptable because we are not their only vectors and they seem to hide and mutate, and reassort themselves in pigs or swine as well as birds. Hence the concern for avian or bird influenza which has caused huge pandemic influenza fears in recent years. For good reason, mortality rates for avian or bird flu recently have been extraordinarily high, up to 80% of the people who became ill died. When mortality rates are that high, the virus has a much more difficult time passing from host to host. This is the reason why we rarely see Ebola virus even though it is horrifically fatal, because it is so efficiently homicidal, it does not get out of its outbreak zone very easily.
Circling back to the lexical category of wild type virus, this notion of wildness I think is quite accurate. Consider the analogy of wild zoo animals. These wild zoo animals often seen somehow tame and more safe because they are caged physically. This virus because it has a very strong genetic and clinical analogue, namely seasonal influenza which we see every year seems I think to the public mind relatively tamed and thereby understandable.
But like the wild zoo animals, they can be inexplicably cantankerous, aggressive and even homicidal. Insert link to chimpanzee.
Because the virus is in a fairly early and unstable version of itself, it is significantly more likely to shift and change. It is important to understand that the virus is exciting and threatening, because most humans have relatively little resistance to it. Therefore, the virus replicates very rapidly relative to seasonal influenza, because most of us have some resistance to seasonal influenza.
Basic virology
When the virus spreads rapidly, it is what we call an RNA virus and as such is relatively primitive. However primitive, it is a highly industrious, and highly efficient replicating machine. However, it is not very precise. RNA viruses use up all their energy replicating and not trying to get it just right therefore they make lots of bad copies of themselves. Other living organisms make copies, but have self-regulating mechanisms to fix themselves. Influenza viruses typically don't spend much energy trying to fix itself.
They make lots of not quite right viral copies. However, the emphasis is on lots. And in the case of novel influenza, probably the make significantly more copies faster than we would typically see in regular seasonal influenza. This is probably part of the reason why the virus is spreading quite rapidly. This also means that the virus mutates quite rapidly. It makes lots of different copies, and the ones that are effective in terms of replicating are the genetic variants that survive and pass from host to host. Lots of mutations.
Likely this virus's personality and character are in it's infancy. This has been the pattern for previous pandemic influenza outbreaks, particularly the 1918 influenza pandemic.. And when it reaches adolescence, unpredictable things can happen...
Examining, the 1918 influenza outbreak, there was a relatively mild summer outbreak and then the catastrophic fall and Winter . There was second, third, and fourth wave of infection. The wild new virus had transformed. It mutated from from being a relatively ill mannered cousin of the pedestrian and tame seasonal influenza virus to a stark raving homicidal maniac. It transformed the world. Ultimately, estimates of its wake range from 50 to 100 million people dead. We will never know. is the case in many disease outbreaks, the vast burden of human casualties came in the poorest places of the world. Then as now, it is difficult to track the dead.
The catastrophic aspect of this are not necessarily captured in this number. These kind of numbers I think, blow the mind. In general, the virus came in such brutal and horrific ways that it was like an angel of death. In some areas like Philadelphia 20 to 30% of the entire population was seriously ill always within a few days. In some Indian tribes, such a high percentage of the population became so critically ill, that there was no one left to take care of them even if they could recover. They died easily and in droves.
1918 to 1918 influenza outbreak may be something akin to a worst-case scenario, just as 1929 to 1939 a.k.a. the Great Depression may be akin to a worst-case economic scenario. But our great recession reminds us that financial pandemics are not footnotes in history. It teaches us that predictions about inherently complex and wild things are really hard.
This fall and winter I think will be really hard, even if it is hard to predict.
No comments:
Post a Comment