Jason and I saw
Contagion a few nights ago. I wanted to see it because I heard on the
It's Okay to be Smart tumblr that it was supposed to be pretty scientifically accurate, and then
an article in Scientific American reported that
Contagion is one of the best disease outbreak movies to date, at least science-wise. The quality science is due in large part to a collaboration between the film makers and
Ian Lipkin, a leading virology researcher from Columbia University. Dr Lipkin even taught the actors how to pipet! Thankfully, the movie lived up to its sciencey hype. Not only was the movie creepy and thought-provoking, it was chock full of tasty science porn. Mmmm
ribbon diagrams.
The movie focused a lot on
epidemiology- the study of the health/disease of a population. Epidemiology is the intersection of biology, sociology, and statistics. They are the people that helped figure out that there are connections between smoking and cancer, or between
caffeine and prevention of skin cancer.
(Side note: in
epidemiology it must always be stressed that
correlation is not causation, i.e. just because there
is a connection between two things doesn't mean that one
causes
the other. Epidemiology gives a foundation and justification for further
research. Like in the caffeine and skin cancer example above - epidemiology showed there was a link, and then lab research discovered
exactly what that link was.)
One of the important duties of epidemiologists is tracking the progression of diseases. Knowing where a virus originated can help figure out how it evolved and mutated to its current point, knowledge that can be paramount in the development of a vaccine. If an infectious disease is stably present in the human population it is called an
endemic. On the other hand, an
epidemic
is an larger than normal outbreak of a disease. For example, recent
rises in mumps infections are considered epidemics, while the
increase in cases of the the common cold in the winter is considered an endemic since it happens every year. When an
epidemic starts to spread across larger regions, say across continents, it is then considered a
pandemic. The outbreak of H1N1 or of HIV are considered pandemics.
How then can a seasonal, endemic virus like influenza explode into a pandemic? Many factors come into play, such as an increase in travel or break downs in public health measures. A major determinant is how viruses are able to change and adapt to better infect humans. Two mechanisms are involved:
antigenic drift and
antigenic shift. Antigenic drift is when a virus mutates in such a way that the immune system can no longer recognize it and kill it. It's like the virus is putting on a costume. Antigenic drift is the major reason why you have to get a flu shot every year - the most common strains of influenza this year will have mutated and be slightly different next year. This means that even though you got your flu shot and made antibodies against influenza this year , by next year the new influenza will be too different to be recognized by those antibodies. On the other hand, antigenic shift is when two virus mix together to form a new, hybrid virus. Antigenic shift is less common, but has the possibility of producing more dangerous viruses. If a highly infectious and deadly strain of influenza from animals mixed with a strain of influenza that was able to infect humans, you could end up with a strain that is both deadly and and highly infectious.
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An example of antigenic shift. A bird virus mixes with a human virus, making a Frankenstein-like hybrid virus.
Wikimedia commons |
Epidemiology and immunology/virology are fascinating and incredibly complex disciplines. I could chat all night about them, but I'm not sure all of you would share my enthusiasm! I hope that at least I have piqued your interest enough to check out epidemiology-based stories like
Contagion or the book
The Hot Zone by Richard Preston - both are highly recommended and full of delicious science. And once flu season is in full swing, I think I may dedicate a whole post to influenza. Thoughts?
