I finally got around to seeing the film *Contagion*, a realistic portrayal of what a serious viral pandemic would look like in our day and age. Unlike the vast majority of outbreak films, *Contagion* gets a lot of the science right. The basic reproductive number *R*_{0}, for example, makes an appearance in the film. The film’s fictional MEV-1 virus was inspired by Nipahvirus. MEV-1 has an *R*_{0} of 2-4 and a mortality rate of ~25% — severe, but realistic. Epidemiologist Ian Lipkin consulted on the film.

My favorite line is when the military asks CDC Deputy Director Lawrence Fishburne if the virus was a bioterrorist attack, like a weaponized bird flu. Fishburne reponds, “No one has to weaponize the bird flu. The birds are doing that.”

The only part I really disliked about the film is how the virus is described as “mutating” or “changing”, but never “evolving”. Unfortunately, this aspect is also a realistic description of our public health system.

Did you notice that the movie defines R0 as the basic reproduction rate? It took all the energy I could muster not to stand up in the movie theater and give an impromptu lecture on how rates have units number over time, and that R0 is a number not a rate.

Heh. I didn’t notice. I think I was holding my breath to see if she would write the equation on the whiteboard. But you’re right: biologists could stand to think more about the units of the quantities they study. I have the same issue when talking about plasmid infection “rates” instead of infection

constants. The thing that always gets me worked up is when people talk about the variance of a Poisson distribution being equal to the mean…Oh. I run around saying that the Poisson distribution has the same mean and variance all the time. Perhaps, I should add that the variance has units squared of whatever the units of the mean are. I resolve to get it right from now on! (does that cover it? or is there something else I’m missing?)

Yeah, it’s the fact that the variance has units squared of whatever the mean is. So then how can they be equal? It’s like some wierd mathematical slight of hand.