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Yellow fever rolling over America

The headline of this Business Insider item reads: "MAP OF THE DAY: There's a 'Superbug' spreading around America killing 40% of the people who come into contact". The only thing missing are the 10 exclamation points that could have been added to the end of the sentence.

Unfortunately, in the mass media, this sort of sentence is quite typical.

Let's dissect the claim.

Indeed, a disease with a fatality rate of 40% is very serious, but one must stop for a second and ask 40% of what? Accidental falls are sometimes fatal but they just don't happen often enough for anyone to be worried. In the case of the new superbug, the article tells us there are 350 recent cases in Los Angeles county, which, last I checked, has 10 million residents. So, the chance of dying from this "superbug" is 140 out of 10 million, which is 0.0014% (1 in 72,000) compared to 1 in 14,000 for accidental falls.

If you have the bug, you have a 40% chance of dying. But the chance of catching the bug is miniscule. (They say "come into contact". Presumably, more than contact is needed to have the bug.)


They then show a map illustrating how this bug is "spreading around America".


If you mentally tally up the yellow area as a proportion of the whole country, you might think 2/3 of the country is an emergency zone. But this map is incredibly misleading. It is still the case that the average American would only have a 0.0014% chance of dying from the superbug. (Strictly speaking, the rate would be a tad higher in the yellow area but this distinction will go away as cases pop up in the rest of the states.)

If one were to plot a similar map for "2010 location of deaths due to accidental falls", the entire map would be yellow. The only thing missing would be the 10 exclamation points.






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With the exception of Connecticut, isn't that a map of "states with a population above a certain threshold"? (or population density, which I suppose might have an effect on spread of disease)


Don't forget that infectious diseases are not like accidental falls - diseases spread from person to person, and depending on the rate of that spread, a few hundred cases can very quickly turn into many thousands.

Also worth considering is "who is vulnerable to this disease?" The article suggests that primarily residents of long-term care facilities are vulnerable. If we suppose 1 in 1000 people are in long-term care at any given moment, and that the risk to people in the rest of the population is negligible, that 1 in 72,000 becomes 1 in 72 among the vulnerable population. To me that is significant and worthy of our attention.

Of course, this article does leave out the information we would need to draw conclusions about the rate of spread and how much of the population is vulnerable, and it is undoubtedly sensationalist with its use of the map. I guess I'm just saying that there are additional factors to consider when looking at infectious disease statistics, and it could be dangerous to fall into the trap of "this disease is rare therefore we shouldn't worry about it."


Brad: Thanks for the additional insights. I was afraid that my post might be interpreted as saying it's not a worry so it's good you bring this point up.

My point is really that our media exaggerates every risk to the nth degree using sloppy language and poor graphics, creating a society in which we fear everything and waste resources on all kinds of useless remedies.

e.g. I'm pretty sure in hindsight we massively overreacted to the bird flu scare, which sounds much worse than this particular superbug.

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