A New American Epidemic: Dengue Fever

Ok, that's a bit of an alarmist and slightly misleading header - but there's frightful news out this weekend about a new influx of hemorrhagic dengue fever in Mexico. At least it appears frightful. "Hemorrhagic" is a terrifying word, giving rise to visions of ebola virus - and the idea that this exotic disease is on the US's doorstep is enough to spark fears of it crossing over. Indeed, dengue is quite at home in the Americas, contrary to popular perception that all virulent exotic diseases roost in Africa or Asia - and it has been known to cross our border into the Texas.

But let's look at the facts here: The article talks about a "600 percent increase" of dengue in Mexico. I always hate the construction that presents increases more than double in percent terms; it's illogical and not at all helpful. why not say "six-fold" or "six times"? In this case, the reporter seems to have got the math wrong: cases increased from 1,781 in 2001 to 27,000 cases in 2006. That's a 15 fold increase, not 600 percent. But of those 27,000 cases, there were only 20 deaths. That figure gives a more realistic look at the true nature of dengue, even in the hemorrhagic form - as the article mentions, properly treated, there's a fatality rate of 1 percent. That's it - and a long way from an ebola.

That's not to say that the rise of dengue infection isn't something to reckon with. But from what I've read, dengue seems less like a terrifying superbug and more of a beacon disease, one that we can face with common sense precautions; as the CDC notes, the virus takes advantage of human carelessness.

In most countries the public health infrastructure has deteriorated. Limited financial and human resources and competing priorities have resulted in a "crisis mentality" with emphasis on implementing so-called emergency control methods in response to epidemics rather than on developing programs to prevent epidemic transmission. This approach has been particularly detrimental to dengue control because, in most countries, surveillance is (just as in the U.S.) passive; the system to detect increased transmission normally relies on reports by local physicians who often do not consider dengue in their differential diagnoses. As a result, an epidemic has often reached or passed its peak before it is recognized.

So that implies that this epidemic may be already on the way out. For those who want to get past the AP article, here's the CDC's backgrounder.