Tropical Flu?

I would estimate that most blogs by people who think they have something to say begin with "sorry I haven't written in a while." I'm not sorry.

I work in infectious diseases. The word tropical comes up frequently. It refers to areas around the equator. It also used in phrases like "tropical disease" or "tropical medicine." Tulane has a department called tropical medicine. Of course, there is the London School of Hygiene and Tropical Medicine.

Without getting to uppity, I think it's relatively clear that this is a vestigial expression reflecting our colonial past. (Well, not America's colonial past, as we have only ever had one major colony.) The first class I took, that actually switched me from chemical engineering to public health was entitled "Invention of Tropical Disease." So, those of you who know me, yes, this is not my idea. The course discussed after the Scientific Revolution with the invention of modern science, and more importantly, new instruments. Those "haves" went around to the relative "have nots" and set about to describe them in terms of latitudes and "constitution." The British discussed the tempers and humors, while taking temperatures and being humorous. They brought disease, and brought back disease. (Look up Colombian Exchange.)

Indeed, when we think of maladies like Malaria or Yellow Fever, the idea near automatically shoots in our head of "the tropics." I don't know what it is to discriminate based on biome, but is that the case? We had malaria up through the Mississippi Valley, and Yellow Fever destroyed much of New York and Philadelphia in the 1700s. But our friends DDT and air conditioning came along. With those developments, the mosquitoes no longer bothered us, and transmission was gone.

Now these are tropical diseases...

But are we seeing the reversion back to the idea of tropical disease when describing those diseases that are most decidedly not tropical: INFLUENZA.

Lot's o talk about flu these days, as there should be. We have H5N1, H1N1, and our punctual friend, the seasonal flu. It's fairly commonly understood that flus originate in Southeast Asia, as a result of farming practices, or what have you. Travel then begins to spread it around the world, and around and around and around we go.

But there is a new theory that suggests something slightly different. Think about this: Maryland has the flu when? Like the rest of the US, in the winterish months. Why? Because we are in the northern latitudes. When does Argentina get the flu? In Maryland's relative summer. Why? Because it's in the southern latitude. What about the middle latitude by the equator? Yes. THE. TROPICS. Although they have relative peaks, they have flu near year round.

A theory from a guy named Colin Russell at Oxford came up with the Source Sink theory, which implicates the equator latitudes with their background flu as the source of our flu. Fascinating as a viroloimmunomicrobiologist. But Are the tropics getting a bad rep? Perhaps I'm overstepping the implications of calling flu a tropical disease.

Just my thought for the day.