The Stakes:

We are in the midst of an epidemiological crisis of our own making. Climate change alters movement and home range for a myriad organisms. Our transport of people and goods carries countless pathogens around the globe. Both events bring isolated species into sudden contact; parasites and diseases find themselves surrounded by naïve and vulnerable new hosts. And so maladies literally unknown only two or three decades ago — AIDS in humans, Ebola in humans and gorillas, West Nile virus and Avian Influenza in humans and birds, chytrid fungi in amphibians, distemper in sea lions — have today become almost commonplace. Pathogens encounter new hosts with no resistance and no time to evolve any. In such a world— in this world— so-called emerging infectious diseases (EIDs) are not just possible. They are inevitable. They are ongoing. A week scarcely passes without news of some freshly-discovered strain of influenza trading up to a human host.

In one sense, this is nothing new. The rules have not changed. Our African ancestors played out a similar scenario over a million years ago, when they moved from forest to savannah. Adopting a predatory lifestyle, sharing prey with grassland carnivores, humans acquired tapeworms previously found only in hyenas, large cats and African hunting dogs. They carried their pathogens with them when they left Africa; those pathogens, in turn, colonised native hosts in new environments, just as native pathogens took up residence in the newly-arrived humans. Agriculture and urbanization brought people and animals into even closer contact, made infection and transmission easier than ever. Fully one third of human-parasite relationships are rooted in host-switching events that occurred over the past several million years, when our ancestors expanded into new frontiers. If doctors had existed in those times, they would have remarked on a worrisome surge in the number of EIDs.

The present proliferation of EIDs is, therefore, a medical issue only in the most superficial sense. It is more fundamentally an ecological issue, an inevitable and predictable consequence of separated species brought into close contact. The only real difference is one of degree; since human activity accelerates the rate of these introductions, outbreaks now occur more frequently — and involve a greater number of host-switching events — than ever before.

There is a tendency to treat such outbreaks as isolated (if increasingly common) events, things that can only be reacted to after the fact. If this were true— if EIDs were, in fact, rare occurrences— a crisis-response approach might be cost-effective. But what we perceive as a recent development is merely the latest and most drastic iteration of a long-standing ecological principle. What we regard as a succession of crises is, in reality, the new status quo. We must stop reacting and begin preventing. We must replace ignorance with information. We must heed the sports adage: Never change a winning game, but always change a losing one.

We are losing this game. We allocate massive resources to EIDs which have already made themselves known, while virtually ignoring the far greater threat posed by those still waiting in the wings. The question now is whether we will continue to react to outbreaks case-by-case, or develop a more proactive strategy.

The question is whether we find them before they find us.
 
 

Good News, Bad News:

You will find no public health advisories about Lyme Disease in Costa Rica. On the face of it, this is perfectly reasonable; Lyme Disease has never been reported there, and none of the local tick species is known to carry the bacterium that causes it.

Some of those ticks, however, are closely related to those in other regions which do carry that bacterium, and many pathogens are able to infect a far greater range of species than they actually do; simple isolation is the only thing that keeps them from reaching their true infectious potential. Thus, while Costa Rica is free of Lyme Disease at present, potential vectors already occur in abundance there. In other words, the infrastructure for an outbreak is already in place: a single asymptomatic tourist may be all it takes to loose this painful, debilitating disease on the local population.

We know this thanks to a recent inventory of parasites from northern Costa Rica. Armed with this knowledge, we can anticipate and prepare for— perhaps even prevent — outbreaks of Lyme Disease in that region. That's the good news.

The bad news is that the Costa Rican parasite inventory is the only one of its kind ever undertaken. To a great extent, we have no idea what else is waiting to jump out at us in the world's so-called "undeveloped" areas. Over half the planet's species can be described as parasites or pathogens of some kind — and unless our knowledge of these organisms is substantially greater than our knowledge of other species, twenty percent of them at most have been documented. The remaining eighty or ninety percent remain utterly unknown, posing potentially grave threats to people, wildlife, crops, and/or livestock.

It is a truism that anticipating a problem is more time- and cost-effective than responding to one. Yet it is impossible to prepare for a threat whose very existence is unknown. This is precisely our predicament when dealing with emerging infectious diseases. Today’s EID crisis, therefore, stems directly from a fundamental ignorance about the biosphere: we simply don't know what's out there. Undiscovered pathogens and their vectors lurk beneath our feet like evolutionary land mines as we move into novel habitats, translocate species, and alter ecosystems.

What can be done?