Every few months, it seems, an invasive virus from a distant land attacks the Americas: dengue, chikungunya and, most recently, Zika. But the pathogens that frighten me most are novel strains of avian influenza.
Nobody knows just how this virus migrated over the oceans protecting the New World in 2014. But it’s possible that another consequence of human appetites — climate change — played a role.
In the past, New and Old World birds in Beringia visited numerous ponds spread out across the tundra. But with temperatures in the Arctic rising twice as fast as anywhere else, conditions are changing rapidly, shifting the distribution of creatures and their pathogens. Historically segregated species are coming into novel kinds of contact. As birds are forced to migrate earlier and farther, feeding at new times and in new places, they overlap with other bird species in unprecedented ways that pathogens can exploit.
As health-conscious consumers in the West cut beef out of their diets and newly affluent Asians add more meat to theirs, demand for bird flesh has skyrocketed.
About half of China’s poultry trade traffics in live birds. That’s because many Chinese consumers, wary of the safety of frozen meats, prefer to buy their chickens while they’re still clucking. This creates a wealth of opportunities for new viral strains to spread and adapt to human bodies.