大卫•奎曼表示，这类事件变得越来越普遍，不仅是因为它们越来越经常被发现，还因为发生这类事件的机会变得越来越多。他就此撰写了一部作品，《致命接触:全球大型传染病探秘之旅》(Spillover: Animal Infections and the Next Human Pandemic）。人类与动物之间的接触一直存在，但是现代社会的发展——比如在热带雨林中修路、搭帐篷，或工厂化的畜牧方式——增加了接触的范围和频率。此外，疾病在现代社会也能传播得更远、更快。
Yet what makes MERS so scary to some, is just how much about it remains in the realm of mystery—starting with something critical: how exactly humans become infected and how they pass the virus on to others. There are clues with MERS—the sick camels, for one—but currently, bats, camels, hospitals, unprotected health care workers, unclean surfaces and politics have all shouldered a bit of the speculative blame. One Australian epidemiologist, citing “paradoxes” involved in MERS’ spread, recently even suggested that bioterrorism may have a role.
Meanwhile, two years since MERS was first discovered in humans—and now in the shadow of Ebola—the tally of patients and fatalities continues to climb. Saudi Arabia reported two new cases just last week.
The WHO has convened six Emergency Committee meetings on MERS, which by the health organization’s latest reckoning kills 35% of its victims. But while MERS has earned the carefully trained eye of the world’s medical community, it has not yet been deemed a “public health emergency of international concern.”
Even so, it has made for an unsettling state of affairs given the number of pilgrims traveling to Saudi Arabia this summer and fall. Ramadan, the peak season to perform the Umrah (a religious journey to Mecca that many Muslims make), drew more than 6 million to the country in July. And in October, many more people from all over the world will crowd into Islam’s holy city for the Hajj—a pilgrimage to Mecca that Islamic tradition requires Muslims (who are physically and financially able) to undertake at least once during their lifetimes. Some global health officials fear that, as 2.5 million additional people converge on a single city during a five-day period in October, the stage may be set to turn MERS—which is potentially one mutation away from becoming a more virulent, transmissible disease—into the world’s next pandemic.
Accordingly, scientists are scrambling to understand how a virus that had been circulating in camels for decades suddenly took root in humans and started spreading around the world.
In many ways, MERS is a familiar story, just the latest in a number of newly-discovered pathogens to have landed on the radar of public health officials in recent years. As with nearly two-thirds of emerging diseases—including HIV, SARS, H5N1 (bird flu), and H1N1 (swine flu)—MERS started making trouble for humans after a zoonotic event, or that random moment when it jumped from an animal to humans.
These events are increasingly common, both because they’re being detected more often, and because there’s more and more opportunity for such events to occur, says David Quammen, who has written a book, Spillover: Animal Infections and the Next Human Pandemic on the subject. Interactions between humans and animals have happened forever, but modern development—such as the building of roads and timber camps in tropical forest, or factory farming—has increased the scale and frequency of them. Plus disease can travel much further and faster these days.
Take SARS, or Severe Acute Respiratory Syndrome, the coronavirus that gave the world a scare in 2003 when it infected 8100 people and killed 774 of them in a matter of months.
First identified in China’s Guangdong Province in November 2002, SARS is thought to have originated in bats and been passed to humans by way of the civet, a cat-like animal that was sold in wildlife markets and eaten as a delicacy in parts of China. Once in humans, the virus spread through the air with terrifying speed and reach—most notably when it infected 321 residents of Amoy Gardens, a Hong Kong apartment complex (a 2006 paper on the outbreak found that the virus entered apartments via bathroom floor drains.) The virus ultimately traveled to more than 30 countries, helped along by a handful of “super-spreaders” or individuals who transmit disease particularly effectively. While staying in Hong Kong’s Metropole Hotel, for example, a doctor from Guangdong infected 13 people including those who carried SARS to Canada, Singapore and Vietnam.