Despite its severity, however, there is almost nothing surprising about this pandemic. It has been utterly predictable in nearly every way: from the nature of its emergence, to its rapid international dissemination, to its clear potential to sicken people and kill them. What is surprising is the fact that we are not better prepared for this kind of assault.
As the late Nobel Prize-winning molecular biologist Joshua Lederberg put it, in what is perhaps both his most famous and his most ignored warning, viruses pose “the single biggest threat to man’s continued dominance on this planet.” As the world learned in 1918, when influenza killed at least fifty million people, there is no weapon as lethal that is also as widespread.Moreover, these viral invasions often move in obvious, specific patterns. No one who has ever glanced at a textbook on emerging infectious diseases or, for that matter, read the science section of a newspaper, could have been surprised to learn that bats were the original host of this virus, or that humans almost certainly acquired it from an intermediary species—in this case, probably pangolins, which are thought to be the most heavily trafficked animals on Earth. Pangolins are prized for the supposed medicinal properties of their scales, and they appear to have been sold at the seafood market in Wuhan where the epidemic appears to have started.
Infectious diseases that leap from animals to humans are called zoonoses. They do it all the time. Most people remember the worldwide panic caused by Severe Acute Respiratory Syndrome, or SARS, which, in 2002, led to the first pandemic of the millennium—although its global death toll was seven hundred and seventy-four people, fewer than the number of people who die in an average week at the height of an annual flu season in the United States. The SARS virus, which also originated in China, passed to humans through a protein—ACE-2, or angiotensinconverting enzyme—that is found on respiratory cells, which also serve as an entry point for the COVID-19 virus. They are both coronaviruses—named for the halo you see around them under a microscope—are genetically similar, and were isolated in bats. The same was true for MERS, or Middle East Respiratory Syndrome, a coronavirus that began in 2012 and spread through Saudi Arabia. MERS was transmitted to humans via camels, but it originated in bats, as did the Ebola virus. Marburg, a deadly hemorrhagic virus that was first described in 1967, originated in Old World fruit bats.
The reason that bats play such a significant role in the transmission of these viruses is not difficult to understand. Bats make up roughly twenty per cent of all mammal species, and many of them have unusually robust immune systems that seem easily able to defend them against powerful viruses. That makes them the perfect viral host; the viruses train themselves on the bats’ immune system, and, in the process, become increasingly able to defend themselves. Yet bats are hardly the only host of viruses that infect humans. In 2004, a highly pathogenic form of avian influenza, H5N1, which occurs naturally in wild waterfowl but can spread easily to domestic poultry, leaped from chickens to humans, setting off a frightening epidemic. In 2009, the new strain of influenza was a form of H1N1, also called swine flu, because it passed to humans through pigs; they serve as a common mixing vessel for viruses, because porcine respiratory cells are similar to ours.
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These viruses all pose special threats because they are new, which means that humans have no antibodies to defend against them.
The 2009 H1N1 epidemic infected at least 1.4 billion people, most of them before vaccines or treatments for the virus were available. And that was in a year when, by most accounts, the W.H.O. moved as expeditiously as it ever has. That strain of influenza killed as many as two hundred thousand people in the world—but it could have been many times worse. In 1957, for example, the Asian flu pandemic killed more than a million people. In 1968, the Hong Kong flu pandemic killed between one and four million. Maybe we will also be lucky this year. (It ought to be remembered that, even now, the seasonal flu poses a much greater threat to the health of the average American.) Unless COVID-19 proves to be uniquely virulent, it will likely subside within a few months, and the danger it poses will be substantially forgotten, like that of SARS, MERS, avian influenza, and other zoonotic diseases. But it is too soon to know for certain.
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At some point, not many years from now, we will have the capacity to instantly sequence viruses and to make and operate diagnostic tests anywhere, not just in a lab. Biology is becoming digital information, and it needn’t be stored only in Cambridge, or Palo Alto, or Paris. It is already possible to transmit and print a DNA sequence using the molecular equivalent of 3-D printers—a process that could enable scientists almost anywhere to construct vaccines. Making this technique readily available should be a national and, in fact, an international priority. There are other possible solutions, such as editing the genes of pigs (and bats) to repulse the viruses that can transfer to humans. This kind of ecological intervention would be scientifically difficult, and ethically questionable. But it will inevitably be discussed, so let’s do it rationally.
Even if this pandemic passes quickly, there will be another one, possibly far more catastrophic, next year, or in ten years’ time, or twenty. All we can know for sure is that if we have any hope of containing it, the time to prepare is now.
