Kevin Patterson writes:

Wuhan, in the province of Hubei, China, is a transportation hub of 11 million built where the Yangtze and Huan Rivers meet. In December, patients began presenting, in steadily increasing numbers, with symptoms and clinical findings suggestive of viral pneumonia. (Pneumonia is an infection of the lungs; it may be caused by viruses, bacteria, or fungi.) Tests for known pathogens capable of causing such an illness came back negative. This raised the question of whether a novel pathogen—an infectious agent not previously known to affect humans—had emerged.

A person in full-body protective gear looks at his shadow on the wall, which is a robed figure in a broad hat and a plague mask with a long beak.

Novel pathogens inspire a particularly pointed sort of anxiety among doctors. Many familiar pathogens are lethal on a broad scale—influenza caused over 34,000 deaths in the US in 2018/19, for instance—but their behaviour is known and tends to be consistent. Seasonal influenza, for example, is active in the northern hemisphere beginning in November; its spread slows dramatically by late March. It is monitored carefully and understood well enough that vaccines may be prepared that are usually effective at reducing disease incidence and severity. We know how to contain this virus, we know which patients will be the most vulnerable to it, and we know, within an order of magnitude, how many will die. The ceiling on that number matters. While the best-case scenario for influenza each year includes many deaths, we also have an idea of what the worst-case scenario is. The downside risk is not infinite.

With novel pathogens, this is not true. The worst-case scenario is undefined. Novel pathogens are not inevitably virulent or necessarily prone to become epidemic, but some of them do prove to be catastrophic—and doctors don’t know, when one emerges, what course it’s going to take.

The number of ill in Wuhan grew quickly, as did the number of medical researchers paying attention. On December 31, China notified the World Health Organization (WHO) that it was seeing an outbreak of pneumonia due to an unknown agent. By January 7, Chinese virologists had sequenced the genetic structure of this new virus—which has been dubbed SARS-CoV-2 (the illness that it causes is called COVID-19)—posting it online so that researchers around the world could access it. A few days later, an apparent connection to the Huanan Wholesale Seafood Market, in Wuhan, was reported to the WHO, and the market was quickly ordered to close. On March 11, following growing transmission in countries around the world, the WHO declared COVID-19 a pandemic, which it defines as “the worldwide spread of a new disease.”

The virus was found to be part of the family of Coronaviridae, or coronaviruses: a large group of viruses that are so named because, when examined with an electron microscope, they appear studded with projections that suggest a crown. Benign instances of coronaviruses cause up to a third of common colds. A more alarming example is the SARS virus, which leapt from an unknown agent (likely bats) to civet cats and caused a multinational outbreak, killing about 10 percent of the 8,000 people it infected, and which hit Toronto, where forty-four people died of the illness. Another coronavirus leapt from camels to humans in 2012 or earlier and causes a type of pneumonia called MERS, or Middle Eastern Respiratory Syndrome, which persists in Saudi Arabia. These new coronaviruses are zoonotic: they originated in animal populations and were then transmitted to humans. Researchers concluded early on that SARS-CoV-2’s leap to humans had occurred quite recently, likely sometime last November.

The story of this pandemic is, in many ways, a story about speed. HIV circulated among humans for about six decades before it was noticed. The quickness with which science has identified this new infection and defined the genetic nature of the virus causing it is unprecedented, but this is matched by the virus itself: the rapidity with which it was observed to leap to humans and the rate at which it was seen to disseminate among us has almost no parallel in modern medicine. [Continue reading…]