SARS broke out in 2002; MERS spread across the world in 2012. Late in 2019, a third deadly coronavirus began to radiate out from Wuhan, a city of 11 million: 2019-nCoV.
Six to eight weeks after the outbreak is believed to have begun, thousands are sick across at least 10 countries, with 81 dead so far. Governments are screening airline passengers to prevent its spread; several Chinese cities around Wuhan have imposed travel restrictions as its population struggles to get good information on the illness.
It doesn’t yet have a real name; “nCoV” just means “novel coronavirus.” Naming a deadly virus is a delicate process. World Health Organization (WHO) guidelines suggest avoiding local or regional names or ones that derive from animals, for fear of causing political and economic tension with governments or industries. Stat reports that South East Asia respiratory syndrome has been rejected for its SEARS acronym, and that Chinese acute respiratory syndrome (CARS) has been nixed because it “kind of sounds stupid.”
Otherwise scientists are moving fast. The virus was isolated a week after the WHO got the first reports, and a test for it was developed in less than a month. How far it will spread, and how deadly it is, remains to be seen.
By the digits:
7: Types of known coronavirus that infect humans
35 million: Population of Wuhan and nearby cities in Hubei Province affected by a travel ban to contain the virus
774: Deaths caused by the 2002-2003 SARS (severe acute respiratory syndrome) coronavirus outbreak
858: Deaths caused by the MERS (Middle East respiratory syndrome) coronavirus since 2012
8,500-20,000: Flu deaths in the US to date for the 2019-2020 flu season, as estimated by the Centers for Disease Control
33%: Approximate share of cold-like symptoms and atypical pneumonia worldwide caused by coronaviruses each year
10%: Fatality rate of SARS
36%: Fatality rate of MERS
70%: Genetic similarity of the Wuhan coronavirus to SARS
40%: Genetic similarity of the Wuhan coronavirus to MERS
27 kilobases–32 kb: Size of a coronavirus genome
What’s a coronavirus?
They’re RNA viruses, meaning they have one strand of genetic material, and they have the largest genomes in that category. Double-stranded DNA acts like a copy editor to fix mutations; since RNA can mutate more easily, coronaviruses can adapt to infect different types of cells. That’s what makes coronaviruses zoonotic—capable of jumping from animals like civets and camels to humans.
The new coronavirus may have made the leap at a “wet market” in Wuhan, where “there’s a lot of skinning of dead animals in front of shoppers and, as a result, aerosolizing of all sorts of things,” writes infectious disease specialist Emily Landon. “It’s actually how SARS, another coronavirus, started in 2003.”
Four of the seven types of human coronaviruses merely cause common colds; they’re the second most common cause after rhinoviruses. The SARS outbreak in 2002 was the first coronavirus found to be potentially lethal to humans, though their risks to other animals have been known for 90 years. MERS, or Middle East respiratory syndrome, was the second such coronavirus, and deadlier; the new Wuhan coronavirus is the third, and we don’t know yet what the fatality rate will be.
The family gets the name from its distinctive crown shape, a circle with protruding “spikes.” Those spikes are glycoproteins, which bind to the target cells in the host and begin the invasion. SARS targets lung cells, one reason it’s so much deadlier than the common-cold coronaviruses, which thrive in the upper-respiratory tract. MERS seems to do the same.
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~8100 BC: The common ancestor of all coronaviruses emerges, according to molecular clock analysis.
1931: Schalk and Hawn describe an avian infectious bronchitis virus in chickens.
1937: Beaudette and Hudson isolate infectious bronchitis virus from chickens.
1946: Doyle and Hutchings find a coronavirus in pigs.
1965: Tyrrell and Bynoe from the UK’s Common Cold Research Unit (pdf) cultivate “a novel type of Common-cold virus,” HCoV-OC43, the first isolated human coronavirus.
1966: Dorothy Hamre and John Procknow discover a new virus in the human respiratory tract, HCoV-229E.
2003: SARS-CoV is identified as the cause of a massive outbreak that began the year before.
2004: HCoV-NL63, the fourth human coronavirus to be found, is isolated from an infant in Holland.
2005: A fifth is discovered, HCoV-HKU1, in Hong Kong.
2012: MERS-CoV is identified in Saudi Arabia.
Early-mid December 2019: The Wuhan outbreak likely begins.
Dec. 31, 2019: The World Health Organization is informed of a “pneumonia of unknown cause” in Wuhan, China.
Jan. 3, 2020: 44 cases of the unknown pneumonia are reported in China.
Jan. 7, 2020: Chinese authorities isolate a new coronavirus as the cause of the ongoing outbreak.
Xinhua reports that initial research indicates that the Wuhan coronavirus “is quite close to the groups of SARS and SARS-like coronaviruses, with the bat coronavirus HKU9-1 as the immediate outgroup. It is likely these coronaviruses share a common ancestor resembling the bat coronavirus HKU9-1.”
The odds are good. Bats are a natural “reservoir” for coronaviruses: “over 200 novel coronaviruses have been identified in bats and approximately 35% of the bat virome sequenced to date is composed of coronaviruses.” When researchers recently trapped tens of thousands of bats across the globe, 10% carried a coronavirus, compared to 0.2% of the other animals in their sample; they estimated that bats could carry over 3,000 different coronaviruses worldwide.
SARS originated in bats, and that’s the theory for MERS; HCoV-229E, the second human coronavirus discovered, also seems to have originated in bats. The flying mammals are notorious for the diseases they can harbor, including Ebola, Marburg, rabies, Lassa, and hantaviruses.
Why bats? It’s a tough question. Scientists aren’t actually sure if bats are more capable of hosting deadly viruses than other mammals, or whether we find a lot in them because that’s where we go to look, due to their large numbers, mobility, and proximity to humans. But recent preliminary research suggests bats may have well-tuned immune systems that keep viruses in check—rather than working to eliminate viruses, their bodies coexist with them. One theory is that it’s an adaptation to flight, giving them a “dampened” autoimmune response so the metabolic stress of staying airborne doesn’t cause an overwhelming response.
Combatting a potential plague
It took several months for scientists to figure out that SARS was a coronavirus. This time it took a week to isolate and identify; the US Centers for Disease Control has already developed a test. What changed? The technology has gotten much faster—it now takes just 48 to 72 hours to sequence a coronavirus. An AI health-monitoring startup picked up on the outbreak shortly after it began. But experience and practice also helps.
Information about the virus is spreading through a foundation of public-health networks. “China learned an awful lot from SARS [in 2003],” Eric Blank, chief program officer of public health at the Association of Public Health Laboratories, told Quartz. “They didn’t really meet their commitments and they were called out on it.”
But there’s still work to be done about how information about the virus spreads within China. For Quartz, Echo Huang details how the country’s citizens have (and haven’t) been informed. During the SARS outbreak of 2002-2003, the government’s tight censorship led to a frenzy of misinformation. The country has received some praise for greater transparency this time around, but it has also censored discussion on the billion-user platform WeChat. Users are questioning whether the government is being straightforward with information, increasing mistrust in authorities at a time when it’s most critical.
Getting people to take necessary precautions without triggering unnecessary panic is a delicate matter under the best conditions. In 2009, during the H1N1 “swine flu” outbreak, the director-general of the WHO, Margaret Chan, chose not to call it a “pandemic,” though appropriate technically, because of the resonance of the word.
China has implemented unprecedented internal travel restrictions this time around, but in Vox, Julia Belluz and Steven Hoffman find little evidence they work. A 2014 review of the literature in the Bulletin of the World Health Organization found they have “limited effectiveness in the prevention of influenza spread, particularly in… high transmissibility scenarios”; travel restrictions over 90% had the only meaningful effect, which “might delay the spread and peak of pandemics by a few weeks or months.”
As the coronavirus spread, the game Plague Inc. topped the charts in China’s iOS store as of Jan. 22.
David Tyrrell was the first person to isolate a coronavirus, part of his lifelong quest to understand, and possibly cure, the common cold. (What he found instead was that there are far too many viruses, many isolated by Tyrrell himself, that cause what we think of as a “cold” to cure it.)
Tyrrell did his work at the UK’s Common Cold Research Unit, which became famous in the country for how it pitched itself to the 20,000 volunteers studied there over 44 years: a “cheap and comfortable holiday” with “a one in three risk of catching a cold but in a very good cause.” Wellington boots were provided for exploring the countryside at this “quaint cross between a sophisticated virology laboratory and a British holiday camp,” though if subjects encountered a local they were advised to shout “Unclean!” and hold a handkerchief to their mouth if approached.