The current outbreak of viral pneumonia in Wuhan, a rapidly flourishing capital city of the Hubei province and the traffic hub of central China, was caused by a novel coronavirus designated 2019-nCoV by the World Health Organization (WHO).
TEM image of 2019-nCoV particles. Image credit: Zhu et al, doi: 10.1056/NEJMoa2001017.
How many people have been infected worldwide?
2,744 cases have been confirmed in mainland China, and 80 people are dead. There are full or partial lockdowns in 15 Chinese cities in an effort to limit the spread of 2019-nCoV.
There are more than 50 cases confirmed around the world, in the United States, Malaysia, Singapore, Thailand, France, Australia, and more.
The epicenter of the outbreak seems to be a seafood and live animal market in Wuhan. It was initially thought transmission had been from infected animals to those people at the market, with no or limited person-to-person spread.
However, scientists have since learnt there has been person-to-person transmission in people who haven’t visited live animal markets.
The person infected in Vietnam had not been to China at all, but was a family member of someone infected in Wuhan.
This means an animal infection has probably learnt to jump to humans (from snakes?) and then spread within our species.
Who is most at risk?
Of the cases in China, 21% have been reported as severely ill and, on earlier estimates, 3% of those infected had died.
The ages of the first 17 people who died from the virus range from 48 to 89, with an average age of 73. Thirteen (76%) were men and four (24%) were women.
Most of those who have died from the virus appear to have underlying health conditions, and we know for sure in the case of ten people whose health information has been released.
These people suffered from a range of chronic conditions, including high blood pressure (41%), diabetes (29%), stroke (18%), as well as chronic obstructive pulmonary disease, coronary artery disease, chronic kidney disease and Parkinson’s disease.
We already live among coronaviruses
Four other human coronaviruses (HCoV-229E, HCoV-OC43, HCoV-NL63 and HCoV-HKU1) cause colds, flu-like illnesses and more severe respiratory diseases such as pneumonia. Viral pneumonia is a combination of virus infection of the lungs and our body’s immune response to that damage.
There are also two more infamous coronaviruses that jumped from animals to infect human hosts: SARS (severe acute respiratory syndrome) and MERS (Middle East respiratory syndrome).
Reduce your risk of coronavirus infection. Image credit: World Health Organization.
How does 2019-nCoV spread?
Scientists don’t know where the new virus came from originally. They think it originated in animals, but testing so far has not confirmed a specific animal host.
Analysis of the genome suggests it has only recently emerged in humans. So which host were humans exposed to? And how was it transmitted to humans?
2019-nCoV seems to be a respiratory virus, given the disease primarily involves the lungs, so it’s likely to spread through the same routes as colds and flu: sneezes and coughs propelling droplets into the air or onto hands that then touch other surfaces, or by touching our eyes, nose or mouth after contact with contaminated surfaces.
Droplets of urine, feces and blood could also be infectious. Contact with these substances — directly from people while they’re infectious, or indirectly from surfaces contaminated with these body substances — could lead to infection.
This is why prompt isolation of suspected cases and good infection control practices are so important, especially if a person turns into a ‘super spreader.’ This means they produce large amounts of virus and are unusually infectious.
Protect yourself and others from getting sick. Image credit: World Health Organization.
How infectious is the 2019-nCoV virus?
The WHO estimates the coronavirus has a reproduction number (R0) of 1.4-2.5. This means one infected person has the ability to infect 1.4-2.5 susceptible people. But this figure could be revised as the outbreak evolves.
In comparison, SARS had a suspected reproduction number of 2-5. This meant one infected person could infect up to five susceptible people.
So 2019-nCoV appears less infectious than SARS.
The risk of transmission for SARS was highest five to ten days into the illness. If people were isolated early on in their illness, after showing symptoms, they were unlikely to infect anyone else.
But one study showed it was possible to be infectious with 2019-nCoV without showing symptoms. This raises the possibility of an infected person transmitting the virus to others without knowing they’re sick.
This would make it much harder for health authorities to identify and isolate the infectious people and to control the outbreak.
Development of a diagnostic test
Chinese scientists sequenced the genome of 2019-nCoV and, within days, shared that information with the world.
This allowed researchers from Germany to rapidly develop and openly share a suite of specific nucleic acid tests that sensitively identify the virus by detecting small amounts of its RNA.
Researchers in Hong Kong and from the Chinese Centre for Disease Control then published their own different tests.
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Na Zhu et al. A Novel Coronavirus from Patients with Pneumonia in China, 2019. The New England Journal of Medicine, published online January 24, 2020; doi: 10.1056/NEJMoa2001017
Jasper Fuk-Woo Chan et al. A familial cluster of pneumonia associated with the 2019 novel coronavirus indicating person-to-person transmission: a study of a family cluster. The Lancet, published online January 24, 2020; doi: 10.1016/S0140-6736(20)30154-9
Wei Ji et al. Homologous recombination within the spike glycoprotein of the newly identified coronavirus may boost cross-species transmission from snake to human. Journal of Medical Virology, published online January 22, 2020; doi: 10.1002/jmv.25682
Authors: Sanjaya Senanayake, an associate professor of medicine and an infectious diseases physician at the Australian National University; Ian M. Mackay, an adjunct assistant professor at the University of Queensland, & Katherine Arden, a virologist at the University of Queensland.
This information was originally published on The Conversation and CNN.
