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The WHO has declared the new coronavirus a global public health emergency—but that doesn't mean you should panic.

Hosted by: Hank Green

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On December 29, 2019, four individuals showed up at a hospital in Wuhan, China.  All had pneumonia and worked in a particular seafood and live animal market, which was enough of a coincidence to pique the interest of local health experts.  Two days later, Chinese authorities alerted the World Health Organization of a new, potentially serious respiratory virus, and you have probably heard about this virus by now.  Here's the thing, though.  The emergence of a new disease can be a really uncertain time with a lot of unknowns and a lot of misinformation, so here is a hopefully helpful breakdown of what we do know about this new virus and why there is no need to panic.

First, while you might hear some people calling this the Wuhan virus because that's where it was first noticed, scientists no longer name diseases after people, places, or animals.  The virus doesn't actually have a formal name yet, but you will see experts referring to it as 2019-nCoV, which is simply shorthand for 2019 novel CoronaVirus.  As the name implies, it is a type of coronavirus.  That's a large family of viruses named for the crown-like spikes that cover them.  

They're common in human and animal populations and many cause mild infections.  Some strains cause the common cold, for example, but the group also includes potentially serious stuff like SARS and MERS, respiratory infections that cropped up in Asia and the Middle East in 2002 and 2012 respectively.  We know this new virus is not the same as either of those because its entire genome was quickly published in a global epidemiological database, but it can cause similar symptoms like fever and cough and like those two diseases, infectious disease experts think it jumped into humans from animals making a zoonosis or zoonotic disease.

Viruses are usually somewhat finnicky about their hosts because they have to get inside cells and that means matching up to cellular parts, sort of like having the right key for a really complex lock, but on really rare occasions, a virus can just get lucky when it finds itself inside of a new species.  

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Then, it can mutate and make itself more at home.  SARS, MERS, and the novel coronavirus all probably originated in bats, though they all took different routes to reach humans.  SARS, for example, seems to have been transmitted to humans by (?~2:26) cats, while MERS was first transmitted through dromedary camels.  The viruses likely made their way into people who came in close contact with those animals, either because they cared for them or consumed them or their products.  

Now, despite what you might have seen, we don't yet know what species passed 2019-nCoV onto us.  The genetic data for the virus was released in mid-January, so scientists are still looking for clues as to its animal host.  One paper that garnered a bit of media attention suggested the virus jumped from a snake, an idea that some people found believable since snakes are often sold at the market where people seem to first get sick, but other experts are deeply skeptical.

Coronavirus infections have only been foun in mammals and birds before, so a snake would be a pretty unusual host, and the study's evidence is pretty weak.  Plus, technically, we don't know for sure that the market was the source of the outbreak.  It seems likely given that the first four identified cases were people who worked there, but researchers were able to identify older cases when they tested saved specimens.  In any event, pinpointing the host it came from isn't really the top priority right now.

The main focus of researchers is how the virus is behaving in people.  Though the numbers change daily, there have been over 4,500 confirmed cases of the virus, almost all of which are within mainland China.  Small numbers of cases have also occurred in nearby Asian countries and elsewhere in the world, including Australia, France, the US, and Canada.  That's admittedly a lot of folks getting sick, but it's worth noting that it's still really unclear exactly how often it turns severe and how infectious this new virus really is.

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While we know there is at least some human to human transmission, we don't know how easy it is yet and just looking at one metric or another can be misleading.  For instance, a preliminary estimate from the WHO put this virus's basic reproduction number, sometimes called the Rat around 1.4 to 2.5.  This is a measure of the trasnmissability of an infection, so a value of 1.4 to 2.5 means each infected person would be expected to infect 2-ish other people once you average everything out.

That might seem really bad, after all, as some have pointed out on the internet, that's on par or higher than estimates for really bad epidemics like the 1918 flu and the 2014 ebola outbreak, and technically that's true, but it's also not the whole story, because you could just as easily say it's about the same as the seasonal flu, and an R0 by itself doesn't tell you how dangerous a disease is.  R0 is almost always based on mathematical models which can be unrepresentative of the real world at times.  Also, it assumes a completely succeptible population and can be influenced and changed by human behavior.

For example, the R0 value of ebola in West Africa is very different from the R0 value of ebola in America.  This isn't some intrinsic quality of the disease, but more to the point, it tells you nothing about how sick people get when they are infected.  It's a measure of contagiousness, not virulence, the term epidemiologists use to refer to a disease's severity.  There are infections with much higher R0 values which we don't freak out about because their fatality rates are very, very low.  Like, you probably didn't hear about the outbreak of really bad pink eye in Mexico in 2003, even though it had an R0 of 4 because, you know, nobody dies from pink eye.

Epidemiologists worry about high R0 because they indicate fast-spreading pathogens and if a pathogen infects a lot of people, then even a super low fatality rate can mean a lot of deaths, and the fact is, we do not know what this new virus' fatality rate is yet.

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SARS and especially MERS had high fatality rates, but other coronaviruses don't.  To date, experts have estimated the new virus' fatality rate to be about 3%, but even that's not likely to be accurate.  It's a back-of-the-envelope calculation based on reported cases and deaths, but the true number of infections is likely much higher, as not everyone who gets infected becomes sick enough to go see a doctor and have it confirmed, so the actual fatality rate is expected to be quite a bit lower and already, it's small compared to SARS or MERS.  

Still, it is high enough to be concerning if the virus is allowed to traverse the globe unchecked.  Luckily, it appears that countries learned from both SARS and MERS and are working together to quickly respond to this disease.  China has implemented a variety of measures to minimize the spread of the virus, including cancelling Lunar New Year celebrations in Beijing and confirmed cases in other countries are being isolated to prevent the spread.  

The rapid release of the viral genome sequences in particular has also been praised by researchers as it's let scientists around the world investigate the virus and develop precise tests to detect it and vaccines are already being planned for development and testing, so while this new virus isn't something to ignore, all out panic isn't warrented either.

For now, of course, the main concern is for people in China or those who have recently been to Wuhan or nearby areas and their close contacts.  You can, of course, still take steps to protect yourself because that will help protect you from all sorts of other diseases.  If it's anything like SARS and MERS, the virus is probably spreading via the respiratory droplets produced during coughing and sneezing.  That's the same MO as influenza viruses, so the usual measures you should take during flu season apply.  Wash your hands a lot and stay home if you feel sick and bonus, you will help protect yourself from the flu, which just FYI, is a much bigger deal in the US right now.

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We're on track for an especially bad flu season this year with over 15 million infections so far, more than 140,000 hospitalizations, and over 8,000 deaths, so if you haven't already done it, get your flu shot and don't panic about the coronavirus. 

While the emergence of a new virus can be a really intense time, infectious disease researchers around the world are on it and it's amazing to see.  Thanks for watching this episode of SciShow News.  We included some links in the description that have more up-to-date information on the coronavirus, 'cause of course, we cannot make content immediately here.  

Also, we have a real quick announcement.  The team here at SciShow has got some special episodes in the works, so we're actually going to be skipping our Saturday episodes in February.  Here's a hint: there are some field trips involved.  So we'll be six days a week instead of seven for a little bit and then we'll go back to normal.  We can't wait to show you what we've been working on.