• The virus has killed more than 259 people and infected at least 12,000.
  • Preliminary research, some of which has not been peer reviewed, suggests that 75,800 people in Wuhan alone could be infected. A study also suggests Bangkok is the most at-risk city outside of China.
  • Visit Business Insider's homepage for more stories .

Scientists are racing to learn more about a new coronavirus that has swept through China and spread across the globe.

The virus, which may have jumped from animals to people at a market in the city of Wuhan, has killed 259 people and infected at least 12,000.

The World Health Organization (WHO) declared the coronavirus outbreak a global public-health emergency on Thursday. The declaration has only been used five timessince it was created in 2005.

Scientists worldwide are trying to study the coronavirus and potentially develop a vaccine. Nature identified over 50 English-language studies on the virus published since January 12. More than 30 were published in pre-print servers without peer review, since the peer-review process can take months, and this virus is spreading quickly. A handful appeared in peer-reviewed journals, however.

"The primary benefit is probably in scientists being able to improve their work, to see what other scientists are working on, and come up with some consensus," Maia Majumder, a computational epidemiologist at Boston Children's Hospital and Harvard Medical School, told Wired . "For outbreaks especially, I think no matter how hard a journal tries to make review as rapid as possible, there's still going to be a delay."

Although it's preliminary, here's what published research has shown so far.

The new virus is the seventh known member of the coronavirus family, which also includes the viruses that cause the common cold and pneumonia.

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Other coronaviruses include severe acute respiratory syndrome (SARS) and Middle East respiratory syndrome (MERS).

Though it is spreading quickly, the Wuhan coronavirus so far seems less deadly than MERS and SARS.

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So far, the mortality rate for the Wuhan coronavirus is below 3%.

It might be more infectious than SARS, though. Studies looking at the number of people an average patient infects suggest it could range from one to five.

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Knowing how many people the average patient infects a number called the "R-nought" is crucial to understanding how a virus spreads.

So far, studies vary widely on the R-nought of the Wuhan coronavirus. Many land in a range similar to that of SARS, about two to three, including an estimate from the WHO . But some studies have placed the R-nought much higher , closer to five or six.

One peer-reviewed study estimated that 75,815 people in Wuhan have likely been infected as of January 25 nearly eight times the number of reported cases worldwide.

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The study , published Friday in medical journal The Lancet, estimated that infected people would pass the virus to two to three others, on average, meaning the infected population would double every 6.4 days.

They even accounted for the quarantine China has imposed on Wuhan and surrounding cities.

"Other major Chinese cities are probably sustaining localized outbreaks," the study authors wrote. "Large cities overseas with close transport links to China could also become outbreak epicenters, unless substantial public-health interventions at both the population and personal levels are implemented immediately."

Bangkok, Thailand, is more at risk than any other city as the virus spreads, according to an analysis by population-mapping experts.

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That's because the researchers estimated that Bangkok would receive over 1 million air travelers from China's most affected cities over a three-month period, starting 15 days before the Lunar New Year. Those Chinese cities included Beijing, Guangzhou, Shanghai, and Chongqing.

Thailand has so far reported at least 19 cases of the virus.

After Bangkok, that analysis identified Hong Kong, Taipei, Sydney, New York, and London as other high-risk cities.

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The most at-risk countries were Thailand and Japan. The US placed sixth in the researchers' ranking.

"It's vital that we understand patterns of population movement, both within China and globally, in order to assess how this new virus might spread domestically and internationally," Andrew Tatem, a professor at the University of Southampton and a study co-author, said in a press release .

Research has shown that people who are infected can spread the coronavirus before they show symptoms.

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In a letter published in The New England Journal of Medicine on Thursday, 20 doctors and researchers describe a case in which this happened.

An otherwise healthy, 33-year-old German man developed a sore throat, chills, a cough, and a fever a few days after meeting with a business partner from China in mid-January. Three days later, he felt better and went back to work.

It turned out that the German man had contracted the Wuhan virus from his business partner, who showed no symptoms at the time. When the 33-year-old went back to work with no symptoms, he infected at least two of his colleagues.

The period of time during which people carrying the virus show no symptoms, called the incubation period, probably lasts 2 to 14 days in the case of this coronavirus.

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That's the assumption that the US Centers for Disease Control (CDC) has adopted , based on the incubation period of MERS.

It's also the reason the White House gave when it announced on Friday that it will temporarily bar foreigners from entering the US if they have been to China within the past 14 days. US citizens who have been to the Hubei province of China where Wuhan is located within the prior 14 days could be quarantined for up to two weeks upon their return.

These policies, which go into effect on Sunday, are meant to prevent people from spreading the virus before they know they've been infected.

The Wuhan coronavirus seems to have originated in bats before making the jump to humans.

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Genetic analysis of samples of the virus, called 2019-nCoV, from nine patients revealed it to be closely related to two SARS-like coronaviruses that came from bats.

That study , published in the The Lancet, suggests that an animal sold at a market in Wuhan could have caught the virus from bats then passed it to humans.

One study suggested that the virus jumped from bats to snakes to humans, but other researchers said that's unlikely.

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In a peer-reviewed study published January 22 in the Journal of Medical Virology, a group of researchers in China suggested that snakes were the most likely animals to have passed the virus to humans.

Several other scientists have voiced their disagreement with the assessment, however.

"They have no evidence snakes can be infected by this new coronavirus and serve as a host for it," Paulo Eduardo Brando, a virologist at the University of So Paulo who is investigating whether coronaviruses can infect snakes, told Nature . "There's no consistent evidence of coronaviruses in hosts other than mammals and Aves (birds)."

Virologist Cui Jie, who was on a team that identified SARS-related viruses in bats in 2017, said this strain from Wuhan is clearly a "mammalian virus."

"Nothing supports snakes being involved," David Robertson, a virologist at the University of Glasgow, told Nature.

Though the coronavirus is a respiratory disease, a study that has not yet been peer-reviewed suggests it might also travel through the digestive system.

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The study , shared in the pre-publication repository biorXiv on Friday, comes from researchers at the Second Military Medical University in Shanghai. They detected an enzyme signature of the virus in cells from the small intestine and colon.

Australian researchers grew the virus in a lab outside China for the first time. It could help identify the antibodies humans produce before they show symptoms.

This video, courtesy of Dr. Julian Druce at the Victorian Infectious Diseases Reference Laboratory, shows the Wuhan coronavirus that scientists grew from a patient sample at the Doherty Institute.

The lab-grown sample could help identify people who aren't yet showing symptoms but are still infected and capable of spreading the virus.

"An antibody test will enable us to retrospectively test suspected patients so we can gather a more accurate picture of how widespread the virus is, and consequently, among other things, the true mortality rate," Dr. Mike Catton, deputy director of the Peter Doherty Institute for Infection and Immunity, said in a statement . "It will also assist in the assessment of effectiveness of trial vaccines."

"Beyond all, this global health threat teaches, once again, that it is far better to invest in preparedness to prevent, rapidly identify, and contain outbreaks at their source," Georgetown University researchers wrote on Thursday.

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In their analysis of government responses to the virus, published in the Journal of the American Medical Association, they added: "Reacting after a novel infection has spread widely (perhaps overreacting with travel bans and quarantines) costs lives, economic resources, and the well-being of millions of people currently cordoned off in a zone of contagion."

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