Public health experts around the globe are scrambling to understand, track, and contain a new virus that appeared in Wuhan, China at the start of December.

You can see where and how many cases have been reported in this map created by US researchers. So far, there have been over 9,700 confirmed cases and 213 deaths. The majority of the illnesses are in China, but cases have been reported in nearly two dozen other countries, including the US. No deaths related to the illness have been reported outside of China.

As this important story continues to unfold, The Verge will update this page with all the latest news and analysis. Our hope is to answer all your questions as people work to understand this virus and contain its spread.

Table of contents

Where did the virus come from?

At the end of December, public health officials from China informed the World Health Organization that they had a problem: an unknown, new virus was causing pneumonia-like illness in the city of Wuhan. They quickly determined that it was a coronavirus, and that it was rapidly spreading through and outside of Wuhan.

Photo by Kevin Frayer/Getty Images

Coronaviruses are common in animals of all kinds, and sometimes can evolve into forms that can infect humans. Since the start of the century, two other coronaviruses have jumped to humans, causing the SARS outbreak in 2002 and the MERS outbreak in 2012.

Scientists think this new virus first became capable of jumping to humans at the beginning of December. It originally seemed like the virus first infected people at a seafood market in Wuhan and spread from there. But one analysis of early cases of the illness, published January 24th, found that the first patient to get sick did not have any contact with the market. Experts are still trying to trace the outbreak back to its source.

The type of animal the virus originated from is not clear. One team of researchers in China published a report arguing that it came from snakes, based on the genetic code of the virus. However, scientists are very skeptical of that conclusion. Another analysis found that the genetic sequence of the new virus is 96 percent identical to one coronavirus found in bats. Both SARS and MERS originated in bats.

So is this the same as SARS?

The new virus isn’t SARS, although that also began in China. Because it comes from the same viral family as SARS, it has some similarities, but it’s an entirely new virus. However, the commonalities mean scientists and public health officials can use what they’ve learned from the past outbreak to try to stop this one.

China lied to the WHO about SARS. Are they lying about this, too?

During the SARS outbreak, Chinese officials attempted to conceal cases from WHO inspectors and limit information, both internally and externally. This time, officials quickly reported the outbreak of the new virus to the WHO, which praised their quick response and transparency in a press conference. China is also allowing a team of WHO experts to assist Chinese public health officials with the ongoing work, the organization announced January 28th.

The US Department of Health and Human Services also said China has been more transparent than they were with SARS. “The Chinese government’s level of cooperation is completely different from what we experienced in 2003,” said department Secretary Alex Azar during a press conference.

But critics and Chinese citizens are skeptical: there are concerns that Chinese officials are undercounting the number of illnesses and are classifying deaths that might have been from the virus as being from pneumonia. Wuhan police also investigated citizens for spreading what it called rumors online a few weeks ago.

(It’s important to note that China isn’t the only country known for concealing the extent of public health problems. In the US, for example, dozens of cities have concealed the amount of lead in their public water supply.)

How dangerous is this new virus?

Right now, no one knows.

It takes information about both how severe an illness is and how easily it can spread to determine how “bad” it can be. Epidemiologists often use this tool to assess new flus, for example, and guide decision-making:

Image: Centers for Disease Control

If an illness isn’t very severe (and kills only a small percentage of people), but it’s highly transmissible, it can still cause devastating effects — if something affects millions, the small percentage it kills will still be a high number of fatalities.

Researchers are still trying to understand the symptoms of the coronavirus, which have ranged from mild, like those in a cold, to severe. Around 20 percent of confirmed cases have been severe, according to the WHO. That’s 20 percent of the cases that we know about — it’s still possible that there are many more mild cases of the illness that haven’t been flagged, which would shrink the percentage of cases that are severe.

So far, the fatality rate for the new coronavirus is around 2 to 3 percent, though that could continue to change as the outbreak progresses. The fatality rate for SARS was about 14 to 15 percent. Most deaths in this outbreak have been in older people who have underlying health issues, like heart disease, hypertension, and diabetes. (That’s the same demographic who is most at risk of dying from illnesses like the flu.)

How fast is the virus spreading?

We don’t yet know how rapidly or easily the virus can spread. In China, sick people have been infecting others through person-to-person transmission since the start of January, and the WHO has reported that there have been sustained chains of people passing the virus along for at least four generations: one person got sick (probably from an animal), passed the virus to another person, who passed it to another person. People in four countries outside of China — the US, Germany, Japan, Vietnam — were infected with the coronavirus by other people, and not from direct travel to China.

Early evidence suggested that, like other coronaviruses, the virus jumps between people who are in very close contact with each other, and probably spreads when an infected person sneezes or coughs.

But Chinese officials have said that they have seen cases where people with the virus infected others before they start showing symptoms. A letter to The New England Journal of Medicine also details a case where people who didn’t feel sick appeared to infect others in Germany.

If that’s happening regularly, containing the spread of the virus will be more complicated. There’s still only limited evidence that asymptomatic people can spread the virus, though. And even if it was happening, it probably wouldn’t significantly affect the outbreak, said Anthony Fauci, director of the National Institute of Allergy and Infectious Diseases, in a press conference. “Even if there is some asymptomatic transmission, in all the history of respiratory borne illness, asymptomatic transmission has never been the driver of outbreaks,” he said. “An epidemic is not driven by asymptomatic carriers.”

The WHO says that researchers think each sick person will go on to infect, on average, between 1.4 and 2.5 additional people, though that’s only a preliminary estimate. Other teams of researchers have published their own estimates, with most saying a sick person will infect an average of around two or three people.

Those numbers are called the virus’s R0 (pronounced “R-naught”). The R0 is the mathematical representation of how well an infection might be able to spread. The higher the number, the more potentially spreadable it can be. For comparison, the R0 for SARS was between two and five. But that doesn’t mean each sick person will actually infect that many people; quarantines and other actions taken to control outbreaks of a virus can bring down the number of people a sick person infects.

I’ve been coughing. Do I have this virus?

If you haven’t recently been to Wuhan, China, or been in close contact with someone who is sick and has recently been to Wuhan, China, it’s very unlikely you have this virus. It’s totally normal to feel anxious, though — and there are ways to reduce that anxiety, like by distracting yourself with other activities, or keeping the risks in perspective.

If you live in the US, it’s far more likely that you have the flu or the common cold. It’s still flu season, and high levels of flu activity aren’t expected to die down anytime soon. (It’s not too late to get a flu shot!)

If you’re feeling sick and have been to Wuhan, China, or been in close contact with someone who has, tell your doctor about your symptoms.

How can I protect myself?

Based on what we know so far, you can protect yourself with the same measures you’d take (and should be taking) to protect yourself against the flu: wash your hands, cover your mouth when you cough, and stay away from people who are sick.

Should I cancel my trip to China?

The US State Department raised the travel advisory for China to a level 4, saying Americans shouldn’t travel to China because of the virus. Level 4 is the most severe warning issued. It applies only to areas with a “greater likelihood of life-threatening risks.” US citizens currently in China should “consider departing using commercial means,” the alert said.

How is China trying to stop the virus?

On January 22nd, officials in Wuhan shut down all transportation in the city, which is home to over 11 million people. They closed buses and subways, and canceled all flights and trains in and out of the city. The director general of the WHO applauded the decision, saying that it would help control the outbreak and slow the spread into other countries. Fifteen other cities, home to a total of 46 million people, are locked down as well, The New York Times reported.

However, other officials weren’t sure if these quarantines would be effective: “To my knowledge, trying to contain a city of 11 million people is new to science,” Gauden Galea, the World Health Organization’s representative in China, told the Associated Press. “It has not been tried before as a public health measure. We cannot at this stage say it will or it will not work.”

Major cities across the country canceled celebrations for the Lunar New Year, a huge holiday in China.

How at risk is the United States?

Until we know how easily the virus spreads, it’s hard to say how significant of an effect it could have in the United States. The CDC says the risk to people in the US is currently low.

There have been six confirmed cases in the US: one in Washington state, two in Chicago, two in California, and one in Arizona, according to the CDC. Five of the patients had recently traveled from Wuhan. One of the patients in Chicago had not traveled to China and caught the virus from his wife (the other patient in Chicago) who had traveled there.

So far, there have been 165 people under investigation for the new coronavirus in the United States. As of January 29th, 68 of those cases had tested negative. Testing is still underway for the remaining cases. The agency said it expects to have more people under investigation and to see more cases in the US as the outbreak progresses.

The CDC is conducting enhanced health screenings for all travelers from China at 20 airports across the country to identify any people arriving in the US with symptoms. Travelers are also given information about the virus and instructed to call a doctor if they start feeling sick.

How is the virus affecting businesses that operate in China?

A number of airlines, including United Airlines, British Airways, and Air Canada, are canceling some or all flights to and from China. United Airlines said their decision to do so was due to a drop in demand for those flights.

Tech companies like Apple started limiting employee travel to China even before the US State Department and CDC warned people against traveling there. South Korea’s LG banned travel to China completely, and both Facebook and Razer told employees who had recently returned from China to work from home.

Foxconn, the Taiwanese electronics company that has factories in China and makes products for tech companies like Apple, said the virus won’t impact their production. But China has officially extended the recent Lunar New Year holiday in an effort to curb the virus’ spread, which could delay normal production schedules. In a recent earnings call, Apple says it’s accounted for this uncertainty as it looks ahead to the next quarter.