In less than a month, a virus originating from China has been gradually gaining attention as a new deadly contagion that has drawn comparisons to SARS. Reports of the virus first surfaced late last month when Chinese officials alerted the World Health Organization about a mysterious pneumonia-like illness that had infected people in Wuhan, a city of 11 million people located in central China. As of Friday morning, the pathogen, which has been identified as a new strain of coronavirus, has been blamed for causing at least 26 deaths and sickening 830 people, according to the latest update from the New York Times. The Times also reported that Chinese authorities have expanded a travel ban in central China "to include 12 cities near the center of the outbreak, effectively penning in 35 million residents — nearly the population of Canada — in an effort to contain the deadly virus." [See update on new confirmed case in U.S. below.]

Here is the latest information on the outbreak.

What exactly is a coronavirus? What are the symptoms?

First identified in the mid-1960s, human coronaviruses are a large family of viruses named after the crown-like spikes on their surface. Of the seven that have been identified to date, four are considered common and usually only result in mild respiratory illnesses, such as the common cold. But in some cases, coronaviruses infect animals and then evolve into a new human coronavirus. This is the case with the latest coronavirus, officially known as the "2019 Novel Coronavirus" or 2019-nCoV. The same was true of SARS, which also began in China and resulted in a worldwide outbreak in 2002 and 2003 with more than 8,000 cases, including 774 deaths.

Those infected with the Wuhan coronavirus have reported having a mild or severe respiratory illness, including fever, cough and shortness of breath. According to the Centers for Disease Control and Prevention (CDC), following exposure to the virus, the symptoms can emerge anywhere between 2 to 14 days.

How serious is this latest outbreak?

Dr. Nischay Mishra, a virologist and molecular biologist at Columbia University's Mailman School of Public Health, said that all outbreaks that involve human to human transmission warrant concern. He previously worked on another coronavirus outbreak known as Middle East Respiratory Syndrome (MERS), which was first reported in Saudi Arabia in 2012. But he said that compared to the pace of the SARS epidemic, which had a much higher percentage of fatalities in the early weeks, the Wuhan coronavirus has not reached the same threat level.

"It is serious," he said. "Is it SARS-level serious? I don’t think so. Not yet."

So far, the bulk of the cases and all of the deaths have been in China, which since the SARS epidemic has developed a blueprint for tracking viral infections, Mishra said.

But there have been some questions about how transparent China, which along with other Southeast Asian countries suffered a heavy economic toll as a result of SARS, has been about the outbreak. Dr. Ian W. Lipkin, director of the Center for Infection and Immunity at Columbia University’s Mailman School of Public Health in New York, recently told the New York Times, “I saw film footage of a hospital lobby in Wuhan, and they are wearing full personal protective equipment from head to toe. They are taking it very seriously. I still don’t think this is as bad as SARS, but it’s worse than they originally portrayed it.”

On Thursday, the World Health Organization (WHO) said it would not declare the outbreak a global health emergency but said it was still closely monitoring the situation. Other countries that have had cases of the disease include Nepal, Vietnam, Singapore, Japan, South Korea, Taiwan, and Thailand.

The CDC has issued a travel notice with a level 3 warning, the highest category, and recommended that Americans avoid all non-essential travel to Wuhan. Flights and trains leaving the city have been canceled, and internal transit in the form of bus, subway and ferry lines have also been suspended. On Friday, it was reported that Chinese authorities had expanded travel restrictions to cities near Wuhan.

But in a sign of heightened concern among Chinese health officials, major Chinese cities, including Beijing, are prohibiting large assemblies in advance of the coming Lunar New Year festival, which is by far the most important Chinese holiday.

Mishra said that given the large gatherings and travel, he expected that more cases would be reported following the Lunar New Year.

Has the disease reached the United States?

Yes. On Tuesday, an unnamed Seattle man, described as being in his 30s, was diagnosed with 2019-nCoV after he was hospitalized for pneumonia. He had recently traveled to Wuhan. Health officials have been trying to retrace the man's steps in hopes of learning more about the virus and how it is spread. “We have our first case in the U.S.,” said John Wiesman, the secretary of health in Washington State, at a news conference on Wednesday. “I would expect that at some point we’re going to have more cases in the U.S.”

On Thursday, Texas health officials in Brazos County said they were investigating a possible case of 2019-nCoV, according to several news reports. The man, who was confirmed to be a student at Texas A&M University, had traveled to China.

Here in New York, the CDC has been administering screenings of passengers arriving at John F. Kennedy Airport from Wuhan.

UPDATE: On Friday, a second case of the Wuhan coronavirus was confirmed in Chicago by the CDC and Chicago health department officials. According to the Chicago Tribute, the woman is in her 60s and is now in stable condition at a hospital.

How is the disease transmitted? Are some people more vulnerable?

The CDC has said that it not clear yet how easily the Wuhan coronovirus spreads from person to person. Early on, a link among the infected to a large seafood and animal market had suggested animal-to-person spread, but the spread of the illness has shown patients who have not had contact with animal markets. The source of the latest coronavirus is still unknown, although some have speculated that it could have started with bats, which were also believed to be the original hosts for SARS.

Early indications are that older individuals and those with weakened immune systems are at greater risk of developing more serious symptoms from the virus. A Times story reported that an examination of Chinese information showed that most of those who have died from the disease have been older men, many with underlying health problems. But on Friday, the news website reported that the youngest victim was identified as a 36-year-old man who suffered a cardiac arrest.

Is there a vaccine? Do New Yorkers need to take any precautions?

A vaccine has not yet been developed for the latest coronavirus. But because the virus does not currently appear to be spreading in the U.S., the CDC is not recommending any additional precautions for the general public. However, it has reminded people of general good health practices like washing hands, not touching eyes, nose and mouth with unwashed hands, covering coughs or sneezes with a tissue, staying home when sick and avoiding close contact with people who are sick.

The city's Health Department has said it is working with local, state, and federal agencies in response to the coronavirus outbreak. In a press release on Tuesday, Dr. Oxiris Barbot, the New York City health commissioner, said, “At this time, the actual risk to New Yorkers is low, but our level of preparedness is high, and we are monitoring the situation daily to determine if our plans to protect New Yorkers need to be adjusted accordingly.”

Following the CDC's recommendation, the city is recommending that people who have been traveling in China seek medical care if they feel sick with fever, cough, or difficulty breathing.