59 people in Wuhan, China, have been infected with a viral pneumonia. Seven of those people are reported to be in critical condition. One has died.

Officials still don't know how the disease was transmitted, though they have traced the outbreak to a seafood market that sold live animals.

Residents panicked, fearing the deadly SARS virus had returned. The last SARS outbreak ravaged China in 2003, killing 774 people. Scientists now believe the outbreak comes from the same family of viruses as SARS.

The illness has since spread to Thailand.

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Weeks before an influx of visitors are slated to travel around China for the Lunar New Year, 59 people have been infected with a mysterious viral pneumonia, and officials still don't know exactly how they got sick or what they're sick with.

Seven of those 59 people are reported to be in critical condition. With one death reported, residents of China and neighboring countries, are starting to panic, especially after a 61-year-old Chinese woman with a history of visiting fresh local Wuhan markets spread the disease while on a trip to Thailand.

Symptoms of the disease include fever, difficulty breathing and invasive lesions on both lungs, the World Health Organization reported. All of the infected patients are in quarantine, and 163 people who were in contact with the patients are now under medical observation.

Chinese officials believe the outbreak began sometime between December 12 and December 19, at a seafood market in the central city of Wuhan. The market has since been shut down.

Residents are concerned that the virus may have been transmitted from animals to humans, given that the Huanan Seafood market sold live rabbits, snakes and other animals.

Chinese researchers have shared the genome sequence with virologists all over the world, but no one has any answers yet.

Scientists think the outbreak comes from the same family of viruses as SARS

As news of a mysterious outbreak spread, residents feared that the highly contagious SARS (Severe Acute Respiratory Syndrome) virus was back. In 2003, the Chinese government initially covered up the intensity of the outbreak as SARS devastated China, killing hundreds, before spreading across Asia.

As online rumors swirled about the resurgence of SARS, Chinese officials initially announced that they ruled SARS out as a cause of illness, CBS News reported, adding that they've also ruled out bird flu and Middle East Respiratory Syndrome (MERS).

But on January 9th, Chinese scientists said they believed the outbreak came from the same family of viruses as SARS.

In 15 out of 57 patients, doctors found a coronavirus that they believed was the source of the outbreak. Coronaviruses are a family of viruses named for the way they look like coronas under a microscope, according to MedicineNet. They can cause everything from the common cold to SARS. Some coronaviruses are easily transmitted, while others are not.

This new coronavirus doesn't appear to be as deadly as SARS.

SARS was originally traced to the civet cat, which was considered a culinary delicacy in parts of Southern China, respiratory expert Professor David Hui Shu-cheong told CNN Health. It's possible this most recent virus may have been transmitted from one of the live animals sold at the market.

Countries near China have issued health warnings

Most of Asia is on high alert. The U.S. embassy released a health alert, cautioning Americans in China to "avoid contact with sick people." Health alerts were triggered across Hong Kong and Singapore, the Wall Street Journal reported. Taiwan strengthened its airport quarantine controls, according to CBS News.

"It is highly unlikely that this will lead to a major 2003-like epidemic," microbiologist Yuen Kwok-Yung told Time, "though we cannot be complacent."

This post has been updated with additional information.