The number of Wuhan coronavirus cases has passed the SARS total after just a month. Here's how the 2 outbreaks compare.

• A coronavirus outbreak that originated in Wuhan, China, has killed 170 people and infected more than 8,100 since December.
• The virus might have jumped from animals to people at a Chinese wet market where live and dead animals were being sold.
• SARS was also a coronavirus, and that outbreak started in a wet market, too. It killed 774 people and infected 8,098 between November 2002 and July 2003.
• The total Wuhan coronavirus case count has surpassed that of SARS in just a month. It seems to be more contagious but less deadly than SARS.
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At least 170 people have died from a coronavirus outbreak that started in Wuhan, China, and at least 8,100 have been infected across 20 countries.

The spread of this new virus, which is marked by fevers and pneumonialike symptoms, conjured a sense of déja vu for some who remember the severe acute respiratory syndrome (SARS) outbreak that started in November 2002. That was also a coronavirus, and it jumped to people from animals in wet markets, which the new coronavirus probably did, too.

SARS emerged in Guangdong and infected 8,098 people over the course of eight months, killing 774. Patients experienced fevers, headaches, and a type of deadly pneumonia that could cause respiratory failure. Experts called SARS "the first pandemic of the 21st century," since it spread across 29 countries. The disease hasn't been seen in humans since July 2003.

Less than one month after the first confirmed case of the novel coronavirus, the total case count in the current outbreak has already surpassed that of SARS.

But former FDA commissioner Scott Gottlieb told CNBC on Friday that the new coronavirus appears to be less severe than SARS even though it's more contagious.

Here are some of the crucial differences between this outbreak and the SARS one 17 years ago.

The first report of the Wuhan coronavirus came on December 31. Wuhan is a city of 11 million people in the central province of Hubei, China.

SARS originated in the Guangdong province in southeastern China, near Hong Kong.

According to the World Health Organization (WHO), 50% of people impacted by SARS were age 65 or older, while the other half of infected patients varied widely in age.

So far, one study of 41 Wuhan coronavirus case reported that the median age of those who have died is around 75. Many of those individuals had other health issues like high blood pressure, diabetes, and Parkinson's disease.

A second study of 99 coronavirus cases, published Thursday in the journal The Lancet, revealed that the average age of infected patients was 55.5. 

Adrian Hyzler, chief medical officer at Healix International, told Business Insider that children, elderly people, pregnant women, and those who are immuno-compromised are more susceptible to the coronavirus' most severe complications.

The new coronavirus has spread far faster than SARS did.

It took eight months for SARS to spread to more than 8,000 people. The Wuhan coronavirus infected at least 8,100 people in just 30 days.

Ma Xiaowei, minister of China's National Health Commission, said the coronavirus' incubation period ranges from one to 14 days, the South China Morning Post reported. The illness can jump between people before patients show symptoms, which makes it challenging to control the virus' spread. SARS' average incubation period, by comparison, was seven days.

According to a study by Chinese researchers in Hong Kong, one person with the new coronavirus can pass it to three to five others — a statistic called the virus' R0 value.

The authors of the study, which has not yet been peer-reviewed, said their results suggest the coronavirus has the potential to spread globally.

WHO researchers, however, estimate that the coronavirus' R0 value is lower: between 1.4 and 2.5 people. 

The new coronavirus' fatality rate has not yet been determined with accuracy, but it seems to be around 2% so far. SARS was more deadly, with a fatality rate of 9.6%.

According to the new study in The Lancet, however, the fatality rate among the 99 coronavirus patients studied was about 11%.

At this phase of the SARS outbreak (one month in), only five people had died.

On Thursday, the World Health Organization declared the coronavirus outbreak a global public-health emergency.

SARS did not get this designation because it has only been around since 2005. Since then, it has been used five other times.

However, the Wuhan coronavirus, unlike SARS, isn't considered a pandemic yet.

One reason SARS spread to so many places around the world is that Chinese authorities initially attempted to hide the outbreak from the WHO.

The Chinese government didn't inform the WHO about SARS until February 14, 2003 — 88 days after the first reported case. According to The Sydney Morning Herald, doctors in Beijing were ordered by authorities to hide SARS patients from WHO officials during inspections.

During the initial stages of that outbreak, the Chinese government also concealed information from the public, which exacerbated the spread of disease. 

Liu Heng, an adviser to China's cabinet, told Reuters that this time around, China announced the outbreak to the public much more immediately.

"We are doing much better now ... We are paying greater attention to preventing the epidemic," he said on January 22.

Chinese public-health experts also worked to quickly share the new coronavirus' genetic information with researchers around the globe.

"The speed with which this virus has been identified is a testament to changes in public health in China since SARS and strong global coordination through the WHO," Jeremy Farrar, an infectious-diseases specialist who worked on combating SARS, told Reuters.

By contrast, it took four months for SARS' genome to be published.

By sharing information about the new coronavirus genome, scientists have been able to work together to analyze how the illness is spreading and mutating.

That work also helps experts track down which animal the coronavirus jumped from.

In the case of SARS, and probably this coronavirus outbreak too, bats were the original hosts. They then infected other animals via their poop or saliva, and the unwitting intermediaries transmitted the virus to humans.

"Bats and birds are considered reservoir species for viruses with pandemic potential," Bart Haagmans, a virologist at the Erasmus Medical Center in Rotterdam, Netherlands, told Business Insider.

Coronaviruses are zoonotic diseases (meaning they can jump from animals to people), so places where shoppers, vendors, and live and dead animals are put in close proximity can be breeding grounds for this kind of disease outbreak.

SARS jumped from bats to weasel-like mammals called masked palm civets, then to humans.

According to a group of scientists who edit the Journal of Medical Virology, the culprit spreading the Wuhan coronavirus could be the Chinese cobra, but that has yet to be confirmed.

An analysis showed that the genetic building blocks of the Wuhan coronavirus closely resemble that of snakes.

Researchers traced SARS to a population of horseshoe bats in China's Yunnan province. These bats lived in a cave just 1.1 kilometer from the nearest village. 

Here are five viruses that most likely came from bats and how the outbreaks compare.

Another difference between the SARS outbreak and this new coronavirus outbreak is that Chinese authorities quickly instituted travel lock-downs this time.

Authorities quarantined Wuhan on January 23, halting all public transportation, including city buses, trains, and ferries. The order prevents any buses or trains from coming into or leaving the city and grounds all planes at the Wuhan airport.

The city of Huanggang also went into lockdown on the same day, as authorities closed subway and train stations. By January 27, 14 additional cities — Chibi, Dangyang, Enshi, Ezhou, Huangshi, Jingmen, Suizhou, Qianjjiang, Xiangyang, Xianning, Xiantao, Xiaogan, Yichang, and Zhijiang — had followed suit with their own travel restrictions.

Tedros Adhanom Ghebreyesus, director-general of the WHO, said efforts to quarantine cities could help Chinese authorities control the virus' spread and "minimize the chances of this outbreak spreading internationally."

"What they're doing is a very, very strong measure, and with full commitment," Ghebreyesus said on January 22.

The restrictions affect at least 50 million people in China.

During the SARS outbreak, it took officials at least four months to institute any quarantine measures.

Anthony Fauci, a disease expert at the National Institutes of Health, told CNBC that he thinks China is "doing much better this time."

Neither SARS nor the Wuhan coronavirus has a vaccine.

"If Wuhan were to explode, a vaccine best-case scenario is three-quarters of a year, if not longer," Vincent Munster, a virologist at the Rocky Mountain Laboratories, told Business Insider.

Several companies, including Moderna, Novavax, and Inovio, have announced preliminary vaccine-development plans. But getting a vaccine to market has historically been an arduous, multi-year process (the Ebola vaccine took 20 years to make). None of the companies provided expected timelines.