Some analysts and economists are downgrading China's GDP growth forecast for 2020 as the coronavirus outbreak hits the world's second largest economy. Economic activity in many cities halted as factories closed for week-long Lunar New Year holidays. The break was extended in some places — a move that will hit global supply chains. Meanwhile, the service sector has also been hit as people are encouraged to stay at home. New movie launches have been cancelled during the country's peak season for consumer spending. But some have argued that Beijing's expected stimulus measures may offset the outbreak's impact on the economy. In 2019, China's full-year GDP growth was 6.1%, down from 6.6% the year before. "The immediate and most significant economic impact is in China...but will reverberate globally, given the importance of China in global growth as well as in global company revenue," said Moody's Investors Service in a report last Wednesday. On the same day, a Chinese government economist said that the country's first-quarter economic growth may drop to 5% or even lower due to the virus outbreak, Reuters reported, citing a local magazine. Here's what banks and research houses are predicting for China's economy this year.

ANZ: Maintain at 5.8%

ANZ is maintaining full-year GDP growth forecast at 5.8% for now, although it has downgraded China's first-quarter growth from 5.9% to 5.0%. "Industrial activity and exports will decrease due to a decrease in the number of working days," ANZ economists said. "Supply chain activity will be interrupted as Wuhan is a large industrial hub in central China." The economists are estimating a loss of 3.5 working days in the first quarter of 2020.

Citi: Downgrades from 5.8% to 5.5%

Citigroup economists are expecting China's full-year growth to slow from their previous forecast of 5.8% to 5.5%. They said the negative economic impact will likely be concentrated in the first quarter of the year. "Carefully calibrated policy interventions will be critical to mitigate the economic shock and maintain social stability," they added in a note.

Economist Intelligence Unit: Downgrades from 5.9% to 4.9-5.4%

The EIU said the outbreak could reduce real GDP growth in 2020 by 0.5 to 1 percentage point from its baseline forecast of 5.9% if the outbreak develops into an epidemic comparable to SARS. "The government will implement restrictions on travel and shipments, which will cause disruptions to business activity," said Imogen Page-Jarrett, a research analyst. "If the outbreak becomes an epidemic, rising expenditure on healthcare for local governments will limit room for spending in other areas," Page-Jarrett added.

An outbreak of pneumonia-like disease caused by a coronavirus was registered in Wuhan, a port city of 11 million people, the administrative center of the Hubei province, at the end of December 2019. Artyom Ivanov | TASS | Getty Images

"Plans for infrastructure building and other forms of stimulus aimed at putting a floor under economic growth this year could be put on hold." While sectors like travel, tourism and manufacturing will be the hardest hit, some sectors like pharmaceuticals, online entertainment and e-commerce may pick up. Car sales may also get a boost as consumers stay away from public transport, he said.

Macquarie: Downgrades from 5.9% to 5.6%

Macquarie downgraded its forecast for China's first-quarter GDP growth from 5.9% to 4%. It is also shaving the country's full-year GDP growth from 5.9% to 5.6% — assuming the coronavirus outbreak comes under control by the second quarter of the year, said Larry Hu, chief economist for China. "Our outlook for 2020 remains as 'getting worse before getting better,'" said Hu in a report this week, although it's still too early to assess the damage, he added. Hu said he wasn't too concerned about the loss in consumption, as any losses would be an one-off event. "For us, what's more important is the knock-on effect on property and the corporate sector," Hu said. "Especially, after four years of up-cycle, the property sector was already at a turning point even before Coronavirus hit," he said.

Mizuho: Downgrades from 5.9% to 5.6%

"Given the Wuhan virus (2019 nCoV) is exponentially more infectious than either SARS or MERS, devastation could be far more as travel, trade and economic activity face a greater scale of disruptions from larger and more transmissible outbreak," said Vishnu Varathan, head of economics and strategy for Asia. For the first half of the year, Varathan said he expects China's GDP growth between 4.8% to 5.2% before picking up to 5.8% to 6.3% for the second half due to pent-up demand.

Moody's: Maintains at 5.8%

At this time, the ratings agency is keeping its forecast of a 5.8% GDP growth for China in 2020. However, the composition of growth is likely to shift due to the impact of the virus on consumption in the first quarter that will potentially be offset by stimulus measures, said its analysts in a report last week. Even though consumption will bounce back, the recovery will not be as strong as after the SARS outbreak of 2002 to 2003, as there will be "demand destruction," said Martin Petch, a senior credit officer at Moody's Investors Service.

"I think this time around there will be some demand which has been essentially destroyed," Petch told CNBC's "Squawk Box." "People haven't traveled during Lunar New Year for example, and it's unlikely after this period of slower consumer demand that they'll double up on restaurant spending. For example, they won't go twice as many times in the coming quarters," Petch added.

Natixis: Downgrades from 5.7% to 5.5%

The immediate impact of of the coronavirus outbreak will be worse than that during the severe acute respiratory syndrome virus outbreak of 2002 to 2003 as the service sector is now China's key growth engine, said Alicia Garcia Herrero and Jianwei Xu, economists at Natixis. "Based on the SARS's experience, the service sector is likely to be more severely affected than the manufacturing sector, especially for the transportation sector, which is an important component of services," they wrote. China's economic growth is also going through a structural deceleration due to an aging population and is at the end of a long urbanization process, they added. "In other words, the coronavirus is hitting a weaker economy than was the case with SARS," they wrote.

Nomura: 'Significantly lower' than 6.1%

Nomura said that "the worst is yet to come" in the outbreak as the Chinese government acts on all front to contain the virus after its initial slow reaction. Nomura analyst Ting Lu said in an email to CNBC last week that China's annual GDP growth could be "significantly" lower than the 6.1% in 2019. The Japanese bank said that the economic impact of the coronavirus could be worse than during the SARS epidemic of 2002 to 2003.

Richard Bernstein Advisors: Fears will 'knock stuffing out' of growth

"The coronavirus is a serious issue and there is nothing positive to say about it," said Richard Bernstein Advisors, an investment firm. It was bleak on the outlook in the first half of the year. "To be frank, the attempts to contain the coronavirus and the associated public fears will knock the stuffing out of China's 1Q20 and potentially 2Q20 GDP and profits," said the firm in a note last week. Beijing will likely respond to the economic impact of the coronavirus with even more monetary and fiscal stimulus on top what what is already in the pipeline. "If the virus is contained within the next several months, then Chinese GDP could be significantly stronger than expected during late-2020 and early-2021."

Vanguard: Maintains at 5.8%

The main impact on China's economic growth is likely to be that on sentiment, said Qian Wang, Vanguard's Asia Pacific chief economist. "The good news is that the Chinese government has taken serious actions quickly," said Wang in a note. The investment advisor is maintaining its outlook for China's 2020 GDP growth at 5.8%, although the risk is clearly tilted toward the downside, she added. The viral outbreak will threaten China's growth in the near-term, but Vanguard said there is potential for a rebound in the second half of the year due to anticipated government stimulus.

UBS: Downgrades from 6% to 5.5%