Hong Kong (CNN Business) Chinese stocks recorded their worst day in years as investors finally got a chance to react to the worsening coronavirus outbreak .

Theplummeted 7.7% and the Shenzhen Component Index fell nearly 8.5% on their first day of trading after an extended Lunar New Year holiday. They had been closed since January 24.

The losses wiped out a combined $445 billion in market value.

China's currency also fell. The yuan sank 1.6% in onshore trading, dropping below seven to one US dollar in its first day back from the holiday break. The yuan also weakened below the seven mark offshore, where it moves more freely and has been trading since last week.

While global markets have had several days to weigh the rapid spread of the coronavirus, this is the first chance that mainland China has had to react in more than a week. Before the holiday, the number of cases numbered roughly 800 — now, there are more than 17,000.

Markets were originally due to reopen last Friday, but the Chinese government extended the holiday as it worked to control the outbreak.

Pumping money into the market

Authorities knew Monday's shock was likely inevitable. The People's Bank of China said Sunday that it would inject 1.2 trillion yuan ($173 billion) into the Chinese markets by buying short term bonds to shore up banks' ability to lend money. The measure will help maintain "reasonably ample liquidity" in the banking system and keep currency markets stable, the central bank said.

The net amount of liquidity being injected into the markets is much lower. According to Reuters calculations using central bank data, more than 1 trillion yuan worth of other short-term bond agreements will mature Monday. That brings the net amount of cash flooding into the markets down to 150 billion yuan ($22 billion).

The central bank will also keep in contact with financial institutions and markets to determine what other policy responses may be necessary, according to Pan Gongsheng, deputy governor of the central bank.

Protecting China's financial markets and economy is a top priority for the government, which is also bracing for a potentially severe hit to first quarter economic growth. Economists have said that China's growth rate could drop two percentage points this quarter — a decline that could mean $62 billion in lost growth.

Along with Monday's liquidity kick, top financial and economic regulators have announced dozens of other measures to stabilize the situation.

For example, the National Development and Reform Commission — the country's top economic planning agency — said Monday the government would "go to all lengths" to make sure that people have what they need to live, including food and other necessities. It also encouraged companies "that are key to control and prevent the virus" or are "of vital importance to the national economy" to resume production as soon as they can.

And the People's Bank of China said Saturday that it would provide money at low interest rates to commercial banks so that those banks could offer cheap loans to companies that make clinical masks, virus testing kits and other types of medical supplies. The central government will also subsidize those special loans.

The country's stock exchange regulators have also said they would allow companies to delay 2019 annual reports and 2020 quarterly earnings reports if they are affected by the disruption.

Other markets react

Markets elsewhere in Asia were mostly lower Monday, too — though their losses were not nearly as dramatic as in China.

Nikkei 225 N225 Kospi KOSPI closed down a fraction of a percent. In Japan, where 20 cases of the virus have been confirmed, thefell 1%. In South Korea, which has 15 confirmed cases, the benchmarkclosed down a fraction of a percent.

Hang Seng Index HSI Hong Kong's, meanwhile, closed up 0.2% after moving between small gains and losses. The index lost more than 6% last week after investors returned from the Lunar New Year holiday. Unlike in mainland China, Hong Kong markets reopened last Wednesday.

Dow INDU S&P 500 SPX Nasdaq Composite COMP higher during Asian trading hours. In the United States, stock futures were actually higher overnight.andfutures were all roughly 0.5% to 0.8%higher during Asian trading hours.