* MSCI ACWI down nearly 9%, S&P500 in correction in 6 days

* Investors shun risk assets as coronavirus spreads globally

* Safe-haven assets in demand, U.S. yield curve firmly inverted

* Asian stock markets: https://tmsnrt.rs/2zpUAr4

By Hideyuki Sano

TOKYO, Feb 28 (Reuters) - Global share markets headed for the worst week since the darkest days of the financial crisis in 2008 as investors braced for the coronavirus to morph into a pandemic and derail world economic growth.

Hopes that the epidemic that started in China would be over in a few months and economic activity would return to normal have been shattered, as new infections reported around the world now surpass those in China.

The worsening global threat from the virus prompted investors to rapidly step up bets the U.S. Federal Reserve would need to cut interest rates as soon as next month to support economic growth.

"We don't even need to wait for economic data to see how badly the economy is being hit. You can tell that the sales of airlines and hotels are already falling by a half or something like that," said Tomoaki Shishido, senior economist at Nomura Securities.

"It is fair to say the impact of the coronavirus will be clearly much bigger than the U.S.-China trade war. So the Fed does not have a reason to take a wait-and-see stance next month," he said.

MSCI all country world index fell 3.3% on Thursday to bring its losses so far this week to 8.9%, on course for its biggest weekly decline since a 9.8% plunge in November 2008.

Wall Street shares led the rout as the S&P 500 fell 4.42%, its largest percentage drop since August 2011.

It has lost 12% since hitting a record close on Feb. 19, marking its fastest correction ever in just six trading days while the Dow Jones Industrial Average fell 1,190.95 points, its biggest points drop ever.

In Asia, MSCI's regional index excluding Japan lost 0.6%. Japan's Nikkei gave up 2.5% on rising fears the Olympics planned in July-August may be called off due to the coronavirus.

Australian shares dropped 3.0% to a six-month low while South Korean shares shed 1.4%.

"The coronavirus now looks like a pandemic. Markets can cope even if there is big risk as long as we can see the end of the tunnel," said Norihiro Fujito, chief investment strategist at Mitsubishi UFJ Morgan Stanley Securities. "But at the moment, no one can tell how long this will last and how severe it will get."

The World Health Organization (WHO) said all countries need to prepare to combat the virus as the outbreak spread to major developed economies such as Germany and France.