London's FTSE 100 share index has seen one of its worst weeks since the depths of the financial crisis in 2008 as markets continue to reel from the impact of the coronavirus.
Shares have shed almost 13% of their value, wiping £210bn from the value of companies on the index.
Investors are worried after a surge in the number of companies warning about the impact of the outbreak on firms.
US markets are also in the red, with markets around the globe in retreat.
"The panic mode is full on," said Ipek Ozkardeskaya, senior analyst at Swissquote Bank.
"The coronavirus outbreak has certainly hit businesses, and it might have a longer-than-expected negative impact on company earnings and global growth," she added.
Globally, the dismal week on stock markets has so far wiped about $5 trillion from the value of listed companies around the world, according to Capital Economics' chief economist Neil Shearing.
He said that affected the value of pension pots and could make it more difficult to borrow money if banks become more fearful of taking risks.
Why should I care if share prices fall?
Big shifts in the stock market are often in the news, whether they are booms in the US or falls due to the coronavirus or the financial crisis.
As companies grow, they issue shares. The largest companies in the UK have shares which are bought and sold on the London Stock Exchange.
There are good reasons why this performance affects your life and finances.
Millions have pensions - either private or through work - who will see their savings (in what is known as a defined contribution pension) invested by pension schemes. The value of their savings pot is influenced by the performance of these investments.
Pension savers mostly let experts choose where to invest this money to help it grow. Widespread falls in share prices are likely to be bad news for pension savers.
Investors are selling shares over fears that consumers will spend less if the virus continues to spread in the UK, Mr Shearing said.
Instead, he said, investors are putting their money into government bonds, which are considered a safer investment.
"The markets are essentially betting on the fact that growth is going to slow the central bank is going to cut interest rates," he said.
And it could be a safe bet.
In an interview with Sky News, Bank of England governor Mark Carney warned that the coronavirus outbreak could lead to a downgrade of the UK's economic growth prospects.
One of the firms selling some shares to buy government bonds is Bowmore Asset Management.
"We've gone from risk assets into more safe-haven assets," the wealth manager's client director Charles Incledon said.
The company said that more than 130 listed firms in the UK had warned about the effects of the coronavirus on their business.
Those firms range from travel companies to drinks makers, with both British Airways owner, IAG, and Diageo, which makes Guinness, warning that the demand had been affected by the outbreak.
But Russ Mould, investment director at AJ Bell, said that the reaction of investors to the announcements by companies was becoming increasingly irrational.
"Yes, the outbreak is frightening. Yes, it's unquantifiable. But is it as bad as a traditional influenza season in the West? No."
He said it had killed fewer people in Europe than the French heatwave last year.
"I don't want to sound macabre or unconcerned about it, but it shows how stock market sentiment has shifted from being over-exuberant to having no fear at all to now having reassessed things in a more sober fashion."