By 0919 GMT, the pan-European STOXX 600 index was down 1.1pc after gaining for two straight sessions and recouping a small portion of the almost 4 trillion the pandemic has knocked off share values since mid-February.
Italian and Spanish bourses fell between 0.7pc and 1.5pc as the number of fatalities from COVID-19 in Italy topped 7,500, while those in Spain rose beyond 3,400, exceeding the total death toll in China.
"We've had a few days of recovery in prices, but we are unlikely to see a sustained recovery until we get a sense that the pandemic is under control in most countries," said Simona Gambarini, markets economist at Capital Economics in London.
As new cases show little signs of peaking, Europe's disease control agency said every country in the bloc was forecast to run out of intensive care beds by mid-April.
The benchmark European index has lost more than a quarter of its value since hitting a record high last month in one of the sharpest selloffs on record, and analysts expect more wild swings as nationwide lockdowns bring business activity to a grinding halt.
"Until there is light at the end of the tunnel that, at some point, those measures that are restricting economic activity will be lifted, we might see some ups and downs (in equity markets)," Gambarini said.
German shares fell 1.5pc as a survey showed consumer morale in Europe's biggest economy tumbled to its lowest level since 2009.
Tuesday and Wednesday's sessions had added up to the market's biggest two-day gain since the 2008 crash.
Other global stock markets were in similar shape as investors braced for an expected surge in US jobless claims data later in the day, with estimates ranging from 250,000 to a whopping 4 million.
"This is expected to be just the start of a streak of terrible economic data to come in the following weeks," said Hussein Sayed, chief market strategist at FXTM.
"Depending on how bad the numbers are, we may see a sell-off of the same magnitude in stocks."
Energy stocks were among the biggest decliners on the day, tracking a fall in oil prices. The sector has been among the hardest hit this month as travel restrictions and a Russia-Saudi Arabia price war hit oil demand.