(Bloomberg) -- Shares in European companies whose businesses got a boost during past Covid-19 flareups rose on Friday as a new strain of the virus rattled markets and spurred fears of fresh social restrictions.

Virus testing companies were among the biggest gainers amid concerns about the new strain, first discovered in southern Africa. Eurofins Scientific SE, which offers PCR tests and rapid antigen tests, gained as much as 7.6%, while diagnostics peers DiaSorin SpA and BioMerieux both advanced more than 4%.

Work-from-home stocks and food delivery firms were also among gainers, with TeamViewer AG rising 4.6% and Delivery Hero SE, Just Eat Takeaway.com NV and Deliveroo Plc all advancing, even as the Stoxx Europe 600 benchmark fell as much as 3.7%. In U.S. premarket trading, Zoom Video Communications Inc. and Peloton Interactive Inc. jumped.

Today’s broad market slump “is a logical reaction, people are worried and in the right places, like travel,” said Martin Moeller, co-head of Swiss & global portfolio management at Union Bancaire Privee in Geneva, while noting gains for stay-at-home stocks. “We will learn more over time if it is more contagious or more lethal.”

So-called lockdown winners and Covid-19 testing and treatment firms had already been gaining in recent weeks as European infection rates rose. They had underperformed over the summer as vaccination programs calmed concerns around the pandemic.

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