The FTSE 100 looked set to end a four-day losing streak and record its best day in more than a month. The FTSE 250 firmed 0.9pc by 0845 GMT.
The new coronavirus has killed 25 people and infected more than 800 so far. While the WHO termed the outbreak "an emergency in China", it refrained from declaring it an epidemic of international concern.
FXTM market analyst Han Tan suggested dealers were also taking heart from China's efforts to lock down the epicentre of the outbreak, potentially limiting its spread and impact.
China has suspended public transport in 10 cities and a media report suggested that a hospital to treat infected people will be constructed by as soon as Monday.
Worries over the spread of the virus, which is being likened to the 2002-2003 spread of Severe Acute Respiratory Syndrome (SARS), have knocked risk sentiment this week, with the FTSE 100 on track for its worst week in seven.
"The virus itself is not the issue from an economic perspective; instead, it is the self-perpetuating negative feedback loop on economic activity that it creates," OANDA analyst Jeffrey Halley said.
Lagging the blue-chips was Just Eat, which skidded 3.6pc after Britain's competition watchdog said it would investigate Takeaway's takeover of the food delivery company.
UAE-focussed NMC Health gave up as much as 4pc after Emirates NBD Bank sold a stake in the company for about 27 million pounds, just weeks after the healthcare company was criticised by U.S. short-seller Muddy Waters.
Including Friday's losses, NMC shares have nearly halved in value since the short-seller's attack in December.
Gainers among midcaps was Virgin Money UK, which climbed 6pc higher.
The lender said Chairman Jim Pettigrew was planning to retire by September 2021.
However, Marston's slid 7pc as investors overlooked a growth in sales over the two-week Christmas holiday period and focussed on the pub operator's warning of extra costs due to a higher-than-expected rise in minimum wages.