The FTSE 100, which had risen 3pc this week, gave up 0.2pc. The FTSE 250 slipped 0.1pc, after adding more than 2pc earlier this week.
The China-linked virus has killed more than 600 people so far, including a doctor who was among the first to sound an alarm over its outbreak. Authorities continue to implement containment measures.
"There has been no particular news behind the sell-off, but profit-taking, weekend risk reduction and impending US data tonight have likely all contributed," OANDA analyst Jeffrey Halley said.
Investment platform Hargreaves Lansdown was the biggest blue-chip decliner, shedding 3pc after a discounted share sale by its co-founder and largest investor.
Burberry fell 2pc after it said the coronavirus outbreak was hurting luxury demand in key markets in the Chinese mainland and Hong Kong, and withdrew its forecast as a result.
Markets surged in recent sessions after sharp losses last week. Beijing made firm moves to shore up its economy, while upbeat economic data from the United States and reports that a drug had been developed to combat the virus, which the World Health Organisation later downplayed, helped prop up markets this week.
The FTSE 100 is on course for its best week in seven, while the midcaps are tracking their biggest gain in eight weeks.
On the data front, dealers anticipated US non-farm payrolls later on Friday, which could set the tone for some near-term bets.
"Ahead of the critical US non-farm payroll data, China trade numbers and with Wuhan coronavirus infections and deaths still climbing, booking profits and risk reduction ahead of the weekend appear to be the order of the day," Halley said.
Heavyweight oil stocks, as well as most miners and financial companies fell on the blue-chip bourse. However, insurer Admiral outperformed with a 1.4pc rise after it forecast higher annual profit.
Telecom firm Vodafone also climbed with a 2.6pc gain after Jefferies boosted its rating and price target on the stock.