Jo Pavey has withdrawn from Britain's squad for next weekend's World Cross Country Championships in Kenya.
Pavey's priority is to contest 10,000m at the Worlds
The 33-year-old's preparations were hit by a bout of flu which also ruined her tilt at the 3,000m at the European Indoors, where she finished seventh.
Pavey is back in training in South Africa but now wants to focus her efforts on the 10,000m.
"My top priority at the moment is getting the qualifying time for the World Championships," Pavey said.
The Commonwealth 5,000m silver medallist has not run a competitive 10,000m and does not want to leave it until the summer to attain the qualifying mark for August's World outdoors, in Japan.
Pavey will make her first attempt at the European 10k challenge meeting in Italy on 7 April, where there will be pacemakers to assist her.
Her absence from the Worlds will dent the British women's team, who claimed silver at last December's European Championships.
Britain will now be represented by five athletes in the 8km race; Hayley Yelling, Elle Baker, Hatti Dean, Felicity Milton and Kate Reed.
European cross country champion Mo Farah leads the men's team in the 12km event along with Mike Skinner, Steve Vernon, Jason Ward, Phil Wickes, Alan Buckley, Ben Noad and Phil Nicholls.