Feb 11 (Reuters) - Under Armour Inc on Tuesday forecast a surprise drop in 2020 revenue, saying the recent coronavirus outbreak in China would hurt sales in one of its fast-growing markets, sending its shares down 15%.

The company said the health epidemic would have a $50 million to $60 million impact on first-quarter sales.

Full-year revenue is expected to be down at a low single-digit percent from 2019, Under Armour said.

Analysts on average were expecting a growth of 4.2% in 2020, according to IBES data from Refinitiv. (Reporting by Nivedita Balu in Bengaluru; Editing by Sriraj Kalluvila;)