TOKYO, Dec 29 (Reuters) - Japan's Nikkei average surrendered early gains and dropped more than 1.5 percent on Monday after a man was suspected of having contracted the deadly Ebola virus.

The benchmark was down 1.1 percent at 17,628.15 points by midday, after falling as low as 17,525 at one point. It had risen 0.4 percent in the morning session.

A man who returned to Japan from Sierra Leone on Dec. 23 was suspected of contracting the disease, the Ministry of Health, Labour and Welfare said.

Test results are expected on Tuesday morning. If confirmed, it would be the first diagnosis of the Ebola virus in Japan.

(Reporting By Thomas Wilson)