July 20 (Reuters) - Myanmar politician Nyan Win, a senior adviser to ousted leader Aung San Suu Kyi, died in hospital on Tuesday after becoming infected with COVID-19 in jail, his party said, as the Southeast Asian country struggles with an exponential rise in infections. Nyan Win, 78, who had been held in Yangon"s Insein prison after being arrested when the army seized power on Feb. 1, was transferred to hospital last week, the National League for Democracy (NLD) said in a statement. Reuters was unable to reach the health ministry or a junta spokesman for comment.