During the 1990s, students, trade unionists, and other workers often demonstrated to express their growing discontent with Mugabe and ZANU–PF party policies. In 1996, civil servants, nurses, and junior doctors went on strike over salary issues. The general health of the population also began to significantly decline; by 1997 an estimated 25% of the population had been infected by HIV in a pandemic that was affecting most of southern Africa.