HIV/AIDS is a global pandemic. As of 2010, approximately 34 million people have HIV worldwide. Of these approximately 16.8 million are women and 3.4 million are less than 15 years old. It resulted in about 1.8 million deaths in 2010, down from a peak of 2.2 million in 2005.
The CIA World Factbook gives the world annual birthrate, mortality rate, and growth rate as 1.89%, 0.79%, and 1.095% respectively.
As of today, it is estimated to number 7.109 billion by the United States Census Bureau (USCB).
0.79% * 7.1 bi = 56 mi deaths yearly.
If these calculations are correct this means AIDS accounts for 3.5% of yearly deaths worldwide, I don't think this counts as a "big source".
But I could be wrong...
According to the World Health Organization, the 10 leading causes of death in 2002 were:
12.6% Ischaemic heart disease
9.7% Cerebrovascular disease
6.8% Lower respiratory infections
4.8% Chronic obstructive pulmonary disease
3.2% Diarrhoeal diseases
2.2% Trachea/bronchus/lung cancers
2.1% Road traffic accidents