AIDS caused 1,098 deaths, accounting for 72 percent of the total, according to a statement issued by the commission. Tuberculosis was the second-biggest killer, claiming 179 lives.
A total of 721,605 infectious disease cases were reported in the Chinese mainland last month, the statement said.
Among them, eight cases of cholera were reported but none of them resulted in death. Plague and cholera are categorized as Class A infectious diseases, the most serious bracket.
In addition, about 337,000 cases were identified as Class B infectious diseases. Hepatitis, tuberculosis, syphilis, dysentery and gonorrhea contributed to 93 percent of the cases in this category, the statement said, Xinhua reported.
It added that category C infectious diseases claimed 51 lives in May, with foot-and-mouth disease and mumps reported the most frequently.