a serious opportunistic infection caused by two similar bacteria (mycobacterium avium and mycobacterium intercellulare) found in the soil and dust particles. In aids, mac can spread through the bloodstream to infect lymph nodes, bone marrow, liver, spleen, spinal fluid, lungs and intestinal tract. Typical symptoms of mac include night sweats, weight loss, fever, fatigue, diarrhoea and enlarged spleen. Mac is usually found in people with cd4 counts below 100. Mac is also called mai.