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A Guide to Mycobacterium avium complex (MAC)


Updated October 19, 2008

What is Mycobacterium avium complex disease?
Mycobacterium avium [MY-co-bak-TEER-ee-um A-vee-um] complex, also known as “MAC,” is the name of a group of bacteria. These bacteria can infect people who are living with HIV. Adults with HIV usually don’t get MAC disease until their CD4 count drops below 50. Because MAC disease occurs later in the course of HIV infection, it usually is not the first sickness a person with HIV gets. Most people with HIV have already been diagnosed with AIDS before they get MAC. About 20 to 30 percent of people with AIDS get MAC disease.

What are the symptoms of MAC disease?
Although MAC usually infects persons through their lungs or intestines, it spreads quickly through the bloodstream, causing widespread or "disseminated" disease. People with disseminated MAC disease can have:

  • fever
  • night sweats
  • weight loss
  • abdominal pain
  • tiredness
  • diarrhea

How is MAC disease diagnosed?
MAC disease is diagnosed by laboratory tests that can identify the MAC bacteria in samples of blood, bone marrow, or tissue.

How do people get MAC disease?
People with HIV/AIDS probably get MAC disease through normal contact with air, food, and water. MAC disease has been found in many types of animals, including birds, chickens, pigs, cows, rabbits, and dogs. MAC bacteria can be found in most sources of drinking water, including treated water systems, and in dirt and household dust. MAC disease does not seem to be spread from one person to another.

How can I avoid MAC disease?
Because MAC bacteria are found in food, water, and soil, there is no easy way to avoid them. However, there are drugs that can prevent MAC germs from causing disease. Because MAC disease occurs in people with very low CD4 counts, you should not get treatment to prevent MAC disease until your CD4 count is below 50. Your doctor will tell you when you need to begin treatment for preventing MAC disease. Drugs which can reduce your chances of getting MAC disease include:

If I have already had MAC disease, can I get it again?
Yes. If you have had MAC disease, continue to take drugs to treat and prevent further MAC disease. MAC disease is most commonly treated with a combination of clarithromycin and ethambutol [eth-AM-bu-tol], with or without rifabutin.

Source: Adapted from Brochures provided by the Centers for Disease Control, 2000.

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