Your body

Opportunistic infections

The term opportunistic infections refers to a number of illnesses, infections and conditions which occur when the immune system has been damaged by HIV. They are called ‘opportunistic’ because the things that cause them (e.g. viruses, bacteria) are often present in the body and the environment but they don’t cause serious illness in a person with an intact immune system. When the immune system is significantly damaged (for example, by HIV) these common bugs may use the ‘opportunity’ to cause disease. Opportunistic infections can be serious, causing debilitating illness or death. Generally, the risk of developing an opportunistic infection increases as a person’s CD4 count decreases.

Opportunistic infections were very common in the early days of Australia’s HIV epidemic but the effectiveness of HIV antiretroviral treatments means most opportunistic infections are not common any more. If your HIV doctor thinks you are at risk of opportunistic infections (depending on your CD4 count) they may recommend specific antibiotic treatments that act to prevent them. Opportunistic infections include a number of conditions described elsewhere on this site, including thrush / candida and herpes.

Opportunistic infections also include:

Shingles is one of the more common opportunistic infections people may experience. It is caused by reactivation of the varicella zoster virus. Anyone who has had chicken pox has been exposed to this virus. Shingles symptoms can includes skin rash, pain along nerves (usually face, chest or abdomen) and painful, fluid-filled blisters.

Pneumocystis pneumonia (PCP) is a serious infection that causes inflammation and fluid buildup in the lungs. It is caused by a common fungus. Most people have been exposed to PCP but it is easily controlled by a healthy immune system. PCP causes a type of pneumonia in people with weakened immune systems, including people with HIV who have a low CD4 count. Before HIV antiretroviral treatments, PCP was very common among people with HIV but is now far less common.

Cytomegalovirus (CMV) is an extremely common virus which can be transmitted by saliva, blood, semen and other bodily fluids. It can cause mild illnesses when first contracted although many people may never have symptoms. Once a person is infected, it does not leave the body. In patients with HIV and an extremely low CD4 count CMV can cause infections in the eye leading to blindness. It can also cause severe diarrhoea and ulcers.

Tuberculosis (TB) is a bacterial infection that attacks the lungs and can invade other organs. TB can be in your body without making you sick. If your immune system becomes damaged, the TB may become ‘active’ again, making you ill. TB usually affects the lungs, but it can also affect the brain, kidneys, spine or other organ systems. TB can cause serious health problems. Your doctor will check to see if you have ever been in contact with this infection in the past and are therefore at risk.

If your CD4 count is 200 or below, you will need to pay careful attention to any symptoms that indicate the presence of an infection. Such symptoms include persistent diarrhoea, fever, night sweats, vision loss or change, abdominal pain, enlarged lymph nodes, unexplained weight loss, shortness of breath and/or chest pain. You should report such symptoms to your doctor as soon as possible to discuss treatment options.