The natural course of HIV infection
As you learnt in Study Session 1 of this Module, an infected person may not show symptoms of the disease right away — it generally takes some time to develop a disease after an infection. Likewise, when we say someone is 'infected with HIV', we mean that the person has the virus in their blood, and this has been confirmed by doing a laboratory analysis for HIV, or a rapid diagnostic test (RDT) on their blood. Note that an HIV-infected person may not have any symptoms and may look healthy, but they can still transmit the virus to their sexual partner(s).
During the first years of infection, the immune system, although weakened by the loss of some of its CD4 lymphocytes, still functions quite well. The infected person will have no symptoms, or only minor symptoms — perhaps a little loss of weight, or inflammation of the sinuses in the head. Many HIV-infected people do not know that they have acquired the virus at this stage.
You will learn how to do the HIV rapid diagnostic test in Study Session 24 of this Module.
Over several years, the person's immune system gradually becomes weaker, and they become vulnerable to persistent communicable diseases that they would previously have fought off before symptoms even developed, or would have quickly recovered from. These diseases are called opportunistic infections (OIs) because the infectious agents that cause them only have the 'opportunity' to multiply in the body because the PLHIV's immune system has been so badly affected by HIV.
You will learn about opportunistic infections in detail in Study Session 21.
In adults, it usually takes around 5–10 years after HIV infection before the person becomes very sick, if he/she is not taking ART. The natural course of HIV infection is shorter in children and infants when compared to adults. In Section 31.1 you will learn why HIV-infected children progress faster to AIDS.
You will learn about prevention of mother-to-child transmission of HIV in Study Session 27, and about HIV in children in Study Session 28.