When your immune system loses too many CD4 cells, you are less able to fight off infection and can develop serious illnesses, cancers, and neurological (nerve system) problems.
These are called opportunistic infections (OIs) because they take advantage of the body's weakened defenses. In other words, they take an opportunity to infect you when your defenses are down.
OIs can lead to hospitalisation and disability, and are responsible for most of the deaths in people with Aids (acquired immune deficiency syndrome).
Preventing and treatingOIs
The best way to prevent OIs is to keep your immune system as strong as possible by taking HIV medicines as soon as you know you are HIV+. This allows the immune system to do its job of controlling infections.
If your CD4 cell count falls below 200, taking appropriate medication can prevent many OIs from developing.
Effective treatment options are available in most cases if you do develop an OI.
The earlier you tell your doctor or nurse about any symptoms, the sooner you can get diagnosed and treated, and the better your chances that the treatment will work and you will make a full recovery.
After you recover, you may still need to get on-going maintenance treatment to keep the OI from coming back.
You may be able to stop prophylaxis or maintenance treatments if your CD4 cell count goes up and stays up. However, you should not stop any treatment without discussing it first with your doctor.
Where did HIV come from?
Scientists identified a type of chimpanzee in West Africa as the source of HIV infection in humans.
They believe that the chimpanzee version of the immunodeficiency virus (called simian immunodeficiency virus, or SIV) most likely was transmitted to humans and mutated into HIV, when humans hunted these chimpanzees for meat and came into contact with their infected blood.
Studies show that HIV may have jumped from apes to humans as far back as the late 1800s.
Over decades, the virus slowly spread across Africa and later into other parts of the world.
We know that the virus has existed in the United States since at least the mid- to late 1970s.
What are the stages of HIV?
HIV disease has a well-documented progression.
Untreated, HIV is almost universally fatal because it eventually overwhelms the immune system – resulting in acquired immunodeficiency syndrome (Aids).
HIV treatment helps people at all stages of the disease, and treatment can slow or prevent progression from one stage to the next.