In my work as an HIV health educator, I often hear the same questions from people who are newly diagnosed with HIV:
What's the difference between HIV and AIDS?
How long does it take to get from HIV to AIDS?
How long do I have to live?
They can be difficult to answer. But by the end of this article, you should have a better understanding of how HIV disease progresses (pathogenesis). Keep these questions in mind as we look at what is known about HIV disease.
Exposure to HIV and infection with HIV are not one and the same. You can be exposed to HIV numerous times without getting infected. But once HIV is transmitted, a series of events occurs. Acute, or initial infection, is the first stage after transmission. About three to four days after initial transmission of HIV, people experience a dramatic rise in their viral load (the amount of HIV in the blood). The virus multiplies very quickly and spreads into all parts of the body, including the lymph nodes, genital tract, and central nervous system.
During acute infection, people may have "flu-like" symptoms, such as rash and fever, but many people have no symptoms at all. Since their viral load is so high, anyone who engages in risky behavior with them (like having unprotected sex or sharing needles) has a high chance of being infected. During acute infection, people also experience a temporary decrease in their CD4 count, since these are some of the first cells HIV targets.
Soon after infection, the immune system mounts a response to HIV and starts producing antibodies to control the virus. This is referred to as seroconversion, and can take anywhere from three weeks to three months. Until seroconversion occurs, people will test negative on a standard HIV antibody test. This is called the "window" period -- the time from initial infection until the time an HIV test will come back positive. So people who think they may have been exposed to HIV should get tested no earlier than one month after the exposure. If that test is negative, another negative test at three months is needed to confirm the result.
During acute infection, the body also produces HIV-specific CD4 cells to control the virus. Unfortunately, in over 99% of people, these CD4 cells are quickly damaged and can't do their job. If they do survive (in rare cases), the immune system may be able to control HIV without medication, and the individual is known as a "long-term non-progressor." These people are being studied to find out how they are able to control HIV without treatment for 20 years or more.
After seroconversion, most people see a decrease in their viral load and a rebound in their CD4 count. The lowest point that the viral load reaches is called the viral setpoint. A high setpoint can mean faster disease progression, while a low setpoint may mean slower disease progression. Another major factor of disease progression is age -- people who are infected when they are older (over 50, for example) tend to progress to AIDS faster than those who get HIV when they are younger .
After seroconversion, the individual moves from acute infection into a chronic, or long-term infection.
The next stage in disease progression is the asymptomatic stage, meaning that people show no signs or symptoms that they are infected. They may have an undetectable viral load during this period, but an undetectable viral load doesn't mean that they can't transmit HIV -- it just means that there is so little HIV in their blood the test can't see it. The asymptomatic stage can last many years and its length will not be the same for everyone.
After the asymptomatic phase, people move into the symptomatic phase. Early symptoms like thrush (a white coating of the tongue), fatigue, weight loss, etc., may begin to appear. It's not uncommon to see the CD4 count drop by 50-100 points per year.
Once the CD4 count drops below 200, the risk of developing an opportunistic infection, or OI, increases dramatically. An OI is an infection that takes the opportunity of a weakened immune system to cause a serious illness. Bacteria and viruses that are normally controlled by the immune system can now lead to life-threatening conditions. When the CD4 count drops below 50, it becomes very difficult to continue living without treatment, and the risk of death is high.
Time to AIDS
People often hear that people with HIV will progress to AIDS within ten years. But that's not always the case. While it's true that the median time from infection to an AIDS diagnosis is ten years, that's not the same as an average. A median is the number in the middle of a range of values. That means half will be lower and half will be higher, but most will be near the middle.
The above graph shows that HIV infection takes 10 years to progress to AIDS in the largest number of people. But that doesn't apply to everyone. Some people will get an AIDS diagnosis sooner and some will take much longer. In other words, there is no way to say how long it will take for an individual to progress to AIDS. Studies that have followed people with HIV for over two decades have found that 99% of them will eventually progress to AIDS if they don't take HIV drugs at some point.
What Is an AIDS Diagnosis?
A person with HIV receives an AIDS diagnosis when he or she develops one or more of the 23 OIs and other conditions listed by the Centers for Disease Control, or has a CD4 count of less than 200 or a CD4% below 14. The time between asymptomatic infection and an AIDS diagnosis is called the incubation period. During this time, people usually see their viral load rise and CD4 count drop. The result, if left untreated, will lead to an immune system that is ineffective at recognizing and fighting many other germs.
The good news is that treatment can usually bring even very low CD4 counts back up, to varying degrees. Many people with AIDS who have seen their CD4 go back above 200 after treatment ask, "Do I still have AIDS?" The answers is yes -- the CDC currently lists AIDS as a lifelong diagnosis, though this may change as the long-term benefits of treatment are proven.
Remember those three questions I listed at the start of the article? I hope you can answer them now.
Jack Denelsbeck is an HIV Health Educator at ACRIA.