Clinical Latency Stage
The second stage of HIV, after acute or primary infection, is called the clinical latency stage. This period may also be referred to as chronic HIV infection. After initial infection, HIV replication eventually slows down within the body, although it never actually stops. An individual reaches a balance point during this period where HIV replication and CD4 cell death (the human immune cells that HIV infects) level off.
How long does the clinical latency stage last?
Without treatment, this period of time can last anywhere from two to 15 years or more, depending on a variety of factors. As time goes on, the HIV replication will slowly win out over the CD4 cells, leading to a significant decrease in CD4 count over time. When an individual reaches a count of 200 cells/microliter or less, they are considered to be in the final stage of HIV, AIDS (acquired immunodeficiency syndrome).1-5
The importance of antiretroviral therapy
As mentioned, without any interventions, the transition to AIDS can last roughly ten years. Some people may progress faster if they have other co-occurring conditions or a weaker immune system at the time they were infected. Some people may just have a more aggressive progression of the virus than others and may have more active HIV at their balance point. Regardless of individual factors though, the progression to AIDS can be slowed significantly by antiretroviral therapy (ART). ART involves taking a combination of medications every day to suppress HIV within the body.6
Although ART does not cure HIV, when taken exactly as directed by a healthcare professional it can extend an HIV-positive individual’s life expectancy to roughly that of an HIV-negative individual. This means that an individual taking regular ART can be in the clinical latency stage for many decades, rather than roughly two to 15 years.7
Symptoms during clinical latency
During this stage of HIV infection, an HIV-positive individual may experience no symptoms at all. This is the case for both individuals taking ART and those not taking ART. During this time, the individual may have no idea that they have the virus, even though it is very slowly destroying their immune system. This is an example of why HIV testing is important for those who may be at risk, even if they don’t feel sick.
Can HIV be transmitted during this stage?
Although the virus is significantly slowed during the clinical latency stage, it can still be transmitted from person to person. If an individual is unaware that they are HIV positive or is not regularly taking ART, they can transmit the virus to someone else; it will then enter the initial, acute infectious stage in the next person. Getting tested and taking ART as prescribed can reduce an individual’s viral load significantly (the amount of HIV in their blood).
Eventually, a person’s viral load can become “undetectable” meaning that the amount of HIV in the blood is so low, that the virus is not detected when tested. Recent research has suggested that those who achieve and maintain an undetectable viral load have virtually no risk of transmitting the virus to an HIV-negative partner.
This idea has been referred to as “undetectable = untransmittable” or “U=U”. Therefore, the risk of HIV transmission to an HIV-negative partner can be reduced when an HIV-positive partner is on ART and taking their medications as prescribed.8,9