Q and A

Question

How quickly does viral load drop on treatment?

I’ve been trying to understand on average, the daily rate of decrease in viral load following initial treatment.

I’m guessing that this changes over time and varies from case to case according to the chosen treatment, CD4 count and viral load level and possibly other factors.

However, supposing that the viral load is around 100,000, the CD4 count is around 400 and the treatment used is Atripla, could anyone please let me know the expected % decrease of viral load level per day at least within the 1st month of treatment?

Thank you for the help.

Answer

All HIV combinations (ART) quickly reduce viral load. ART starts working from the first dose Viral load is usually reduced by 90% (also referred to as 1 log) within the first few days. It then continues to fall but not as quickly (see below) until it becomes undetectable.

A log is a number mulitplied to the power of 10. So with a viral load of 100,000 copies/mL, a 1-log reduction would bring your viral load down to 10,000 copies/mL and a 3-log reduction would reduce it to 100 copies/mL. (See this factsheet).

You are right that individual factors will lead to difference rates of viral load reductions. These include:

  • How high your viral load was when you start ART.
  • The medicines in the combination (integrase inhibitors casuing the fastest drops).
  • The drug levels of this meds (related to adherence and how they absorb and processes drugs).
  • Good adherence – not missing doses.

UK and US guidelines recommend that your viral load should be undetectable within three months. However, many people achieve this within the first month, especailly if they are using an integrase inhibitor.

Some people take longer, especially if their viral load is very high when they start treatment.

Lots of studies have reported detailed early responses ART, including for efavirenz-based combinations like Atripla.

This decline is often referred to as having three main phases.

The first phase is very rapid – referred to in some studies as being the first few days and in others as within the first two weeks. This is where the actively infected CD4 cells are targeted. CD4 cells infected with HIV only live for a few days and when you start treatment this virus and these cells are quickly reduced.

This results in a viral load drop of perhaps 99% (2 logs) within two weeks.

The second phase, out to the first month is slower, as it is working on cells that live longer. This can easily reduce viral by another 90% (another 1 log reduction). In people with very high viral loads when they start treatment, this second phase may continue for longer until viral load becomes undetectable.

Some researchers also talk about a third phase decline which occurs even more slowly and gradually once your viral load is undetectable.

This relates to a reduction in the levels of infected CD4 cells that are latent (or resting). This pool of cells only slowly decreases over time.

This link is to a study from 2006 in people using efavirenz-based combinations. It reports an average viral load reduction of 1.9 logs after only 10 days on treatment.

This link is to an early study describing the two-phase viral load reductions.

This answer was updated in January 2016 from a question first posted on 15 September 2012.


Information on this website is provided by treatment advocates and offered as a guide only. Decisions about your treatment should always be taken in consultation with your doctor.

47 comments

  1. Hi Tom, thanks – and great that your viral load is undetectable. You need to continue taking meds though. If you stop, viral load will come back very quickly – probably within a few days and usually in less than a week

  2. Tom

    Hi, This is Tom. I am on treatment for HIV for the past two months. My viral load is undetectable. Does it mean that my HIV is cured. Can i stop my medicines. If i stop my medicines, will my viral load increase again or it will stay at the same undetectable stage.Expecting your reply soon.

  3. Hi Amanda, great that your viral load is undetectable. This means there is so little HIV in your blood to be detected in a test. You are still HIV positive though. It means that your drugs are working well and that you don;t have drug resistance. It means if you continue taking treatment this combination can work for years.

    Your CD4 count is also likely to rise. The CD4 is less important now. Your CD4 count is already good and it is likely to go higher. You have to wait for the test result though – this can’t be predicted. On average, someone starting with a CD4 count of about 450 could see this increase by anything from 50 to 200 cells in the first 6 months.

  4. amanda

    hi im Amanda. I started ART on January and my CD4 was 464 and on june the results came back as the virus is no discovered in my body (undetectable) – what does that mean? I want to know the estimate of my CD4 count to how many?

  5. zinhle

    I started treatment at a 1200 viral load and 383 cd4 count. Would like to know, how many weeks would it take for my viral load to be below 1000

  6. Hi Tif. Viral load results need to be interpreted with your history. It this is likely to be a very recent infection (with the last six months) then viral load may still go lower. If this is likely to be an infection that happened several years ago, then it is more important that you start treatment. Anything over 100,000 is considered high enough to start treatment.
    Do you know your CD4 count? This is the other test done with viral load. The CD4 count is important to know whether the fever is a symptom related to HIV.

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