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) 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.

157 comments

  1. Lisa Thorley

    Hi George,

    Its not possible to say how quickly your viral load will drop, nor what your numbers will be. This is why in countries like the UK viral loads are tested on a monthly basis until a person becomes undetectable.

    Someone can start medication with a viral load in the millions and become undetectable within a month. Whereas its very possible that someone who starts meds with a viral load of say 90,000 may still be detectable after 4 months. What’s important is that you’re about to use medication.

  2. George

    Hello

    I am interested in daily / weekly / monthly rate of viral drop. I found only studies which were mapping the levels in the beginning and then after 48 and 96 weeks of treatment.

    I am going to start my treatment with Eviplera. If it helps, my viral load is 48 000 copies per/ml and No. of CD4 540 per/ml.

    Does Eviplera works similar to Atripla, or slower?

    Thank you so much for the answer.

  3. Lisa Thorley

    Hi Griffiths,

    Is there someone that you can talk to, a close friend perhaps or relative? Talking about the way that you’re feeling may help.

    Its common not to want to start meds. However if you want to control your HIV, you’ll need to use them. There’s more about this here:

    http://i-base.info/guides/starting

  4. Griffiths

    I have tested and I’m hiv positive and not taking any medications cause I find have the strength to face it

  5. Lisa Thorley

    Hi Candy,

    When someone’s viral load is increasing and they are on treatment, this is a sign that there may be resistance. If this is the case you’ll need to change medication. This is something that you’ll need to discuss with your doctor. Please see here for more info:

    http://i-base.info/guides/changing

  6. Candy

    Why is my viral load going high triple as it was I. M taking my treatment nicely no intercouse so what is the problem plz help

  7. Roy Trevelion

    Hi Candice, It’s good that you and your husband have started ART. As it says on this question above, viral load drops quickly at first and then drops at a slower rate. It’s great that you want to start a family soon. You can talk to the doctor about getting the timing right so that your viral load is undetectable during pregnancy. You can read more in this guide to HIV pregnancy and women’s health.

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