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.

185 comments

  1. Roy Trevelion

    Hi Sani,

    Atripla is a safe and effective drug for HIV.

    However, it’s usual for CD4 counts to go up and down. It looks as though your CD4 count is fairly stable and within the ‘normal’ range. But you can ask for your CD4% as this can show whether there’s a real change in immune function. Please see here.

    You can talk to your doctor again about why they think your treatment might not be working. And is it possible to have the viral load test result before the 25th?

  2. Sani

    Sorry about the confusion I’m on Atripla. My cd4 count have been going up and down. Before I started medication My Cd4 was 514 then it dropped to 398 then the last test I took it was as 504. My viral load has been dropping but at a slow rate. It was at 24,000 copies before but its now at 5,000 copies when I tested 3 months ago.

  3. Roy Trevelion

    Hi Sani,
    Sorry, this sounds confusing. What meds are you taking?

    But you can try talking to the doctor who thinks the treatment isn’t working. You can also ask them what other HIV meds are available to you in Nigeria.

    It’s a good idea too to ask about your previous CD4 counts to see if your immune system is recovering.

  4. Sani

    Hello. So I the first time I started my medication after 3 months my viral load was about 24,000. They didn’t check my viral load before I commenced treatment. The next time I checked my viral load it was around 9,000 and now its down to about 5,000. The problem is that the viral load is dropping but not at a fast rate as I am supposed to be undetectable because I have been on ARV treatment for 2 years now and have only missed my medication once. I took another viral load test recently and the result should be out by my next doctors appointment on the 25th of this month. I just want to know what’s your expert opinion on this and what I can do. Cause one of the doctors think I’m failing the medication while the other suggests that since its dropping I should stick to it. Because another reason is that since I’m In Nigeria there isn’t much options for me

  5. Lisa Thorley

    Hi Victor,

    When you say timings what do you mean? Are you skipping meds? If you are this could be the reason why your viral load is still detectable. However, your viral load could be like this if the meds that you’re taking aren’t the right meds for you. This is something that you’ll need to talk to your doctor about as you may need to change.

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