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Viral load and CD4 count

whats happening inside me

Doctors use two key tests to assess the strength of your immune system - a CD4 cell count and a viral load test.

HIV damages your immune system even though you may look and feel well, so guidelines recommend that everyone with HIV starts treatment whatever their CD4 count.

Effective treatment also reduces the amount of virus in your blood to ‘undetectable’ levels which means you cannot pass on HIV.

What happens after infection:

When you first get HIV, your body starts to produce antibodies to fight it off.

You may feel ill for a while at this stage. This is often called seroconversion illness because it coincides with the time that blood (‘sero’) tests for HIV antibodies become (‘conversion’) positive.

As you can see on the graphic below, you will also be infectious during this period, even though you may not be aware you have HIV.

Viral load explained

The viral load test shows how much HIV is in your body by measuring how many particles of HIV are in a blood sample. The results are given as the number of ‘copies’ of HIV per millilitre of blood - for example 200 copies/ml.

Looking at the trend over a number of months may be more useful than comparing two test results.

A high viral load will usually – but not always – mean a low CD4 count.

CD4 and viral load

Your viral load test results can fluctuate a lot if you’re not taking HIV treatment – in this case a viral load above 100,000 is considered high and one below 10,000 is considered low. The aim of treatment is to reduce this to undetectable levels, which means you cannot pass HIV on.

What is an undetectable viral load?

An undetectable viral load doesn't mean there's no HIV present - HIV is still there but in levels too low for the laboratory test to pick up. Different laboratories may have different cut off points for classifying viral load as undetectable, but most clinics in the UK classify undetectable as being below 20 copies/ml.

What is the CD4 cell count?

This test gives a rough indication of the strength of your immune system. CD4 cells are important immune system cells which are used by HIV to reproduce. After HIV has reproduced the CD4 cell will die.

A normal CD4 cell count in an HIV negative man is between 400 and 1,600 per cubic millimetre of blood (but doctors normally just give a figure, eg, 500). CD4 cell counts in HIV negative women tend to be a little higher, between 500 and 1,700.

Soon after infection with HIV, your CD4 cell count drops sharply, before stabilising at around 500 to 600. Even while you’re well and have no obvious symptoms of HIV, millions of CD4 cells are infected by HIV and lost every day, and millions more are produced to replace them. General illness can also have an impact on your CD4 count, which may subsequently rise again.

Without treatment, an HIV positive person’s CD4 cell count will fall over time (see the graphic above).

Can treatment stop me being infectious?

Yes. If you’re taking HIV medication and have an undetectable viral load you cannot pass on HIV. 

It can take up to six months on treatment to become undetectable.

How do we know this?

A large study called PARTNER looked at 888 gay and straight couples (and 58,000 sex acts) where one partner was HIV positive and one was HIV negative. Results found that where the HIV positive partner was on treatment and had an undetectable viral load, there were no cases of HIV transmission whether they had anal or vaginal sex without a condom.

The PARTNER study looked at couples where the HIV positive partner had a viral load below 200. An undetectable viral load is usually classed as being below 20 copies/ml.

The Partners PrEP study looked at the risk of transmission in the time it took the HIV positive partner to achieve an undetectable viral load. In most cases (84.8%) this happened within six months and there were no infections once someone had been on treatment for six months or more.

Before deciding to stop using condoms, it’s a good idea to speak to your HIV doctor or nurse to make sure your viral load is undetectable.

It’s also important to remember that if you have sex without a condom other sexually transmitted infections (STIs) can be passed on.

Sex without a condom can also result in an unplanned pregnancy if other contraception is not being used.

When should I start treatment?

The British HIV Association (BHIVA) treatment guidelines recommend that anyone with HIV who is ready to commit to treatment should start regardless of their CD4 count. This reflects the findings of the START study.

START found that people who waited to start treatment until their CD4 count dropped to 350 (which is when people were previously advised to start) had a significantly higher chance of developing AIDS-related illnesses such as cancers.

More on HIV and treatment:

Next: The stages of HIV infection ››

‹‹ Previous: The immune system



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  • After recently being diagnosed in June 2012 my CD4 count was only 174 and Viral Load was 1.5 million. I started treatment straight away and am now 8 weeks in to anti-viral treatment and my CD4 as of last week was 473 and viral load 3323. The clinincal team and specialists have been amazing plus they were amazed with the changes in me. I had been in a relationship for nearly 4yrs and found out about my status after that relationship finished. I advise people no matter how stable your relationship is, go and get tested. At first I was ending my life when I found out but with support and things I'm healthier than I can imagine.

    Posted 13:42 Wed 10 Oct 2012
  • My CD4 was 90 when I started treatment and today my CD4 is 600.
    Within 6 months I took things serious as I was recovering and set myself to learn more of HIV and how to live with HIV.
    My GP in Goa, India was my guide to help me know more on HIV prior to me migrating to UK
    All is as of today OK with me but yes I have put on 15 lbs extra weight after starting medication since 2011.
    I do speak and advise many of HIV and how to be protected from this sickness.

    Posted 12:31 Tue 01 Jan 2013
  • when i got diagnosed in october 2012 my cd4 was 290 and my viral load was 40000 copies after a month and a week of medication i had my first blood tests on the 7th of january 2013 i was amazed that my viral load has come down to just 68 copies. they say it comes down fast initially but slows down after the first month now i am working towards getting to undetectable. i am very pleased.

    Posted 15:40 Wed 16 Jan 2013
  • I was diagnosed after Pneumonia in 2012. My CD4 count was twenty!. My viral load was 1.5 million. I am still alive !! Thanks to the team.

    Posted 01:03 Sat 16 Mar 2013
  • I was diagnosed in Feb 2012 and my CD4 count was 920 and viral load was 17,000. Since then my CD4 has gradually dropped to 620 which may be a result of the odd bout of FLu etc. Are there any of you that struggled to come to terms with diagnosis and who have worried about meeting a partner with the "burden" of HIV that could maybe post some advice here? Much appreciated ;0)

    Posted 22:47 Wed 20 Mar 2013
  • I was diagnosed in Feb 2012 and my CD4 count was 920 and viral load was 17,000. Since then my CD4 has gradually dropped to 620 which may be a result of the odd bout of FLu etc. Are there any of you that struggled to come to terms with diagnosis and who have worried about meeting a partner with the "burden" of HIV that could maybe post some advice here? Much appreciated ;0)

    Posted 22:49 Wed 20 Mar 2013
  • I was daignosed January 2012 my CD4 count was 750 now still not on medication and my CD4 count is 113, I pray it stays that was my viral load is 1162

    Posted 13:48 Sat 15 Mar 2014
  • Just to share my own numbers to help others:

    Diagnosed 3 months ago - a big shock
    VL 101k CD4 384

    Started medication straight away
    4 weeks in... VL down to 84 and I expect to be undetectable at my next blood test.

    CD4 will take longer to build back up - but psychologically it feels good to be taking positive action (no pun intended)

    Posted 16:17 Thu 18 Dec 2014
  • Hi was diagnosed in 2012 my cd4count was 850 and viral load was 1113 I have not had to take any medication my cd4 count is now 1200 and my viral load is1300 so everything is still okay I pray I stay like that for some time ., one thing I have found difficult is to meet a new man in my life I don't know how I would be able to explain my status so I have stayed away from them , I do get a bit lonely , hopefully one day I will meet one that is hiv positive and it might just work out .

    Posted 00:01 Sat 21 Feb 2015
  • I was diagnosed on 4 Feb 2015. My viral load was 9,000,000 (Yes 9 million) and my CD4 count was 290. After 6 weeks on medication my viral load is down to 5,200. An incredible drop. The drugs I take are Truvada, Ritonavir and Durunavir. I won't get my CD4 count until 2 months time on my next visit to the Doctor. I was very ill but am so much better now.

    Posted 18:01 Thu 26 Mar 2015
  • My viral load undetectable twice last year now I tested my Viral load last week it came 22 copie/ml so what's mean that ? My viral load under undetectable or no ? What is the range of undetectable viral load ? As my knowledge over 75 copie/ml viral load its call detectable m I right ?

    Posted 06:03 Mon 30 Nov 2015
  • I was diagnosed as HIV positive in May 1997. My VL was well above a million copies and CD4 was 187. I reluctantly started treatment and 19 years later I remain very well. I have never had an opportunistic infection episode and my current treatment with Atripla has served me well. My recent CD4 in March 16 was 791 and my Viral Load has been undetectable for most of the time I have been on treatment. I have just retired from full time work and I am having a good time doing simple things. I hope my comment encourages others who may be short of hope. I am 62 years old and hope to be around for many more years thanks to science, medical practice and the kindness of family and friends. Never give up and take your medicine exactly as prescribed! Marcus

    Posted 18:36 Thu 05 May 2016
  • I was diagnosed 04/2005 with CD4 60 and viral load estimated at well over 1.6 million.within 3 months my CD4 was 200 and viral load undetectable. And as of today 16/08/2016 still on same meds I started on an still undetectable

    Posted 18:38 Tue 16 Aug 2016
  • I just got my confirmed diagnosis yesterday. I am hiv positive. Just helps to say it. Still numb and disbelieving

    Posted 12:35 Sat 12 Nov 2016
  • I was diagnosed in February ('m pretty sure I contracted it in November) Got the results of my first load of blood tests today. CD4 was 935 and VL 9500. Starting medication next week and am feeling positive about the future :)

    Posted 19:34 Tue 09 May 2017
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The Information Standard: Certified member

This article was last reviewed on 25/1/2017 by Anna Peters

Date due for the next review: 25/1/2020

Content Author: Kerri Virani

Current Owner: Kerri Virani

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