HIV after starting ART in detail

johnwalter3 detail 3ART begins to work within hours. This is much faster than most people realise. Viral load drops dramatically and quickly in three phases.

First phase – 1 to 2 days: During the first phase, ART blocks replication in short-lived CD4 cells that are actively infected. Because these cells only live for 1 to 2 days, viral load drops by 90% within a few days.

Second phase – 2 to 3 weeks: Over the next couple of weeks, viral load continues to drop, though slightly less steeply. After a few weeks viral load has usually dropped by 99% or more.

Third phase – up to 12 weeks: If viral load is not undetectable after a month, it will continue to fall over the following few months, in the third phase. Most people reach undetectable within three months.

  • How quickly viral load drops will depend on the choice of ART.
  • How quickly viral load becomes undetectable will depend on how high it was before starting ART.
  • Good adherence is essential. Meds can only work if they are taken as prescribed.

The main aim of ART is to get viral load to below 50 copies/mL. This is called undetectable.

Once viral load gets this low, it can stay undetectable for years. As long as someone is taking their meds, the chance for the virus to develop drug resistance is very low.

  • Although viral load tests do not measure below the 50 copy cut-off, viral load can go much lower. Many people get viral load to less than 5 copies/mL and for some this is not detectable on tests measuring down to 1 copy/mL.
  • Compared to the 10 million copies/mL in early infection, it is easy to see why ART stops HIV transmission.
  • Becoming non-infectious on ART is another reason that many people start ART. The PARTNER study showed the dramatic impact of having an undetectable viral load. There were no linked HIV transmissions after couples had sex without condoms more than 100,000 times.

When to start ART

  • ART is now routine recommended for everyone who is HIV positive.
  • For most of the last 30 years, the decision to start ART depended on the CD4 count. ART was generally delayed until the CD4 count reached a certain level. This is because HIV-related complications were rare at high CD4 counts.
  • Treatment guidelines steadily increased the CD4 threshold for starting ART from 200 to 350, then to 500 and in 2015, ART was recommened for everyone.
  • The decision to treat even at high CD4 counts was due to the START study.

Early treatment in the UK

  • UK treatment guidelines recommend treatment at any CD4 count. This is based on the latest research, including the START study.
  • These UK guidelines are now similar to guidelines in other countries including the US, France and South Africa. World Health Organization (WHO) guidelines for low- and middle-income countries also recommend treatment for everyone.
  • If your doctor says that your CD4 count is too high to need treatment, and you want to start ART, say that you want to reduce the risk to your partners.
  • Many clinics offer very early ART as soon as the HIV test is confirmed. Starting ART on the same day or week you are diagnosed is a choice that can make it easier to come to terms with being HIV positive.

Same-day ART

  • Several studies have reported very positive results from offering ART when someone is diagnosed. This can be on the same day or in the same week.
  • HIV is already being treated while coming to terms with being HIV positive.
  • These studies had very high of uptake when people are given this choice. Rather than taking weeks or months of referrals and seeing specialists, ART is working immediately.
  • Viral load became undetectable more quickly in these studies.

Long-term ART: summary

  • ART has dramatically changed the outcome for people living with HIV.
  • More than 20 years of experiences shows ART is effective and with low risk.
  • Over this period, drugs have become better and research continues to make better ART. Even if no new drugs are developed, most of us will lead long and active lives. 
  • But scientists are pushing further – not just for better ART but for a cure. See HIV reservoir and cure research.
  • Longer life expectancy means that complications relating to HIV and ageing are now an important focus for research.


Last updated: 27 May 2019.