Viral 'blips'

Some people experience transient viral increases that are called ‘blips’. Viral load returns quickly to an undetectable level without any change in therapy. Various studies have found that 20 to 60% of patients with viral suppression experience viral load blips (depending on the regimen used and the frequency of viral load testing), and perhaps one-third of these experience repeated blips. Most blips are small, with viral load rising to somewhere between 50 and 1000 copies/ml.

Blips may have various causes, including variability in the testing process, temporary changes in drug concentration, or transient bursts of immune activation, for example due to receiving a vaccine or having an infection such as the flu. One study measured viral load in blood samples from ten patients every three days for four months in two separate laboratories. Nine patients had one or more viral load blips, but only one of the 18 total blips was detected by both laboratories at the same time.1

While a decrease in adherence may cause viral load to rise, most studies have shown that people who experience blips do not have worse adherence than those with consistently undetectable viral load, nor is adherence necessarily lower prior to a blip.2 Further, drug levels before, during, and after viral load blips are often greater than the minimum recommended drug concentrations.3,1

Most clinicians believe that an isolated viral load blip is nothing to worry about. However, multiple blips, or those that start occurring with increasing frequency, may be an early sign of impending treatment failure.

Blips are also not necessarily associated with emergence of drug resistance.4 However, some research suggests that transient viral load increases may be a sign of sporadic immune system activation and might help replenish latent viral reservoirs.5

The relationship between viral load blips and immune recovery is unclear.3 6 Even with the best available therapy and optimal adherence, viral blips can occur. For this reason, guidelines advise that viral load should be checked at least twice to see if the increase is an ongoing trend before deciding whether to change treatment.  


  1. Nettles RE et al. Intermittent HIV-1 viremia (blips) and drug resistance in patients receiving HAART. JAMA 293: 817-829, 2005
  2. Miller LG et al. Episodes of transient HIV viraemia (blips) are not associated with drops in medication adherence. Antivir Ther 8: S396, 2003
  3. Martinez V et al. HIV-1 intermittent viraemia in patients treated by non-nucleoside reverse transcriptase inhibitor-based regimen. AIDS 19: 1065-1069, 2005
  4. Lee PK et al. HIV-1 viral load blips are of limited clinical significance. J Antimicrob Chemother 57: 803-805, 2006
  5. Jones LE and Perelson AS Transient viremia, plasma viral load, and reservoir replenishment in HIV-infected patients on antiretroviral therapy. J Acquir Immune Defic Syndr 45: 483-493, 2007
  6. Hunt PW et al. Continued CD4 cell count increases in HIV-infected adults experiencing 4 years of viral suppression on antiretroviral therapy. AIDS 17: 1907-1915, 2003
Community Consensus Statement on Access to HIV Treatment and its Use for Prevention

Together, we can make it happen

We can end HIV soon if people have equal access to HIV drugs as treatment and as PrEP, and have free choice over whether to take them.

Launched today, the Community Consensus Statement is a basic set of principles aimed at making sure that happens.

The Community Consensus Statement is a joint initiative of AVAC, EATG, MSMGF, GNP+, HIV i-Base, the International HIV/AIDS Alliance, ITPC and NAM/aidsmap

This content was checked for accuracy at the time it was written. It may have been superseded by more recent developments. NAM recommends checking whether this is the most current information when making decisions that may affect your health.

NAM’s information is intended to support, rather than replace, consultation with a healthcare professional. Talk to your doctor or another member of your healthcare team for advice tailored to your situation.