Viral load “blips” and eventual rebound

Cal Cohen, M.D. for

During the past few years, it has been repeatedly shown that any regimen that gets viral loads down to below 50 copies is clearly more durable in maintaining viral suppression than those regimens that do not achieve this degree of viral suppression.

However, it has also been noted that some people who have a viral load below 50 will also, occasionally, have a viral load above this level. There have been a few groups who have helped define the impact for those whose viral loads go transiently above 50 copies, after viral suppression was achieved on a regimen. This pattern has been commonly referred to as a viral load “blip.”

For this study, a group of European researchers monitored the viral loads of about 2,500 people who were on standard triple regimens. The group monitored the outcome for those who, while on antivirals, had a viral load below 50 copies on two consecutive tests. They defined viral rebound, or failure, as a viral load over 500 copies. They examined the rates of failure in those whose viral loads went over 50 copies but were less than 500 copies Ñ this is the range defined as a “blip” in this study. Most of those who had one reading in this range had viral suppression below 50 copies on the next reading, although about 20% did rebound on a follow-up reading. They then examined the number of consecutive readings in this low range, to see if that was important in predicting who would re-suppress versus those who would rebound. In fact, the longer someone had a viral load between 50 and 500, the more likely there was eventual rebound. Those who had a sustained viral load between 51-500 were five times more likely to eventually go over 500 copies than those who stayed below 50 copies on all readings. Moreover, they noted that there was a trend showing a difference in the rates of rebound for those whose viral loads were between 50-100 copies, versus those whose “blip” was between 100-500 copies, as the group with the lower level blip were more likely to re-suppress.

These results confirm what we might have predicted from prior work done in defining the keys to successful suppression. Overall, if HIV can grow in the presence of antiviral medication, it can eventually create resistance to these medications and this leads to higher and higher viral load levels Ñ heading back toward the patient’s pre-treatment set point.

For reasons that remain unclear, there seems to be ongoing success for those people who have viral loads below 50 copies, which differs from the success rates for people with a viral load even just a small amount over 50 copies. This study suggests that both the duration and height of the “blip” are helpful in predicting how likely it is that HIV will stay suppressed despite a blip. However, it also emphasizes the point that, while one blip at a low level may have little impact, higher-level blips, or sustained low-level viral loads, may be a precursor to eventual viral escape. Re-emphasising medication adherence is certainly warranted as one first step to prevent this outcome.



Greub G, Cozzi Lepri A, Ledergerber B et al. Low-Level HIV Viral Rebound and Blips in Patients Receiving Potent Antiretroviral Therapy. 8th Conference on Retroviruses and Opportunistic Infections; February 4-8, 2001; Chicago, Illinois. Abstract 522.

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