Viral Resistance

Viral Resistance 

(See Also: Viral Load Testing and Related Issues

General Information

Understanding drug resistance.  Fact sheet from also available in Spanish

HIV resistance testing.  Fact sheet from AIDS InfoNet.  Also available in Spanish and Russian.

HIV Drug Resistance.  Detailed booklet from (PDF file).

Human Immunodeficiency Virus (HIV) laboratory tests. Fact sheet from  See descriptions of genotypic and phenotypic resistance testing.

HIV genotypic resistance testing.  Fact sheet from

HIV/AIDS drug resistance.  Web page on site with links to a question-and-answer forum, many articles, and other resources about resistance and resistance tests. 

Selected Recent Articles

Transmitted HIV Drug Resistance on the Rise in U.S.  Article dated March 21, 2012 from

Can speeding up nevirapine clearance reduce the risk of resistance after PMTCT use? Article dated January 20, 2012 from

Math Model Suggests PrEP plus ART Would Lower HIV Drug Resistance. Article dated December 14, 2011 from

Drug combinations pairing AZT and efavirenz have highest resistance risk. Article dated November 8, 2011 from

New Integrase Inhibitor BI 224436 Active against Raltegravir-Resistant HIV. Article dated October 7, 2011 from

Declining Prevalence of HIV Triple-class and Protease Inhibitor Resistance. Article dated October 7, 2011 from

Global survey shows high frequency of resistance after first-line ART failure in children. Article dated October 6, 2011 from

Some of the Most Important Lab Tests and What They Mean. Article dated September/October 2011 from Positively Aware.

Big falls in prevalence of protease inhibitor and triple-class resistance. Article dated September 19, 2011 from

Brief incarceration increases risk of rebound in viral load for patients taking HIV therapy. Article dated September 15, 2011 from

Older anti-epileptic drugs associated with failure of HIV treatment. Article dated September 2, 2011 from

Low but detectable viral load during HIV treatment involves a risk of resistance. Article dated August 2, 2011 from

Undetectable: By Whose Standard? Article dated July/August 2011 from Positively Aware.

Confirmatory viral load reduces HIV treatment switches fourfold in 6-country African study. Article dated July 6, 2011 from

Study Sheds Light on Residual Viral LoadArticle dated July 5, 2011 from

HIV Coreceptor Tropism Affects Treatment OutcomesArticle dated June 28, 2011 from

Elevated CD8 Cell Count Predicts HIV Treatment FailureArticle dated June 21, 2011 from

Low-Level NNRTI Resistance Linked to Treatment FailureArticle dated May 3, 2011 from

One in eight European children with HIV experienced failure of three drug classes within five years.  Article dated April 26, 2011 from

Study examines transmitted HIV drug resistance in Asia.  Article dated April 25, 2011 from

Raltegravir Resistance Can Emerge with Low Viral Load.  Article dated April 8, 2011 from

More than twice the risk of failure for patients starting on abacavir with low CD4s or high viral loads, compared with tenofovir.  Article dated April 7, 2011 from

Tests needed for low levels of NNRTI resistance in patients new to treatment.  Article dated April 5, 2011 from

Could Switching HIV Therapy Early Avoid Treatment Failure?  Article dated April 4, 2011 from

Breastfeeding infants with HIV may develop drug resistance from ARVs in breast milk.  Article dated March 31, 2011 from

Study shows importance of resistance testing before start of HIV treatment. Article dated March 15, 2011 from

Experimental Integrase Inhibitor Dolutegravir Looks Promising for People with Resistant HIV. Article dated March 15, 2011 from

Is HIV drug resistance spreading? Early warning signals say 'yes.' Article dated March 3, 2011 from

New data from PrEP study shed light on adherence, bone mineral loss and resistance. Article dated March 2, 2011 from

CROI 2011: Risk of Virologic Failure 40 Percent Higher Among Blacks vs. Whites. Article dated March 1, 2011 from

Virologic Failure on HIV Treatment 40% More Likely Among African Americans Than Whites, Study Finds. Article dated March 1, 2011 from The Body Pro website.

Truvada PrEP remains effective against HIV with 3TC/FTC resistance in animal study. Article dated February 28, 2011 from

Little evidence of transmission of virus that's resistant to newer anti-HIV drugs. Article dated February 9, 2011 from

Drug Resistance Shouldn't Preclude Using NRTIs in an HIV Salvage Regimen. Article dated February 1, 2011 from

Free online tool may help doctors make treatment decisions for HIV-positive patients with drug resistance. Article dated January 20, 2011 from

Women Might Have More Favorable Blood Levels of Some HIV Drugs. Article dated January 14, 2011 from

ICAAC 2010. Article from the November/December 2010 issue of Positively Aware. See section called "TMC278, Atripla, and resistance."

ICAAC 2010. Article from the November/December 2010 issue of Positively Aware. See section called "Prezista drug resistance."

Protease inhibitor monotherapy in African setting results in viral load, but not CD4, failure in the short term.  Article dated November 10, 2010 from

Persistent low-level viral load is associated with failure, but risk is small.  Article dated November 10, 2010 from

Sensitive test finds high rate of transmitted drug-resistant HIV in UK.  Article dated October 26, 2010 from

FTC therapy reduces risk of important resistance mutation. Article dated September 23, 2010 from

Protease inhibitor to raltegravir switch maintains viral suppression, but NRTI resistance lowers efficacy. Article dated July 22, 2010 from

IAC 2010: Reyataz/Isentress Combo Spares Norvir and Nukes, But Is Integrase Resistance a Concern? Article dated July 22, 2010 from

NRTI Resistance May Blunt PI-to-Isentress Switch Effectiveness.  Article dated June 14, 2010 from

Treatment and PrEP could be on a ‘collision course’, warns resistance expert.  Article dated June 1, 2010 from

If suppressed for 12 months, low risk of viral load rebound above 1000 copies. Article dated March 31, 2010 from

Drug Resistance Testing Is Effective Even With Low Virus Levels.  Article dated March 30, 2010 from

Twice-Daily ARV Treatment Better than Once-Daily for Some. Article dated March 16, 2010 from

Replication Capacity: An Additional Measure of HIV Disease Progression? Article dated March 11, 2010 from

One in Six New HIV Cases Involves Drug-Resistant Virus. Article dated March 1, 2010 from

Even very low levels of pre-existing resistance increase risk of efavirenz failure. Article dated February 10, 2010 from

Higher viral load during early pregnancy, poor adherence, associated with increased risk of HIV infection for infants. Article dated February 9, 2010 from

Less resistance with FTC than 3TC when combined with tenofovir. Article dated February 8, 2010 from

New Wave of Transmitted Drug Resistance Predicted for San Francisco. Article dated January 15, 2010 from

New resistance becoming rarer as more patients achieve undetectable HIV viral load. Article dated January 5, 2010 from 

With Poor Adherence, PIs Might Have an Advantage Over NNRTIs. Article dated December 29, 2009 from 

Transmission of Drug-Resistant HIV Drops 12-Fold in Vancouver. Article dated December 11, 2009 from

Transmitted drug-resistant HIV stabilising in Europe.  Article dated October 21, 2009 from

Triple-drug treatment during pregnancy reduces risk of nevirapine resistance.  Article dated August 13, 2009 from

Transmission of resistant HIV common in clusters of newly infected individuals.  Article dated June 10, 2009 from

Starting treatment at lower CD4 cell counts increases risk of HIV drug resistance.  Article dated June 2, 2009 from

When to start treatment: leave it no later than 350, major studies agree.  Article dated April 9, 2009 from

Treatment Adherence: Still Important.  Article dated March 24, 2009 from

Rate of transmitted drug-resistant HIV stable in France.  Article dated March 18, 2009 from

Swiss study finds moderate drug resistance; highlights difficulty of interpreting trends in changing treatment populations.  Article dated March 16, 2009 from

Drug resistance tests recommended for patients with suspected TB IRIS.  Article dated March 10, 2009 from

High failure rate for people with low CD4 nadirs in Kaletra monotherapy study.  Article dated February 16, 2009 from

Maternal resistance to nevirapine following single dose reduced by AZT/ddI or one month's ART.  Article dated February 11, 2009 from

One-a-day regimens mean better adherence for patients starting HIV treatment.  Article dated January 29, 2009 from

Treatment Adherence: Better Is Best.  Article dated December 16, 2008 from

Adherence of 80-95% not good enough for long-term treatment success in British Columbia HIV patients.  Article dated December 12, 2008 from

Raltegravir may have role in PEP if exposure involves drug-resistant HIV.  Article dated November 20, 2008 from

Non-nucleoside resistance is efficiently transmitted within infection ‘clusters.’  Article dated November 13, 2008 from

South African resistance survey confirms that clade C is more likely to develop multi-drug resistance mutation.  Article dated November 11, 2008 from

Modern HIV treatment can work well with adherence below 95%.  Article dated November 7, 2008 from

Changing the HIV Treatment Paradigm.  Article dated November 4, 2008 from

Major Updates to DHHS HIV Treatment Guidelines.  Article dated November 3, 2008 from

Higher levels of drug resistance seen after first-line NNRTI failure than boosted PI failure: meta-analysis. Article dated October 3, 2008 from

Cluster of multi-drug resistant HIV transmissions in Seattle. Article dated September 30, 2008 from 

Future Options for the Treatment Experienced.  Article dated September 24, 2008 from

Low level of drug-resistant strains common in untreated patients, but may not affect treatment. Article dated July 22, 2008 from

Guidelines reiterate resistance testing for all new HIV cases.  Article dated July 3, 2008 from 

Getting the Most from Available Antiretroviral Therapies.  Article from the Summer 2008 issue of BETA.

Boosted protease inhibitors have 60% lower risk of resistance compared with other classes.  Article dated June 18, 2008 from the

Most viral load blips are short lasting and of no significance.  Article dated May 19, 2008 from 

Improving the Predictive Ability of a Resistance Test.  Articled dated April 30, 2008 from

Current tests may miss a third of HIV resistance in treatment-naive.  Article dated April 29, 2008 from 

Most U.K. Patients Start Treatment Without HIV Resistance Info.  Article dated April 10, 2008 from

Combined Resistance Analysis Better Predicts Treatment Failures.  Article dated April 7, 2008 from

Drug Use Linked to Infection With Resistant Virus.  Article dated February 21, 2008 from


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