References UK clinical guidance from the NHS, the British HIV Association (BHIVA), and the British Association for Sexual Health and HIV (BASHH). Last updated: April 2026.
Immune reconstitution inflammatory syndrome (IRIS) is a condition that can happen in the first weeks or months after starting HIV treatment, particularly in people who start ART with a very low CD4 count. It occurs when the recovering immune system mounts an inflammatory response against infections that were already present but hidden while the immune system was suppressed.
IRIS can be alarming, but it’s a sign that your immune system is waking up. With proper management, most people recover fully.
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What Causes IRIS?
When you start ART, your CD4 count rises and your immune system begins to recover. If you had an existing opportunistic infection — even one you didn’t know about — the newly active immune system can overreact to it. This excessive inflammatory response is IRIS.
Two Types of IRIS
| Type | What Happens |
|---|---|
| Paradoxical IRIS | A known infection that was being treated gets temporarily worse after starting ART |
| Unmasking IRIS | A previously hidden infection becomes apparent for the first time after starting ART |
Common Infections Involved
- Tuberculosis (the most common trigger)
- Mycobacterium avium complex (MAC)
- Cryptococcal meningitis
- Pneumocystis pneumonia (PCP)
- Cytomegalovirus (CMV)
- Kaposi’s sarcoma
- Hepatitis B or C flares
Symptoms
Symptoms depend on the underlying infection and can include:
- Fever
- Swollen lymph nodes
- Worsening respiratory symptoms
- New headache or confusion
- Skin lesions getting worse
- Abdominal pain
Symptoms typically start within 4-8 weeks of beginning ART, though they can occur later.
How Is IRIS Managed?
- Continue ART — stopping treatment is usually not recommended
- Treat the underlying infection aggressively
- Anti-inflammatory medication — corticosteroids are sometimes used for severe IRIS
- Close monitoring — regular clinic visits until symptoms resolve
Risk Factors
- Starting ART with a very low CD4 count (below 50)
- High viral load at the time of starting treatment
- Active opportunistic infection at ART initiation
- Short interval between infection treatment and ART start
This is one reason why HIV specialists sometimes delay starting ART briefly while treating an acute opportunistic infection — to reduce IRIS risk.
Read more: What is HIV? | HIV and the immune system | Lung problems and HIV
Frequently Asked Questions
Does IRIS mean my treatment isn’t working?
No — the opposite. IRIS happens because your immune system is recovering. It’s an inflammatory overreaction, not a sign of treatment failure.
Should I stop my HIV medication if I get IRIS?
Usually not. Your HIV team will manage IRIS while keeping you on ART. Stopping treatment would risk further immune decline.
How long does IRIS last?
Most cases resolve within weeks to a few months with appropriate treatment. Severe cases may take longer but full recovery is the norm.
Related reading
- A to Z of Sex: Sexual Health Terms Explained
- Alcohol and HIV: What You Need to Know
- Anxiety and HIV: Coping and Getting Support
- Are All STIs Curable?
- Blood Problems and HIV: Anaemia, Low Platelets and More
Sources
- NHS — Sexual health conditions
- BASHH — UK clinical guidelines for STI management
- British HIV Association (BHIVA) — HIV treatment guidelines
- Terrence Higgins Trust — sexual health information
- UK Health Security Agency — STI surveillance data
Steve Page is a recognised expert on Sexually Transmitted Diseases (STDs) and STD treatments, having published numerous articles in peer-reviewed journals and presented his research at conferences around the world. He has an in-depth understanding of the latest medical research on STDs, and is an advocate for the development of new treatments and protocols to improve the health of those affected. In addition to his research, he has dedicated his career to understanding the causes and symptoms of STDs, as well as how to best treat those impacted.
