Reasoning GP · Algorithm · 1-page summary
Recurrent infections in adults
For: adults in primary care with repeated or unusual infections. Not for: children (paediatric pathways); the acute management of a single infection (see the infection protocols).
Core rule: treat today's infection safely, then look for the secondary cause — diabetes, HIV, blood cancer, drugs, absent spleen — before blaming bad luck; FBC, film, immunoglobulins, electrophoresis, HbA1c and HIV test.
0Stop — call 999 now
- Sepsis high-risk features — new confusion, systolic ≤90, HR >130, RR ≥25, SpO₂ <92%, mottled skin, non-blanching rash → 999
- Necrotising infection (pain out of proportion), meningism, spinal abscess (back pain + fever + neurology) → 999
1Triage — is it "too many"?
| Pattern | Meaning → action |
|---|---|
| Colds, full recovery | Usually normal → reassure, diary |
| Same site | Local cause (bronchiectasis, bladder, carriage) |
| ≥2 serious bacterial | Suspect immune defect → bloods |
| IV antibiotics, poor response | Suspect immune defect → bloods |
| Unusual organism | T-cell defect, HIV → test |
2Screen — serious causes
- Neutropenic sepsis — unwell within 30 days of anticancer treatment or on neutropenia-causing drugs → Immediate acute oncology hotline / 999; do not wait for FBC.
- No spleen + fever → standby antibiotic now, Same-day hospital.
- Bruising, lymphadenopathy, splenomegaly, night sweats → very urgent FBC (48 hours); film with blasts → Same-day haematology.
- Paraprotein / abnormal free light chains → Suspected cancer haematology.
- Pneumocystis, oral candida + weight loss → Same-day HIV test and advice.
3Assess
☐ Infection count, sites, organisms, admissions ☐ Drugs: steroids, DMARDs, biologics, chemo ☐ FBC + film, HbA1c, U&E, LFTs/albumin, CRP ☐ IgG/IgA/IgM + electrophoresis ☐ HIV test ☐ Cultures before antibiotics
Boils: ask the lab for PVL testing on pus. Chest: X-ray; HRCT via respiratory.
4Classify — only if blocks 0–2 are negative
- Chest — COPD, bronchiectasis, aspiration, same-lobe pneumonia (cancer), antibody deficiency.
- UTI — menopause, emptying, stones, diabetes; men → structural.
- Boils — S. aureus carriage, PVL (clusters, young, necrotic), diabetes, hidradenitis.
- Thrush — diabetes, SGLT2i, antibiotics, steroids, HIV.
- Systemic — diabetes, HIV, CLL/myeloma/lymphoma, drugs, asplenia, CVID.
- Uncertain — infection diary with microbiology, review in 3 months, immunology advice.
5Treat today — doses: NICE/SPC, BNF, local formulary
- Current infection: culture first; local antimicrobial guide.
- Asplenia: Green Book vaccines; standby amoxicillin 500 mg three times daily (clarithromycin if allergic); alert card.
- Boils: drain; PVL or recurrent S. aureus → decolonise per health protection advice (chlorhexidine 4% wash + nasal mupirocin 2%, 5 days), household together.
- Suspected immunodeficiency: inactivated vaccines; avoid live vaccines until immune status known.
6Refer routinely and review
- Immunology: warning signs + low immunoglobulins, or no secondary cause.
- HIV clinic: reactive test — within 2 weeks (BHIVA).
- Respiratory: suspected bronchiectasis. Urology: men with recurrent UTI.
7Never reassure by
- "Just unlucky" without counting serious infections.
- A normal white count — check the film and immunoglobulins.
- Not offering an HIV test.
- A normal CRP in an immunosuppressed patient.
- Repeated antibiotics for boils without drainage or PVL testing.
- Treating recurrent chest infections without a chest X-ray.
8Safety-net — say it, then document it
999 “High temperature with shivering, feeling very unwell, confused or breathless, or a rash that doesn't fade when pressed — call 999.” Same-day “No spleen and a fever — start your emergency antibiotics and get seen the same day.”
Not clearly better in 48 hours → contact us. Remote consultation with any 999 feature → convert to a 999 call.
✓Safe to leave primary care only if — all five, documented
No sepsis or block 2 feature
Infections counted with microbiology
FBC/film, Ig, electrophoresis, HbA1c done
HIV test offered; drugs reviewed
Vaccines, referral and safety-net recorded
Summary of the full Reasoning GP recurrent infections algorithm, which holds the history, differential, investigations, lifestyle and evidence. Sources: NICE NG253, CG151, NG12 (updated April 2026), BHIVA/BASHH/BIA HIV testing 2020, NG60, UKHSA Green Book ch.7, BCSH asplenia 2011, DH/HPA PVL-SA 2008, NG112, NG117. Clinical reference — follow local microbiology and immunology pathways and check doses: NICE/SPC, BNF.