Recurrent Infections in Adults Algorithm

Safety

Red flags — the infection that kills today

Done

Sepsis Infection with high-risk features — new confusion, systolic BP ≤90 mmHg, heart rate >130, respiratory rate ≥25, SpO₂ <92% on air, mottled or ashen skin, non-blanching rash, no urine in 18 hours → 999 (NICE NG253).

Neutropenic sepsis Unwell with fever or suspected infection within 30 days of systemic anticancer treatment (local protocols may use longer), or on drugs that cause neutropenia (e.g. carbimazole, clozapine, methotrexate, azathioprine) → same-day via the acute oncology/alert-card pathway; do not wait for an FBC. Shocked → 999.

Asplenia with fever No spleen or hyposplenism (splenectomy, sickle cell disease, coeliac disease) with fever or rigors → take the standby antibiotic now and same-day hospital assessment — overwhelming post-splenectomy infection can kill within hours.

Haematological malignancy Recurrent infection with unexplained bruising, bleeding, pallor, lymphadenopathy, splenomegaly or night sweats → very urgent FBC (within 48 hours); blood film with blasts or suspected acute leukaemia → same-day haematology (NICE NG12).

HIV-related illness Pneumocystis pneumonia (dry cough, breathlessness, desaturation on exertion), oral candida with weight loss, or seroconversion illness → same-day HIV test and specialist advice; breathless or hypoxic → 999.

Deep or spreading infection Necrotising soft tissue infection (pain out of proportion, rapid spread), orbital cellulitis, meningism, spinal abscess (back pain + fever + neurology) → 999.

Before thinking about why infections keep happening, deal with the one in front of you. People with an underlying immune defect — neutropenia, absent spleen, HIV or a haematological cancer — deteriorate faster and present less dramatically than healthy adults, so the threshold for same-day assessment is lower. The sepsis criteria are those used across the site, from NICE NG253 (2025), which replaced NG51 for people aged 16 or over. Neutropenic sepsis is treated on suspicion, without waiting for a blood count.

Diagnose

Is this really 'too many' infections? — warning signs of immunodeficiency

Done

Probably normal

Frequent coughs and colds with full recovery, especially with young children at home, smoking, or healthcare work. Adults commonly have 2–4 viral upper respiratory infections a year.

Suspect an immune defect

Two or more serious bacterial infections (pneumonia, meningitis, osteomyelitis, sepsis) · needing intravenous antibiotics or hospital admission repeatedly · four or more courses of antibiotics a year for chest or sinus infection · infections that respond poorly or relapse as soon as antibiotics stop · unusual organisms (Pneumocystis, atypical mycobacteria, Cryptococcus, invasive fungal infection) or unusual sites (deep abscesses) · persistent thrush or warts · bronchiectasis without a cause · family history of immunodeficiency · infection plus autoimmunity, granulomas or unexplained diarrhoea and weight loss.

Pattern points to the defect

Sinus and chest, encapsulated bacteria (pneumococcus, Haemophilus) → antibody deficiency (CVID, secondary hypogammaglobulinaemia from CLL, myeloma, rituximab). Skin abscesses, fungal → neutrophil problem or diabetes. Viral, fungal, opportunistic → T-cell problem (HIV, steroids, transplant drugs). Recurrent Neisseria → complement deficiency or eculizumab.

Same site again and again

Usually a local cause rather than immune failure: bronchiectasis or COPD (chest), structural or bladder problem (UTI), nasal carriage of S. aureus (boils), skin breakdown or lymphoedema (cellulitis), diabetes or antibiotics (thrush).

Most adults who feel they "catch everything" have normal immune systems and frequent viral exposure. The warning signs separate the minority who need investigation: serious bacterial infections, repeated need for intravenous treatment, poor response, unusual organisms and a family history. The type of organism hints at which arm of the immune system is failing, which in turn guides the tests. Infections in one site usually have a local anatomical cause — bronchiectasis, a bladder abnormality, staphylococcal carriage — rather than a systemic immune defect.

Diagnose

History — secondary causes first

Done

Infection diary

Number, site, severity, organism (check microbiology results), antibiotic courses, admissions, IV treatment, recovery between episodes.

Diabetes

Thirst, polyuria, weight loss — recurrent thrush, UTI, boils and cellulitis are classic presentations.

HIV risk and indicator conditions

Sexual history, injecting drug use, partner from a high-prevalence country; shingles in more than one dermatome or under 50, recurrent pneumonia, oral candida, seborrhoeic dermatitis, unexplained lymphadenopathy, weight loss or low platelets. Offer an HIV test — most recurrent infection work-ups should include one (BHIVA/BASHH/BIA 2020).

Haematological malignancy

Fatigue, night sweats, weight loss, bone pain, bruising, lymphadenopathy, splenomegaly — CLL, myeloma and lymphoma cause secondary antibody deficiency.

Medicines

Oral corticosteroids, DMARDs (methotrexate, azathioprine, mycophenolate), biologics (anti-TNF, rituximab), JAK inhibitors, chemotherapy, transplant drugs, carbimazole and clozapine (neutropenia), antiepileptics (some lower immunoglobulins), eculizumab (meningococcus), recent repeated antibiotics (thrush, C. difficile).

Spleen

Splenectomy, sickle cell disease, coeliac disease, alcohol-related liver disease — hyposplenism.

Other secondary causes

CKD and dialysis, cirrhosis, alcohol excess, malnutrition and low weight, protein-losing enteropathy or nephrotic syndrome (lose immunoglobulin), smoking, older age and frailty.

Primary immunodeficiency

Family history, consanguinity, onset in childhood, autoimmune cytopenias, granulomatous disease, chronic diarrhoea — CVID often presents aged 20–40 after years of chest infections.

Local factors

Chest: smoking, COPD, aspiration, persistent productive cough. Urine: menopause, incomplete emptying, stones, catheter, sexual activity. Skin: eczema, lymphoedema, intertrigo, close-contact sports, household clusters.

Secondary immune problems are far more common in adults than primary immunodeficiency, so the history is a structured search for them: diabetes, HIV, drugs, cancers of the blood, an absent spleen, and organ failure. HIV testing in particular is under-used; national guidelines encourage offering a test whenever there is an indicator condition or unexplained recurrent infection. Common variable immunodeficiency, the commonest symptomatic primary antibody deficiency in adults, typically has a diagnostic delay of years and leaves behind bronchiectasis, which is why the pattern of repeated chest infections deserves attention.

Diagnose

Examination and first-line tests

Done

Examine

Observations, weight and BMI, lymph nodes, spleen and liver, chest (crackles, clubbing — bronchiectasis), ENT, skin (abscesses, scars, eczema, molluscum, warts), mouth (candida, ulcers), joints, feet in diabetes.

First-line bloods

FBC with differential and blood film (neutropenia, lymphopenia, lymphocytosis, blasts), HbA1c, U&E, LFTs and albumin, CRP/ESR, serum immunoglobulins (IgG, IgA, IgM) and serum protein electrophoresis (paraprotein, low globulin), HIV test, ferritin, B12/folate if malnourished.

Add when relevant

Serum free light chains (myeloma, NICE NG12), coeliac serology, vaccine-specific antibody responses (pneumococcal, tetanus, Hib — usually requested by immunology), blood film for Howell-Jolly bodies (hyposplenism), urine ACR (nephrotic loss).

Microbiology

Sputum culture (including for mycobacteria if persistent), MSU before antibiotics for each UTI, swab of pus (request PVL testing for recurrent boils — it is not a routine test), nasal and perineal swabs for S. aureus carriage, skin/nail scrapings for fungus.

Imaging

Chest X-ray for recurrent chest infections; HRCT for suspected bronchiectasis (via respiratory). Renal tract ultrasound for recurrent UTI in men or atypical features.

Low globulin clue

Calculated globulin (total protein minus albumin) below about 18 g/L on routine LFTs is a cheap screening clue to antibody deficiency — check immunoglobulins. Raised globulin → protein electrophoresis.

A short, inexpensive panel answers most questions: the blood count and film detect neutropenia, lymphopenia and leukaemia; HbA1c finds diabetes; immunoglobulins and electrophoresis find antibody deficiency and paraproteins; and an HIV test finds the commonest acquired cellular immunodeficiency. Low globulin on a routine liver profile is an under-recognised clue to hypogammaglobulinaemia. Specialist tests of vaccine responses and lymphocyte subsets are usually best left to immunology.

Diagnose

Differential by site and by cause

Done

Recurrent chest infections

COPD, asthma, bronchiectasis (daily productive cough — HRCT), aspiration (stroke, Parkinson's, dysphagia), lung cancer (persistent or same-lobe pneumonia — chest X-ray; NICE NG12), antibody deficiency, smoking.

Recurrent UTI

Two or more in 6 months or three or more in 12 months: menopause, incomplete emptying, stones, sexual activity, catheter, diabetes; in men usually a structural or prostatic cause.

Recurrent boils/abscesses

S. aureus nasal carriage, Panton-Valentine leukocidin (PVL)-producing S. aureus (young, healthy, household or sports clusters, painful necrotic lesions), diabetes, hidradenitis suppurativa (axillae, groins — not infective), poor hygiene or obesity.

Recurrent thrush

Four or more episodes a year: diabetes, SGLT2 inhibitors, antibiotics, steroids, pregnancy, HIV; consider non-albicans species and alternative diagnoses (lichen sclerosus, dermatitis).

Recurrent cellulitis

Lymphoedema, venous disease, tinea pedis, obesity, previous episodes.

Recurrent shingles or herpes

HIV, haematological malignancy, immunosuppressive drugs.

Systemic cause — Do not miss

Diabetes · HIV · CLL, myeloma, lymphoma, myelodysplasia · drug-induced neutropenia or immunosuppression · asplenia · CVID and other primary immunodeficiency.

Uncertain

Keep an infection diary with microbiology, review in 3 months, and seek immunology advice and guidance if the pattern persists. Abnormal results: see the abnormal immunoglobulins, leucopenia and lymphopenia algorithms.

Organising the differential by site prevents over-investigating isolated recurrent cystitis and under-investigating a man with his fourth pneumonia. Recurrent same-lobe pneumonia can be a lung cancer behind a blocked bronchus. Recurrent boils in a fit young person, or several members of one household, should prompt PVL testing because these strains cause necrotising infection and spread in families. The systemic causes listed as "do not miss" are the ones that change management beyond the next antibiotic.

Refer

Referral and urgency

Done

999

Sepsis with high-risk features · necrotising infection · meningism · respiratory failure.

Same-day

Suspected neutropenic sepsis (acute oncology) · febrile asplenic patient · blood film suggesting acute leukaemia · neutrophils <0.5 ×10⁹/L in an unwell patient · new HIV with an AIDS-defining illness.

Suspected cancer pathway

Results suggesting myeloma (paraprotein, abnormal free light chains) or lymphoma/leukaemia (e.g. lymphadenopathy, splenomegaly) → haematology (NICE NG12). Same-lobe recurrent pneumonia or chest X-ray suggesting cancer → lung.

Clinical immunology

Warning signs of immunodeficiency with low immunoglobulins (especially IgG well below the reference range) or no secondary cause; suspected CVID or complement deficiency; recurrent infection despite treating secondary causes. Very low IgG with recurrent bacterial infection → urgent referral.

HIV

Reactive test → prompt specialist HIV clinic appointment (BHIVA standard: within 2 weeks of diagnosis); same-day advice if unwell.

Respiratory

Suspected bronchiectasis (persistent productive cough, recurrent chest infections) — HRCT and specialist review; persistent sputum with mycobacteria.

Other specialties

Urology for men with recurrent UTI or women with haematuria, retention or stones; dermatology for hidradenitis; microbiology/health protection for PVL clusters.

Referral follows the cause. Immunology input is needed when the warning signs are present and the immunoglobulins are low, or when no secondary cause is found; untreated antibody deficiency causes progressive lung damage, and immunoglobulin replacement is a specialist decision. Haematological malignancy is referred on the suspected cancer pathway; neutropenia with illness is a same-day emergency. A reactive HIV test needs prompt linkage to specialist care.

Treat

Management at this consultation

Done

The current infection

Treat per local guidance

Send microbiology before antibiotics when possible; use the local antimicrobial guide; in known immunodeficiency treat earlier and for longer, with specialist advice.

Asplenia or hyposplenism

Vaccines + standby antibiotic

Pneumococcal, Hib/MenC, MenACWY, MenB and annual influenza per Green Book chapter 7. Consider lifelong prophylactic antibiotics in high-risk patients and give a standby course for fever — usual adult dose amoxicillin 500 mg three times daily (clarithromycin if penicillin-allergic); check the SPC and local formulary. Alert card; travel and malaria advice.

Recurrent boils — PVL or S. aureus carriage

Drain + decolonise

Incision and drainage is the main treatment; antibiotics only with cellulitis, systemic features or high-risk sites. If PVL-positive or recurrent S. aureus: decolonisation per UKHSA/health protection advice — commonly chlorhexidine 4% body wash daily and nasal mupirocin 2% three times daily for 5 days, ideally for household contacts at the same time, plus hygiene measures (own towels, hot wash of bedding). Seek microbiology advice for clusters.

Recurrent UTI or thrush

Confirm, then prevent

Culture each episode; check HbA1c; vaginal oestrogen for postmenopausal UTI; review SGLT2 inhibitor if recurrent thrush. Prophylaxis choices are on the protocols.

Medication-related

Review immunosuppression

Check the shared-care monitoring bloods; withhold DMARDs/biologics during an acute infection per the specialist plan; ensure pneumococcal, influenza, COVID-19 and shingles vaccines (non-live where needed).

Suspected immunodeficiency

Investigate and vaccinate

First-line bloods today; pneumococcal and influenza vaccines (before immunoglobulin replacement if possible — but avoid live vaccines until immune status is known); low threshold for antibiotics with each infection.

Next steps: see Recurrent UTI · Recurrent thrush · Bronchiectasis · HIV · Haematological cancers · Type 2 diabetes

At the first consultation the GP treats the current infection, starts the tests that find the cause, and puts protection in place for the patients who are already known to be at risk. Asplenic patients need vaccination, a standby antibiotic and an alert card because post-splenectomy sepsis is rapid and largely preventable. For recurrent boils, drainage matters more than antibiotics, and decolonisation of the patient and household is reserved for PVL-positive or proven recurrent S. aureus infection following health protection advice. Live vaccines are avoided until the immune status is clear.

Lifestyle

Self-care and prevention

Done

Stop smoking The single most effective way to reduce chest infections.

Vaccination Influenza, pneumococcal, COVID-19 and shingles as eligible; extra vaccines for asplenia or immunosuppression (Green Book).

Glucose control Better HbA1c means fewer skin, urinary and fungal infections.

Skin care Treat athlete's foot and eczema; emollients; compression for lymphoedema; don't share towels or razors.

Alcohol and nutrition Cut alcohol; aim for a healthy weight and adequate protein.

Infection diary Record dates, symptoms, test results and antibiotics — it helps the specialist.

Chest clearance Daily airway clearance exercises if bronchiectasis is diagnosed.

Many recurrent infections are reduced by simple measures — stopping smoking, better glucose control, skin care and vaccination — whatever the underlying cause. An infection diary turns a vague complaint into data that supports the referral decision.

Safety

Follow-up and safety-netting

Done

Review

Results within 1–2 weeks; review again in 3 months with the infection diary if no cause is found.

Results to chase

Immunoglobulins, electrophoresis, film, HIV, HbA1c, PVL result, chest imaging.

Known immune defect

Lower threshold for early antibiotics and same-day review; ensure the patient carries an alert card if asplenic or neutropenia-prone.

Remote consultations

Telephone, video or online consultation with any 999 feature → convert to a 999 call, not a later appointment; if examination is needed to decide, see the patient the same day.

SCA safety-net wording

"If you get a high temperature with shivering, feel very unwell, become confused or breathless, or develop a rash that doesn't fade when pressed, call 999. If you have no spleen and get a fever, start your emergency antibiotics now and get seen the same day. If this infection isn't clearly better in 48 hours, contact us."

Audit checklist

Sepsis screened · infections counted with microbiology · HIV test offered · FBC, film, immunoglobulins, electrophoresis and HbA1c done · drug causes reviewed · vaccines updated · referral decision and safety-net documented.

Follow-up ensures the investigations are completed and acted on — a common failure is an HIV test or immunoglobulin result that is never chased. Patients with a known immune defect need a clear, written plan for the next fever, because delay is what turns a treatable infection into sepsis.