Pertussis can be easy to miss when the classic whoop is absent. This concise review anchors the timeline from coryzal symptoms to paroxysmal cough, and links swab timing, macrolides, exclusion advice and vulnerable contacts to transmission control.

Adolescents and young adults with sore throat, fatigue and posterior cervical lymphadenopathy need EBV in the differential. The clinically useful details are testing timing, the amoxicillin rash clue, splenomegaly checks, alcohol advice and contact sport restriction.

Headache, fever, altered consciousness, unusual behaviour or seizures need a neurological infection pathway in view. Open this for herpes simplex virus, varicella zoster virus and cytomegalovirus encephalitis, lumbar puncture viral PCR, MRI brain, antiviral matching and longer-term cognitive or behavioural follow-up.

Fever, neck stiffness, vomiting, headache, photophobia or non-blanching rash make this the place to begin. It keeps suspected bacterial meningitis time-critical, with urgent transfer, antibiotics, lumbar puncture contraindications, paired blood glucose and CSF interpretation held together.

Fever in a child with lethargy, poor intake, reduced urine output, mottled or ashen appearance, or a non-blanching rash makes this the first listen. It ties sepsis recognition to ABCDE assessment, senior support, cultures, intravenous antibiotics and cautious fluid boluses with reassessment.

Routine immunisation is a moving schedule, so age-matching matters before reassurance or administration. The quick check is live-vaccine caution in immunocompromised children, HPV cancer prevention before exposure, BCG for increased tuberculosis risk and MenB fever advice up to 48 hours.

Recurrent meningococcal disease or unexplained lip, face, airway or abdominal swelling should prompt immune pathway thinking. Complement 5 to 9 deficiency and hereditary angioedema are different problems, but both need recognition before repeated isolated episode management.

Recurrent viral, fungal or opportunistic infection points away from simple humoral thinking. The paediatric immunodeficiency review is concise: look for congenital heart disease, cleft palate, hypocalcaemia, eczema with small platelets, ataxia, telangiectasia and live vaccine illness.

Recurrent respiratory infections with chronic diarrhoea or failure to thrive should prompt immunoglobulin thinking, not another isolated infection plan. The main distinctions are IgA deficiency, common variable immunodeficiency, X-linked agammaglobulinaemia and hyper-IgM syndrome.

A young infant with persistent diarrhoea, failure to thrive and severe infections should move severe combined immunodeficiency up the list. This is the best opener for bedside practice: ask about candidiasis, chickenpox, Pneumocystis jirovecii pneumonia and illness after live vaccination, then escalate early.