Infectious Diseases
Sepsis, common and imported infections, and antimicrobial choice.
- Sepsis Life-threatening organ dysfunction from a dysregulated host response to infection. NEWS2 and NICE risk stratification, the Sepsis Six within the hour, and escalating septic shock.
- Pyrexia of Unknown Origin Fever persisting beyond 3 weeks with no diagnosis despite initial work-up. The four causal categories, a staged investigation strategy through to PET-CT, and why empirical treatment before a diagnosis usually backfires.
- Cellulitis and Skin Abscess Spreading dermal infection from Strep pyogenes or Staph aureus. The Eron classification for severity, antibiotic choice, and why an abscess needs drainage rather than antibiotics alone.
- Necrotising Fasciitis Rapidly progressive infection of fascia and subcutaneous tissue. Why pain out of proportion is the key clue, why LRINEC cannot rule it out, and why debridement cannot wait for imaging.
- Toxic Shock Syndrome Superantigen-mediated shock from Staph aureus or Group A Strep. The diagnostic criteria, why source control cannot wait, and why clindamycin is added to switch off toxin production.
- Osteomyelitis and Septic Arthritis in Practice Bone and joint infection from an infectious disease angle: the organism to suspect in each context, why aspiration comes before antibiotics, and how the OVIVA trial changed IV-to-oral switching.
- Infective Diarrhoea An organism-led companion to acute gastroenteritis: bacterial and parasitic causes by exposure, travellers' diarrhoea, when antibiotics actually help, and the public health duties that follow.
- Tuberculosis From primary infection and latency to reactivation and extrapulmonary disease. Diagnosis with sputum, culture and NAAT, the RIPE regimen and its side effects, and the public health duties that follow.
- HIV Progressive CD4 depletion and its predictable ladder of opportunistic disease. Recognising seroconversion and indicator conditions, testing strategy, universal test-and-treat, and IRIS.
- Infectious Mononucleosis Glandular fever from primary EBV infection. The classic triad, why amoxicillin provokes a rash, Monospot and EBV serology, and why splenic rupture drives the advice against contact sport.
- Influenza Abrupt-onset fever and myalgia from influenza A or B. Antigenic drift versus shift, at-risk groups for vaccination and antivirals, and why a biphasic illness means secondary bacterial pneumonia.
- Mumps Paramyxovirus infection causing painful parotid swelling. Orchitis, viral meningitis and sensorineural hearing loss as key complications, and why UK outbreaks recur in under-vaccinated cohorts.
- COVID-19 SARS-CoV-2 infection from mild illness to critical hypoxaemic respiratory failure. Silent hypoxia, the RECOVERY trial evidence for dexamethasone, and complications including VTE, PIMS-TS and long COVID.
- Malaria Plasmodium infection and the most dangerous cause of fever in a returning traveller. Recognising severe falciparum malaria, repeat blood films, IV artesunate, and why primaquine needs a G6PD check first.
- Typhoid and Enteric Fever Systemic Salmonella Typhi/Paratyphi infection from contaminated food or water. The stepwise fever, relative bradycardia, blood culture timing, and why fluoroquinolone resistance changed first-line treatment.
- Zoonotic Infections and Lyme Disease UK tick-borne Lyme disease and the other zoonoses unlocked by exposure history - leptospirosis, brucellosis, Q fever, psittacosis and rabies. Erythema migrans, serology pitfalls, and treatment.
- Toxoplasmosis Toxoplasma gondii infection, trivial in healthy adults but dangerous in pregnancy and immunosuppression. Congenital toxoplasmosis, cerebral toxoplasmosis in HIV, and pyrimethamine-sulfadiazine with folinic acid.
- Tetanus Clostridium tetani toxin blocks inhibitory neurotransmission, causing trismus, risus sardonicus and spasm with preserved consciousness. Wound risk assessment, tetanus immunoglobulin, and why infection doesn't confer immunity.
- Varicella Zoster Virus Primary infection causes chickenpox, reactivation causes shingles. Pregnancy and neonatal risk, ophthalmic zoster, Ramsay Hunt syndrome, and when aciclovir actually changes the outcome.
- Herpes Simplex Virus HSV-1 and HSV-2 oral and genital disease with lifelong latency. Eczema herpeticum and HSV encephalitis as emergencies, neonatal transmission risk, and empirical aciclovir on suspicion.
- Candidiasis Candida as commensal turned opportunist, from oral thrush to invasive candidaemia. Species-directed antifungal choice, source control for line infections, and the emerging threat of Candida auris.
- Hospital Acquired Infection CAUTI, CLABSI, VAP and resistant organisms. The prevention bundles that matter most - device stewardship above all - and the UK's mandatory surveillance duties.
- Surgical Site Infection Superficial, deep and organ/space infection classified by CDC criteria. Surgical wound classes, the antibiotic prophylaxis window, and the intraoperative bundle that actually reduces risk.
- Antimicrobial Stewardship Preserving the antibiotics we have. Start Smart Then Focus, the WHO AWaRe classification, IV-to-oral switch criteria, and why shorter courses are usually the right answer.
- Immunodeficiency Primary and secondary immunodeficiency classified by which immune component fails. The SPUR criteria for suspicion, why the infection pattern points to the defect, and SCID as a paediatric emergency.
- Allergic Disorders and Food Allergy IgE-mediated hypersensitivity from allergic rhinitis to food allergy and anaphylaxis. Skin prick and specific IgE testing, why IgG food testing isn't validated, and the ABCDE approach to anaphylaxis with adrenaline.