The infectious diseases history.
The entire ID differential comes down to two questions: what was the patient exposed to, and what are they susceptible to. Both pillars, plus the social history that ties them together, anchored to an incubation timeline.
Reviewed June 2026 · verify against current guidelines
Two pillars
Exposure × susceptibility.
Exposures: where & what
- Travel: destinations, dates, rural vs urban, prophylaxis.
- Animals & vectors: pets, livestock, tick or mosquito bites.
- Food & water: undercooked meat, raw dairy, fresh water.
- Work & hobbies: farm, healthcare, hiking, caving, hunting.
- Blood & fluids: transfusion, needlestick, tattoos, piercings.
- Contacts: sick contacts, outbreaks, institutional settings.
Host risk: who is vulnerable
- Immune status: HIV, transplant, chemo, steroids, biologics.
- Asplenia: anatomic or functional (sickle cell); neutropenia.
- Comorbidities: diabetes, cirrhosis, renal, pregnancy.
- Devices: lines, implants, recent surgery or hospitalization.
- Drugs: antibiotics, immunosuppressants, injection use.
- Vaccines: immunization gaps; prior serious infections.
The illness & social history
Characterize the illness.
- Onset & tempo: acute, subacute, or chronic; how it is progressing.
- Fever: pattern, height, rigors, drenching night sweats.
- Constitutional: weight loss, anorexia, fatigue, malaise.
- Localizing symptoms: a full review of systems, head to toe.
- Sexual history (5 Ps): partners, practices, protection, past STIs, pregnancy plans.
- Substance use: alcohol, tobacco, and recreational or injection drugs.
- Past infections: prior cultures, latent tuberculosis, antibiotic responses.
- Living situation: housing, homelessness, incarceration, shelters, daycare.
- Family history: infections, immunodeficiency, or similar illness.
- Medications & allergies: recent antibiotics, prophylaxis, immunosuppressants.
Two questions drive the differential: what was the patient exposed to (anchored to an incubation timeline) and what are they susceptible to. Exposures plus host, every time.
HIV human immunodeficiency virusSTIs sexually transmitted infections
Sources
Verify against current guidelines and local protocol before acting.
- Standard ID history references (I MD SOAPS exposure framework; CDC 5 Ps sexual history)
Downloads
Every card behind this topic, as published — view full size or download.
