Approach

Considerations in low-resource/tropical settings

• More infectious diseases, environment (animals, vectors), host factors (immunocompromised), may present later, pre-treatment common (e.g. antibiotics), limited diagnostics (imaging/lab)

General approach

• history, examination, investigations (biological, imaging), treatment (supportive, empirical, targeted), prevention

• Why does this person, from this place, present at this time of year in this way? (Eldryd Parry)

History

• Presenting complaint (cultural differences), history of presenting complaint (host, exposures, incubation period), past medical history, systems review (skin/rash, neurological, respiratory, cardiovascular, genitourinary, gastrointestinal, musculoskeletal), drug history (pre-treatment, traditional medicine), family history (size, structure), social history (occupation, alcohol, smoking, drugs)

Examination

• Skin

• Eschar (dead tissue found in a full-thickness wound e.g. after a burn injury, gangrenous ulcer, fungal infection, necrotizing fasciitis, spotted fevers, and exposure to cutaneous anthrax) vs. "scab" (when a crust has formed by coagulation of blood or exudate - found on superficial or partial-thickness wounds. Scab is the rusty brown, dry crust that forms over any injured surface on skin, within 24 hours of injury. Scabs generally remain firmly in place until the skin underneath has been repaired and new skin cells have appeared, after which it naturally falls off) - represents the site of inoculation, where initial multiplication occurs before widespread dissemination

• Chancre (a painless ulcer, particularly one that develops on the genitals in venereal disease)

• Bubo: a swollen inflamed lymph node in the armpit or groin

Approach to the febrile patient

• Define the clinical syndrome

• Define the exposure (animals, insects, water, food, sick contacts, sex, location [maps], timing)/risk factors (host: local, traveller, immunocompromised)

• Consider the incubation period

• Manageable differential diagnosis (public health threat? Appropriate empiric treatment, targetted investigations)

Differential diagnosis

• Depends heavily on where, when, what who... think of 3 and a good chance one will be right... common things are common ('ATM' diseases...)...

• Infectious or non-infectious (cancer, lymphoma, autoimmune, rheumatological, allergy drugs)

• Pathogens: virus (HIV, dengue), bacteria (TB, typhoid), parasite (malaria), fungi (cryptococcus), neglected/rare diseases

• Fever/bacteraemia studies

• Fever identification charts (local disease prevalence, clinical features of common and important causes of acute undifferentiated febrile illness, excluders and predictors, confirming a diagnosis)

Pathogen

Major human pathogens:

• bacteria

• viruses

• fungi

• helminths

• protozoa

• arthropods

Serotype/serovar: a distinct variation within a species of bacteria or virus (classified together based on their cell surface antigens, allowing epidemiologic classification of organisms to the sub-species level)