Patterns of Fever

Intermittent fever involves periodic fluctuations between fever and normal or subnormal temperature, occurring every few hours to three days. The temperature is typically higher in the evening than morning. This pattern differs from remittent fever, which maintains elevated temperatures without reaching normal levels, and constant fever, which remains continuously high with minimal fluctuation.

Relapsing fever is characterized by recurrent episodes where body temperature normalizes for at least one day, then rises again. This cyclical pattern distinguishes it from continuous fever. Tick-borne diseases such as Lyme disease commonly cause relapsing fever, making it clinically significant for diagnosis and patient monitoring.

During crisis, body temperature rapidly drops after prolonged high temperatures. In true crisis, temperature drops abruptly within hours and the patient's condition improves significantly. In false crisis, temperature drops but the patient's overall condition does not improve, potentially signaling disease progression rather than recovery.

Lysis fever involves temperature fluctuating in a zig-zag pattern for two to seven days before returning to normal as other symptoms gradually fade. Unlike crisis fever's rapid drop, lysis represents a gradual decline. Dengue fever characteristically exhibits lysis, where temperature drops progressively over several days.

Inverse fever occurs when maximum body temperature peaks in the morning and decreases by evening, opposite to typical fever patterns. This unusual presentation can occur in certain malaria cases due to the parasite's reproductive cycle, which causes temperature spikes during nighttime stages, resulting in morning peaks.

Remittent fever is characterized by temperature fluctuations exceeding two degrees Fahrenheit between morning and evening without reaching normal levels. The elevated baseline persists throughout the fever cycle. Infections like pneumonia and endocarditis commonly cause remittent fever patterns in clinical practice.

Fever progresses through three phases: onset or invasion, during which temperature rises suddenly or gradually; steady phase, when temperature reaches maximum and remains constant at high levels; and defervescence or decline, when elevated temperature returns to normal either suddenly or gradually.