Endocarditis must be differentiated from other causes of a fever of unknown origin (FUO) such as pulmonary embolism, deep vein thrombosis, lymphoma, drug fever, cotton fever, and disseminated granulomatoses.^[1]

Endocarditis must be differentiated from other causes of a fever of unknown origin such as:^[1]

• Lymphoma
• Pulmonary embolism
• Deep vein thrombosis
• Drug fever
• Cotton fever
• Disseminated granulomatoses such as tuberculosis, histoplasmosis, coccidioidomycosis, blastomycosis, and sarcoidosis

A drug fever will resolve with discontinuation of the offending agent. There may be elevated urine eosinophils and a peripheral eosinophilia as well.

The symptoms of cotton fever resemble those of sepsis and patients may be initially misdiagnosed upon admission to a hospital. However sepsis is a serious medical condition which can lead to death, whereas cotton fever, if left alone, will usually resolve itself spontaneously within 12-24 hours. Symptoms usually appear with 10-20 minutes after injection and in addition to fever may include headaches, malaise, chills, nausea and tachycardia. The fever itself usually reaches 38.5 – 40.3°C (101 – 105°F) within the first hour.^[2]

Table 1; Differentiating psittacosis from other diseases

Key;

+, occurs in some cases

++, occurs in many cases,

+++, occurs frequently