Type of Fever in Acute Rheumatic Fever
The fever in acute rheumatic fever is typically high-grade (≥38.5°C or 101.3°F) in low-risk populations, though moderate- and high-risk populations may present with lower-grade fevers (≥38°C or 100.4°F). 1
Fever Characteristics by Population Risk
The fever pattern in ARF varies based on the epidemiological risk profile of the population:
Low-Risk Populations
- Fever threshold: ≥38.5°C (101.3°F) as a minor criterion in the revised Jones Criteria 1
- This higher threshold reflects the traditional understanding that ARF presents with high-grade fever in developed nations 1
Moderate- and High-Risk Populations
- Fever threshold: ≥38°C (100.4°F) as a minor criterion 1
- This lower threshold was established after recognition that high-risk populations (such as indigenous Australians) may present with lower-grade fevers than traditionally expected 1
- The 2015 American Heart Association revision specifically acknowledged this variability to increase diagnostic sensitivity in populations where ARF remains endemic 1
Clinical Context and Timing
The fever in ARF has specific temporal and clinical characteristics:
- Fever develops 2-3 weeks after group A streptococcal pharyngitis, typically appearing 14-21 days post-infection 1, 2, 3
- The fever is part of the systemic inflammatory response and accompanies other manifestations like migratory polyarthritis 2, 4
- Fever is classified as a minor criterion in the Jones Criteria, not a major manifestation 1
Associated Laboratory Findings
When fever is present, it typically occurs alongside marked inflammatory markers:
- Erythrocyte sedimentation rate (ESR) ≥60 mm/hr in low-risk populations or ≥30 mm/hr in moderate-/high-risk populations 1
- C-reactive protein (CRP) ≥3.0 mg/dL (above upper limit of normal) 1
- In adults with ARF, ESR values >100 mm/hr (Westergren) are characteristic 4
Important Clinical Pitfalls
Do not dismiss a patient with lower-grade fever in high-risk populations, as this may represent genuine ARF rather than another condition 1. The variability in fever patterns was specifically incorporated into the 2015 revised Jones Criteria after recognition that strict adherence to high-grade fever thresholds was causing missed diagnoses in endemic areas 1.
The fever in ARF is typically described as part of a severe, febrile illness that responds to anti-inflammatory therapy, particularly high-dose aspirin, which provides dramatic symptomatic relief within 24-48 hours 2, 4.