Tag: AFI

  • Acute Febrile Illness (AFI) Causes

    Acute Febrile Illness (AFI): Causes

    Acute Febrile Illness (AFI) is characterized by a sudden onset of fever and associated systemic symptoms lasting for a short duration, typically less than two weeks. It is a common presentation in clinical settings and can be caused by a wide range of infectious and non-infectious etiologies. Proper identification of the underlying cause is crucial for effective management and treatment. This article provides a comprehensive list of all possible causes of AFI, including rare causes.

    Causes of Acute Febrile Illness (AFI)

    Table 1: Causes of AFI (Including Rare Causes)

    TypeCauseExamples
    Infectious CausesBacterial InfectionsTyphoid Fever, Pneumonia, Meningitis, UTIs, Endocarditis, Brucellosis, Tularemia, Anthrax, Q Fever, Melioidosis, Leprosy, Lyme Disease, Rickettsial infections (Rocky Mountain Spotted Fever, Scrub Typhus)
    Viral InfectionsDengue, Influenza, COVID-19, Chikungunya, Measles, Mumps, Rabies, Hantavirus, Viral Hemorrhagic Fevers (Ebola, Marburg), West Nile Virus, Zika, Crimean-Congo Hemorrhagic Fever (CCHF), Lassa Fever, Nipah Virus
    Parasitic InfectionsMalaria, Leptospirosis, Trypanosomiasis, Toxoplasmosis, Babesiosis, Schistosomiasis, Amoebiasis, Fascioliasis, Filariasis, Echinococcosis
    Fungal InfectionsCandidiasis, Histoplasmosis, Coccidioidomycosis, Cryptococcosis, Blastomycosis, Paracoccidioidomycosis, Sporotrichosis, Aspergillosis
    Non-Infectious CausesAutoimmune DisordersSystemic Lupus Erythematosus (SLE), Rheumatic Fever, Still’s Disease, Sarcoidosis, Vasculitis, Adult-onset Still’s Disease (AOSD), Polyarteritis Nodosa
    Malignancies (Neoplastic)Lymphoma, Leukemia, Renal Cell Carcinoma, Hepatocellular Carcinoma, Multiple Myeloma, Metastatic Cancers, Paraneoplastic Syndromes
    Drug-Induced FeversAntibiotics, Anticonvulsants, Chemotherapy, NSAIDs, Antiarrhythmics, Vaccines, Biologics, Illicit Drug Reactions
    Environmental CausesHeat StrokeHeat Stroke, Hyperthermia due to extreme environments, Neuroleptic Malignant Syndrome (NMS)
    Hyperthermia from ToxinsCocaine, Amphetamines, Anticholinergics, Salicylate Toxicity, Serotonin Syndrome
    Unknown CausesFever of Unknown Origin (FUO)Idiopathic Fevers, Familial Mediterranean Fever (FMF), Adult-onset Immunodeficiency Syndrome (AOIS), Periodic Fever Syndromes

    Pathophysiology

    1. Infectious Causes (Most Common)

    • Bacterial Infections:
      • Pathophysiology: Activation of immune response via endotoxins or exotoxins leading to cytokine release (IL-1, TNF-α).
      • Examples:
        • Typhoid Fever (Salmonella typhi)
        • Pneumonia (Streptococcus pneumoniae, Haemophilus influenzae)
        • Meningitis (Neisseria meningitidis, Streptococcus pneumoniae)
        • Urinary Tract Infections (E. coli)
    • Viral Infections:
      • Pathophysiology: Viral replication causing cell lysis, immune activation, and cytokine storm.
      • Examples:
        • Dengue Fever
        • Influenza
        • COVID-19 (SARS-CoV-2)
        • Chikungunya
        • Measles, Mumps
    • Parasitic Infections:
      • Pathophysiology: Immune response to parasitic antigens; inflammation and tissue damage.
      • Examples:
        • Malaria (Plasmodium spp.)
        • Leptospirosis (Leptospira spp.)
        • Trypanosomiasis (African Sleeping Sickness)
    • Fungal Infections:
      • Pathophysiology: Invasive fungal infections trigger inflammatory responses, especially in immunocompromised individuals.
      • Examples:
        • Candidiasis
        • Histoplasmosis

    2. Non-Infectious Causes

    • Autoimmune Disorders:
      • Pathophysiology: Autoimmune activation causing systemic inflammation and fever.
      • Examples:
        • Systemic Lupus Erythematosus (SLE)
        • Rheumatic Fever
        • Still’s Disease
    • Malignancies (Neoplastic):
      • Pathophysiology: Release of pyrogens from cancer cells or tumor necrosis.
      • Examples:
        • Lymphoma
        • Leukemia
        • Renal Cell Carcinoma (Paraneoplastic syndromes)
    • Drug-Induced Fevers:
      • Pathophysiology: Hypersensitivity reactions or alteration in thermoregulation.
      • Examples:
        • Antibiotics (e.g., Beta-lactams)
        • Anticonvulsants (e.g., Phenytoin)
        • Chemotherapy agents

    3. Environmental Causes

    • Heat Stroke:
      • Pathophysiology: Failure of thermoregulation leading to hyperthermia and systemic inflammatory response.
    • Hyperthermia from Toxins:
      • Pathophysiology: Direct effect on hypothalamic regulation or increased metabolic rate.
      • Examples:
        • Cocaine, Amphetamines
        • Anticholinergic overdose

    4. Unknown/Idiopathic Causes

    • Fever of Unknown Origin (FUO):
      • Pathophysiology: Persistent fever (>3 weeks) without clear etiology despite thorough investigation.

    References

    1. Mandell, Douglas, and Bennett’s Principles and Practice of Infectious Diseases, 9th Edition.
    2. Harrison’s Principles of Internal Medicine, 21st Edition.
    3. Kumar & Clark’s Clinical Medicine, 10th Edition.
    4. Fauci AS, et al. (2020). Harrison’s Principles of Internal Medicine. McGraw-Hill.
    5. Shapiro DS, et al. (2019). Infectious Disease: A Clinical Short Course. McGraw-Hill.
    6. Longo DL, et al. (2019). Fever of Unknown Origin. New England Journal of Medicine.