Fever in adults

Fever in adults is defined as a body temperature above 100.4°F (38°C) and is a common symptom of various underlying conditions. It is the body’s natural response to infection, inflammation, or other medical issues. Below is a comprehensive list of potential causes of fever in adults:

1. Infectious Causes

Infections are the most common cause of fever. These can be localized or systemic and include:

Viral Infections:

Common cold or influenza (flu)
COVID-19
Mononucleosis (caused by Epstein-Barr virus)
Viral gastroenteritis (stomach flu)
Hepatitis (A, B, C)
HIV/AIDS (acute retroviral syndrome)
Dengue fever, Zika virus, or other arboviruses

Bacterial Infections:

Urinary tract infections (UTIs)
Pneumonia
Strep throat or tonsillitis
Tuberculosis (TB)
Sinusitis or ear infections
Skin or soft tissue infections (cellulitis, abscesses)
Bacterial gastroenteritis (e.g., Salmonella, E. coli)
Lyme disease
Sexually transmitted infections (STIs) like gonorrhea or chlamydia
Sepsis (life-threatening systemic infection)

Fungal Infections:

Candidiasis (thrush or systemic fungal infections)
Histoplasmosis or coccidioidomycosis (in endemic areas)

Parasitic Infections:

Malaria
Toxoplasmosis
Giardiasis
Amebiasis

2. Inflammatory and Autoimmune Conditions

Fever can result from the body’s immune system attacking its own tissues or due to chronic inflammation:

Rheumatoid arthritis
Systemic lupus erythematosus (SLE)
Vasculitis
Inflammatory bowel disease (IBD: Crohn’s disease, ulcerative colitis)
Sarcoidosis

3. Medications and Vaccines

Drug-Induced Fever: Certain medications can cause fever as a side effect (e.g., antibiotics like penicillin, anticonvulsants, or antihistamines).
Vaccine Reaction: Fever is a common side effect after vaccinations (e.g., flu shot, COVID-19 vaccine).

4. Malignancies (Cancers)

Fever can be a symptom of certain cancers or their treatments:

Leukemia or lymphoma
Renal cell carcinoma
Liver cancer
Metastatic cancers

5. Blood Clots and Vascular Issues

Deep vein thrombosis (DVT)
Pulmonary embolism (PE)

6. Endocrine and Metabolic Disorders

Hyperthyroidism (thyroid storm)
Adrenal insufficiency
Gout or pseudogout

7. Heat-Related Illnesses

Heat exhaustion or heat stroke (due to prolonged exposure to high temperatures)

8. Other Causes

Post-Surgical Fever: Common after surgery due to inflammation or infection.
Alcohol or Drug Withdrawal: Can cause fever and other symptoms.
Neurological Conditions: Such as stroke or brain injury.
Periodic Fever Syndromes: Rare genetic conditions causing recurrent fevers (e.g., familial Mediterranean fever).

When to Seek Medical Attention

Seek immediate medical care if fever is accompanied by:

High fever (above 103°F or 39.4°C)
Persistent fever lasting more than 3 days
Severe headache, stiff neck, or sensitivity to light (possible meningitis)
Shortness of breath or chest pain
Confusion, seizures, or altered mental status
Rash, especially if it spreads rapidly
Signs of dehydration (e.g., dark urine, dizziness)

Diagnosis and Treatment

Diagnosis: A healthcare provider will evaluate symptoms, perform a physical exam, and may order tests (e.g., blood tests, urine tests, imaging, or cultures).
Treatment: Depends on the underlying cause. For example:
- Antibiotics for bacterial infections
- Antiviral medications for viral infections
- Anti-inflammatory drugs for autoimmune conditions
- Supportive care (e.g., hydration, rest, antipyretics like acetaminophen or ibuprofen)

Fever is a symptom, not a disease, and identifying the underlying cause is crucial for effective treatment. If you have concerns about a fever, consult a healthcare professional.