===== Infection Classification =====

Infections can be classified based on different criteria: **causative agent**, **clinical presentation**, **anatomical location**, **mode of transmission**, and **duration**.

==== 1. According to Causative Agent ====
  * **Bacterial** – *Streptococcus pneumoniae*, *Escherichia coli*, *Mycobacterium tuberculosis*
  * **Viral** – *Influenza virus*, *Herpes simplex virus*, *HIV*
  * **Fungal** – *Candida albicans*, *Cryptococcus neoformans*
  * **Parasitic** – *Plasmodium falciparum*, *Toxoplasma gondii*
  * **Prion-related** – *Creutzfeldt-Jakob disease*

==== 2. According to Anatomical Location ====
  * **Respiratory infections** – Pneumonia, bronchitis, sinusitis
  * **[[Central nervous system infection]](CNS)** – Meningitis, encephalitis, brain abscess
  * **Gastrointestinal** – Gastroenteritis, hepatitis
  * **Genitourinary** – Cystitis, pyelonephritis, STIs
  * **Skin and soft tissue** – Cellulitis, abscesses
  * **Bone and joint** – Osteomyelitis, septic arthritis

==== 3. According to Mode of Transmission ====
  * **Direct contact** – Herpes, fungal skin infections
  * **Airborne / Droplet** – Influenza, COVID-19, TB
  * **Fecal-oral** – Hepatitis A, cholera
  * **Vector-borne** – Malaria, dengue
  * **Blood-borne / Sexual** – HIV, hepatitis B & C

==== 4. According to Clinical Course ====
  * **Acute** – Rapid onset and short duration (e.g., influenza)
  * **Subacute** – Intermediate duration (e.g., subacute bacterial endocarditis)
  * **Chronic** – Long-lasting (e.g., tuberculosis, hepatitis C)
  * **Latent** – Present but asymptomatic, with potential reactivation (e.g., herpes viruses)

==== 5. According to Source ====
  * **Community-acquired** – Contracted outside healthcare settings
  * **Hospital-acquired (nosocomial)** – Acquired during hospitalization
  * **Opportunistic** – In immunocompromised hosts (e.g., HIV-related infections)

==== Summary Table ====
^ **Classification**       ^ **Examples**                                             ^
| By Agent                 | Bacterial, Viral, Fungal, Parasitic, Prions              |
| By Location              | CNS, respiratory, GI, GU, skin, bone                     |
| By Transmission          | Contact, airborne, fecal-oral, vector, blood             |
| By Clinical Course       | Acute, Subacute, Chronic, Latent                         |
| By Source                | Community-acquired, Nosocomial, Opportunistic            |