Infections

Infections are conditions in which microorganisms invade the body, multiply, and cause tissue damage or elicited immune responses. They can involve any tissue or organ and can range from asymptomatic colonization to severe illness. Infection is the presence and growth of pathogens; disease refers to the symptoms and damage that may result.

Pathogens include bacteria, viruses, fungi, and parasites. Transmission occurs through direct or indirect contact, respiratory droplets, airborne spread, vector animals, contaminated water or food, and sexual contact. Some infections are acquired in healthcare settings (nosocomial).

Clinical presentation varies by site and organism; common signs include fever, fatigue, pain, swelling, redness, or discharge. Diagnosis combines clinical examination with laboratory tests such as cultures, microscopy, molecular tests (PCR), and serology. Distinguishing infection from colonization or mere contamination is important; sepsis is a life‑threatening systemic response to infection.

Treatment depends on the causal organism. Bacterial infections are treated with antibiotics; viruses with antivirals, and fungal or parasitic infections with respective agents. Supportive care and management of complications are important. Antibiotic stewardship aims to use antimicrobials only when needed to reduce resistance. Vaccination can prevent many infections; infection control measures reduce transmission.

Prevention focuses on vaccination, hygiene, safe food and water, safe sex, and vector control. Early recognition and treatment improve outcomes; delays can lead to complications such as organ damage, sepsis, or chronic infection. Antimicrobial resistance poses a global health challenge, underscoring the need for effective prevention and appropriate therapy.