Types of Infections - Bacterial infections caused by pathogens such as Mycobacterium tuberculosis, Staphylococcus aureus, Escherichia coli, Clostridium botulinum, and Salmonella spp. - Viral infections caused by pathogens such as HIV, Rhinovirus, Lyssaviruses (e.g., Rabies virus, Ebolavirus), and Severe acute respiratory syndrome coronavirus 2 - Fungal infections including yeasts like Candida, filamentous fungi like Aspergillus, Pneumocystis species, and dermatophytes - Parasitic infections caused by unicellular organisms like malaria and Toxoplasma, and macroparasites like nematodes, tapeworms, and flukes - Infections caused by arthropods such as ticks, mites, fleas, and lice, often referred to as infestations - Prion infections, although they do not secrete toxins

Signs and Symptoms of Infections - General symptoms of infection include fatigue, loss of appetite, weight loss, fevers, night sweats, chills, aches, and pains - Specific symptoms can affect individual body parts, such as skin rashes, coughing, or a runny nose - Some infectious diseases may be asymptomatic or cause no illness in a host - Infections can be localised or systemic, with viral infections often involving multiple body parts and bacterial infections causing localised redness, heat, swelling, and pain - Pus and milky-colored liquid are signs of infection in wounds

Bacterial vs. Viral Infections - It can be difficult to distinguish between bacterial and viral infections based on symptoms alone - Viral infections are often systemic, involving multiple body parts, while bacterial infections are characterised by localised pain and symptoms - Antibiotics can cure bacterial infections, but they are ineffective against viral infections - Viral infections can cause itching or burning sensations, while bacterial infections may produce pus and localised pain - Pain on one side of the throat or in one ear is more indicative of a bacterial infection

Pathophysiology of Infections - Infections follow a chain of events called the chain of infection or transmission chain - The chain includes the infectious agent, reservoir, entry into a susceptible host, exit, and transmission to new hosts - Each step must occur in order for an infection to develop - Health care workers target the chain of infection to prevent and treat infections - Colonization is the initial stage of infection, where organisms successfully enter the body, grow, and multiply

Diagnosis of Infectious Diseases - Medical history and physical examination - Culture of infectious agents - Microscopic examination and detection of pathogen-produced substances - Tests for antigens or antibodies in body fluids - Imaging techniques (X-rays, CAT scans, etc.) for internal abnormalities - Presenting symptoms aid in diagnosis - Pathognomonic signs are rare but indicative of a specific disease - Not all infections are symptomatic - Certain symptoms in children increase the risk of serious infection - Additional diagnostic techniques are often required to confirm suspicions - Microbiological culture is used to isolate a pathogen from a clinical specimen - Microscopy is an important tool in the diagnosis of infectious diseases - Biochemical tests detect metabolic or enzymatic products characteristic of infectious agents - Animal culture and xenodiagnosis can be used for identification of certain pathogens - PCR-based diagnostics are becoming the gold standard for diagnosing infectious agents - Metagenomic sequencing is a promising diagnostic test for identifying the cause of infection - Diagnostic tests are indicated when they can aid in treatment or prevention of a disease - Symptomatic infections, inapparent infections, latent infections, acute infections, chronic infections, and subacute infections are different classifications of infections.