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 localized or systemic, with viral infections often involving multiple body parts and bacterial infections causing localized 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 characterized by localized 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 localized 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.
An infection is the invasion of tissues by pathogens, their multiplication, and the reaction of host tissues to the infectious agent and the toxins they produce. An infectious disease, also known as a transmissible disease or communicable disease, is an illness resulting from an infection.
| Infection | |
|---|---|
 | |
| False-colored electron micrograph showing a malaria sporozoite migrating through the midgut epithelium of a rat | |
| Specialty | Infectious diseases |
| Causes | bacterial, viral, parasitic, fungal, prion |
Infections can be caused by a wide range of pathogens, most prominently bacteria and viruses. Hosts can fight infections using their immune systems. Mammalian hosts react to infections with an innate response, often involving inflammation, followed by an adaptive response.
Specific medications used to treat infections include antibiotics, antivirals, antifungals, antiprotozoals, and antihelminthics. Infectious diseases resulted in 9.2 million deaths in 2013 (about 17% of all deaths). The branch of medicine that focuses on infections is referred to as infectious diseases.
