Infectious Diseases Overview

A disease caused by a contagious agent that transmits and causes an infection. It affects tissues and cells, leading to pathological effects.

The scientific study of infectious disease, including its causes, transmission, prevention, and treatment.

Tiny organisms that can cause infectious diseases, such as bacteria, viruses, fungi, and protozoa.

The process by which an infectious agent moves from one host to another.

The inhalation of air droplets containing microorganisms, which can cause respiratory infections.

The ingestion of contaminated food or water, which can cause food poisoning or other intestinal infections.

Direct contact with an infected individual's tissues or bodily fluids, which can cause skin infections, STIs, or other diseases.

Transmission through contaminated inanimate objects, such as doorknobs, medical equipment, or shared toys.

A bacterial capsule is a protective layer around the cell that prevents phagocytosis by the immune system.

The toxin produced by Bacillus anthracis that increases intracellular cyclic AMP levels, leading to edema and potential cell death.

A toxin released by Bacillus anthracis that activates a signaling pathway leading to excessive inflammation.

A serious bacterial infection characterized by the presence of a high number of bacteria in the bloodstream.

Observable signs of an infectious disease, such as fever, coughing, or vomiting.

Symptoms are subjective experiences of an illness, such as pain, nausea, or fatigue.

A bacterial infection caused by Bacillus anthracis, which can be spread through contact with infected animals, contaminated soil, or contaminated products. It can manifest in different forms: Cutaneous anthrax, Gastrointestinal anthrax, Inhalation anthrax and Injection anthrax.

A form of anthrax that is caused by contamination of a wound with spores from the environment or contaminated animal products.

Anthrax acquired by inhaling spores from contaminated animal products. It is the most dangerous form, with a high fatality rate.

Anthrax contracted through ingestion of spores from contaminated meat.

Anthrax that is acquired through contaminated needles or injections.

A toxin produced by Bacillus anthracis, contributing to the development of anthrax.

A protective outer shell formed by Bacillus anthracis, which allows it to survive in harsh environments.

The process by which Bacillus anthracis spores germinate within the host's body, resulting in the bacteria multiplying and spreading.

The time period between an individual's exposure to an infectious agent and the onset of the first symptoms.

Characterized by mild, non-specific symptoms that signal the beginning of a disease. They appear just before the distinct, more severe symptoms of the clinical phase.

A period when a person shows typical signs and symptoms of a specific disease. It's the most obvious phase of illness.

The phase where the severity of symptoms starts to decline, marking a shift toward recovery and symptom relief.

Final phase of recovery where symptoms have completely disappeared. Injured tissues heal, and the body regains strength.

A disease that develops rapidly and progresses quickly. Symptoms appear suddenly and intensely.

A disease that develops slowly and may not be severe but lasts for a long time.

A disease that is characterized by periods of no symptoms between outbreaks of illness. The infectious agent remains inactive in the body.

A type of inflammation characterized by the presence of pus, which is a thick, yellowish fluid containing dead white blood cells and bacteria.

A type of inflammation characterized by the formation of granulomas, which are small, round collections of immune cells that wall off the infection.

A type of inflammation characterized by the presence of fibrin, a protein that helps to form blood clots.

A type of inflammation characterized by the presence of lymphocytes, a type of white blood cell that helps to fight infection.

A diagnostic technique that uses antibodies to detect specific microorganisms in tissue samples.

A diagnostic technique that uses nucleic acid probes to detect specific microorganisms in tissue samples.

A diagnostic technique that uses high-powered microscopy to visualize the ultrastructure of microorganisms and infected tissues.

A diagnostic technique that uses polymerase chain reaction (PCR) to amplify and detect specific microbial DNA in tissue samples.

HIV infection affects the body's immune system by directly targeting and destroying CD4+ T cells, primarily in the gut mucosa, thymus, and secondary lymph nodes. This depletion of T cells weakens the immune response, making the body susceptible to opportunistic infections.

Opportunistic infections are caused by microbes that normally wouldn't cause harm in a healthy individual but can thrive in a person with a weakened immune system. Common examples include Mycobacterium tuberculosis, Toxoplasma gondii, and Cryptococcus neoformans.

The pathogenesis of infectious diseases encompasses how infectious agents cause disease. This involves mechanisms of pathogenicity, such as toxin production (e.g., by bacteria), direct cell destruction (e.g., by viruses), or triggering immune responses that lead to disease signs and symptoms.

Infectious agents follow a series of steps to cause disease: entry and attachment to the body, colonization, local or general spread, invasion of tissues and cells, replication, evasion of the immune response, and exit to transmit to new hosts.

The body's immune response can play a complex role in infectious disease. While it can be crucial for fighting off pathogens, sometimes the immune response itself can contribute to tissue damage and disease symptoms, such as fever, sneezing, and inflammation.