The National Academies: What You Need To Know About Infectious Disease

The National Academies

What You Need To Know About Infectious Disease


Adaptive Mutation

The gradual process through which certain genetic mutations that confer a specific advantage in a selective environment become more common within a population over time.


A condition in which there is a deficit in the normal number of red blood cells in the blood.

Antibiotic Resistance

The process through which pathogenic microorganisms, by way of genetic mutation, develop the ability to withstand exposure to the drugs used to eradicate them.


A class of drugs used to kill or inhibit the growth of disease-causing microorganisms. Typically antibiotics are used on bacteria, but in some cases they are also used against other microorganisms, such as fungi and protozoa.


A special type of protein found in the blood and bodily fluid that is used by the immune system to identify and neutralize foreign and harmful substances in the body, such as bacteria and viruses.

Autoimmune Disease
A condition in which the immune system mistakenly attacks healthy tissue in the body.

A taxonomic class of bacteria.


A large group of unicellular microorganisms that lack a cell nucleus. Some bacteria are pathogenic and harmful to humans, some have no effect at all on humans, and some are beneficial.

Beta-lactam Antibiotics

One of several families of antibiotics, including penicillins, cephalosporins, carbapenems, and monobactams, containing a molecular ring-shaped structure made up of three carbon atoms and one nitrogen atom.

Biological Agent (Terrorism)

A bacterium, virus, prion, fungus, or other biological toxin that is used in bioterrorism or biological warfare.


The deliberate release of viruses, bacteria, or other biological agents to cause illness and death in people, animals, or plants.


A bacterium, virus, prion, fungus, or other biological toxin that is used in bioterrorism or biological warfare.

Bronchial Tubes

Large tubes that carry air into smaller branches of the lungs after the air has passed through the mouth, nasal passages, and windpipe.


A class of diseases in which abnormal cells divide without control and are able to invade healthy tissues in various parts of the body.

Category A Agents

A class of biological agents that the Centers for Disease Control and Prevention views as posing the highest priority risk to U.S. national security.


The smallest unit of living matter capable of functioning independently.

Cell Membrane

A semipermeable barrier that separates the interior of a cell from the external environment.

Centers for Disease Control and Prevention (CDC)

A federal agency under the Department of Health and Human Services that works with partners across the United States to ensure public health—through health promotion; prevention of disease, injury, and disability; and preparedness for new health threats.


An organized structure of DNA and proteins within the nucleus of a cell that contains many genes and regulatory elements.

Chronic Disease

Any disease that is long lasting or recurrent, as opposed to an acute disease.

Chronic Inflammation

A prolonged form of localized immune response to harmful agents and damaged tissue that is characterized by redness, swelling, heat, and/or pain.


A condition caused by chronic liver disease characterized by the development of scar tissue leading to a loss of liver function.

Climate Change

The process of shifting from one prevailing state in regional or global climate to another. Climate change is typically the preferred term over “global warming” because it helps to convey that the characteristics of climate change are not limited to rising temperatures.


A general term for any disease-causing infectious agent.


A type of protein secreted by cells in the immune system that carries signals used to communicate locally between cells.


Any abnormal condition in which cells in the body are damaged and symptoms of illness begin to appear.


Short for deoxyribonucleic acid, DNA is any of the nucleic acids that contain the genetic instructions necessary for the development and functioning of all living organisms as well as some viruses.


A branch of science that deals with the relations of organisms to one another and their physical environment.


A functional unit that consists of all the living organisms in a particular area, including the nonliving, physical components in the environment with which the organisms interact, such as air, soil, water, and sunlight.

Egg Cell

The female gamete, or sex cell, which carries the hereditary material of the female parent and unites with the male sperm cell during sexual reproduction.

El NiƱo-Southern Oscillation Cycle (ENSO)
An irregular event that disrupts regional and global weather patterns when unusually warm surface water flows across the Pacific Ocean toward and along the coast of South America, preventing the upwelling of nutrient-rich, cold deepwater.

Inflammation of the brain.


Restricted to a particular area or region.


An event that occurs when the incidence of new cases of a certain disease, over a given period of time, substantially exceeds what is expected in a specific population.


The change in heritable traits in a population of organisms over successive generations.


An external skeleton that protects and supports an organism, in contrast to an internal endoskeleton.

Fertilized Egg

Sometimes referred to as a zygote, this is the resulting initial cell formed when a sperm cell unites with an egg cell.


A taxonomic Kingdom of spore-forming organisms distinct from plants, animals, and bacteria that includes microorganisms such as yeast and molds, as well as more familiar mushrooms.

Gastrointestinal Tract

The structure in the body through which food is ingested, broken down, and absorbed to provide the body with nutrients, and waste products are excreted.


A specific sequence of nucleotides in either DNA or RNA that serves a functional unit of inheritance in a living organism, controlling the transmission and expression of one or more traits.


A branch of biology that studies heredity and variation in organisms.


In the context of microbiology, a microorganism that causes disease.

Germ Theory

A theory in medicine that microorganisms are the causative agents of infections, contagious diseases, and various other conditions.


The process by which regional economies, societies, and cultures are becoming integrated through a global network of trade, migration, communication, and the spread of new technology.


The specific geographical area or physical environment that is inhabited by an organism or a population of organisms.


An organism that harbors a parasite or another organism where there is a commensal or mutually beneficial relationship.

Immune System

The system of biological structures and processes that protects the body from foreign substances, including pathogens.


The process of strengthening the body’s defense against a particular infectious agent.

Incubation Time

The period of time between exposure to an infectious agent and the appearance of symptoms of the infection or disease it causes.


The entry, establishment, and replication of pathogens inside a host organism.

Infectious Disease

A type of illness caused by a pathogenic agent, including viruses, bacteria, fungi, protozoa, parasites, or abnormal proteins known as prions.

Institute of Medicine
An independent, nonprofit organization that works outside of government to provide unbiased and authoritative advice on health and medicine to decision makers and the public.

A type of protein produced by white blood cells that blocks viruses from reproducing.


Anything occurring within or entering by way of a vein.

Latent Infection

A type of persistent viral infection in which the virus is not currently producing additional viral offspring, but could later be reactivated and begin producing copies of the virus without the host being re-infected.


A broad group of molecules including fats and waxes that are insoluble in water.

Meningeal Infection

An infection of the protective membranes that cover the brain and spinal cord, known collectively as the meninges.

The sum total of chemical reactions that occur within a living cell both to build new molecules within the cell and break down and assimilate sources of energy for the cell.

Sometimes referred to as a microorganism, a microbe is an organism that is microscopic and thus invisible to the naked eye. 


The relative occurrence of a disease or condition that causes illness.


The number of deaths in a given time or place.

Mucous Membrane

A special membrane full of mucous glands which lines body passages and internal cavities involved with absorption and secretion of substances.


A change in the sequence of DNA in a cell’s genome that can be caused by radiation, viruses, certain types of chemicals, and errors that occur during cell division and DNA replication.


A unit of length equal to one one-billionth (1 X 10-9) of a meter.

National Institute of Allergy and Infectious Diseases (NIAID)

Part of the U.S. Department of Health and Human Services and the National Institutes of Health, NIAID conducts and supports basic and applied research to better understand, treat, and ultimately prevent infectious, immunologic, and allergic diseases.

Natural Selection

The process by which certain heritable traits that contribute to the survival and reproductive success of an organism become more widespread within a population over successive generations.

Nerve Toxin

A toxin that acts specifically on the nervous system.


A living being.


An unexpected increase in the incidence of a particular disease over a given time period and geographic range. A general term that may refer either to an epidemic or a pandemic.


An increase in the occurrence of a particular disease over a very large region, such as a continent or the entire globe, that is greater than what is expected over a given period of time.


A close relationship between two organisms in which one organism, the parasite, benefits at the expense of the host organism.


A biological agent that causes disease.

Peptic Ulcer
An open sore that develops on the inner lining of the stomach, esophagus, or upper small intestine.

A ring of DNA usually found in bacteria that is separate from and can replicate independently from DNA in a chromosome.

A causative agent of infectious disease that is composed primarily of protein.
A type of complex organic compound made up of amino acids linked together by peptide bonds that performs a variety of essential functions in living organisms.

A taxonomic group of single-celled microorganisms that live in almost every kind of habitat and include some pathogenic parasites of humans and other animals. 

Recombinant Technology

The process that allows technicians to create artificial pieces of DNA in which two or more DNA sequences, often from separate organisms, are combined in ways that would not normally occur naturally.


The process of producing a copy of a strand of DNA or RNA.

The process by which parent organisms create new offspring by either sexual or asexual means.

An organism in which a parasite that is pathogenic for some other organism lives and reproduces without harming its host.

Respiratory Tract

The part of the anatomy that has to do with respiration, including the nasal passages, trachea, and lungs.

Rheumatic Fever

An inflammatory disease that may be caused by an untreated or improperly treated case of strep throat.


A type of virus that is responsible for causing upper respiratory tract infections in humans, otherwise known as the common cold.


Short for ribonucleic acid, RNA is a type of single-stranded molecule of nucleic acids that contains ribose and is responsible for controlling a number of chemical activities within cells.


A serious mental illness characterized by the presence of hallucinations, delusions, disorganized speech or thinking, a loss of contact with reality, and a noticeable deterioration of functioning in everyday life.

Skin Lesion

Any abnormal tissue on the skin caused by injury or disease.


One of the most basic units of biological classification, ranking just below the genus and comprising individuals or populations capable of interbreeding.

Sperm Cell

The male gamete, or sex cell, which carries the hereditary material of the male parent and unites with the female egg cell during sexual reproduction.

Staph Infection

An infection caused by any one of several harmful species or subspecies of bacteria of the genus Staphylococcus.


The process of destroying all forms of life, including infectious agents, from a surface, fluid, or biological medium with the use of heat, chemicals, irradiation, high pressure, filtration, or some combination of these methods.


A genetic variant or specific subtype of microorganism or virus.


The process of land conversion and development around the periphery of major cities.


A subjective indication of the presence of disease or a departure from the body’s normal state of functioning. 

Tissue Culture

The process by which tissues are intentionally grown under controlled conditions.


A poisonous substance produced by the metabolic processes of living cells or organisms.


The main trunk of the network of tubes that carries air to and from the lungs, sometimes referred to as the “windpipe.”

Transition Zone

The area encompassing the edges of two distinct ecosystems, such as the area where a forest intersects with grassland.

Universal Flu Vaccine

A vaccine that is effective against all forms of the influenza virus.

Urogenital Disease

Disease of the organs that function in excretion of fluids and reproduction.


A biological preparation that improves the immune system’s ability to recognize and destroy harmful infectious agents.


An organism (usually an arthropod such as a flea, mosquito, or tick) that carries an infectious agent from reservoir to host.


An infectious agent that is only capable of replicating itself inside the living cells of other organisms.

White Blood Cell

A special type of cell that works as part of the immune system to defend the body against disease and infection.

World Health Organization (WHO)

The directing and coordinating authority for health within the United Nations system, responsible for providing leadership on global health matters, shaping the health research agenda, setting norms and standards, articulating evidence-based policy options, providing technical support to countries and monitoring and assessing health trends.


A broad group of microscopic fungi that includes harmless forms of yeast used in baking and alcoholic fermentation as well as pathogenic species that can cause disease. 


Any disease that can be transmitted from non-human animals to humans.

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What do you know about infectious disease?

True or False: Infection with a pathogen (a disease-causing microbe) does not necessarily lead to disease.

  • Correct!

    Infection occurs when viruses, bacteria, or other microbes enter your body and begin to multiply. Disease follows when the cells in your body are damaged as a result of infection, and signs and symptoms of an illness appear.

  • Sorry, that’s incorrect.

    Infection occurs when viruses, bacteria, or other microbes enter your body and begin to multiply. Disease follows when the cells in your body are damaged as a result of infection, and signs and symptoms of an illness appear.