allergy: The inappropriate reaction by the body’s immune system to a normally harmless substance. Untreated, a particularly severe reaction can lead to death.
antibodies: Any of a large number of proteins that the body produces from B cells and releases into the blood supply as part of its immune response. The production of antibodies is triggered when the body encounters an antigen, some foreign material. Antibodies then lock onto antigens as a first step in disabling the germs or other foreign substances that were the source of those antigens.
bacteria: (singular: bacterium) Single-celled organisms. These dwell nearly everywhere on Earth, from the bottom of the sea to inside other living organisms (such as plants and animals). Bacteria are one of the three domains of life on Earth.
blood-brain barrier: A barrier of tightly packed cells that carefully regulate what molecules can — and can’t — enter the brain. The barrier protects the brain from foreign substances in the blood and helps to maintain a constant environment for brain cells.
cell: The smallest structural and functional unit of an organism. Typically too small to see with the unaided eye, it consists of a watery fluid surrounded by a membrane or wall. Depending on their size, animals are made of anywhere from thousands to trillions of cells. Most organisms, such as yeasts, molds, bacteria and some algae, are composed of only one cell. (
coronavirus: A family of viruses named for the crown-like spikes on their surface (corona means “crown” in Latin). Coronaviruses cause the common cold. The family also includes viruses that cause far more serious infections, including SARS and COVID-19.
COVID-19: A name given to the disease that caused a massive global outbreak. It first emerged in December 2019 and is caused by a new coronavirus known as SARS-CoV-2. Symptoms can include pneumonia, trouble breathing, feeling too tired to walk more than a few steps, fever, headaches, low blood-oxygen levels, blood clots and brain “fog.”
develop: To emerge or to make come into being, either naturally or through human intervention, such as by manufacturing.
emerging infectious disease: A disease that suddenly has begun infecting increasing numbers of people or other organisms and could increase dramatically, more so in the near future.
encephalitis: An inflammation of the brain, usually caused by a viral infection. The disease can impair movement, clarity of thinking and other facets of brain function. In severe cases, this condition can lead to death.
environment: The sum of all of the things that exist around some organism or the process and the condition those things create. Environment may refer to the weather and ecosystem in which some animal lives, or, perhaps, the temperature and humidity (or even the placement of things in the vicinity of an item of interest).
epidemic: A widespread outbreak of an infectious disease that sickens many people (or other organisms) in a community at the same time. The term also may be applied to non-infectious diseases or conditions that have spread in a similar way.
evolution: (v. to evolve) A process by which species undergo changes over time, usually through genetic variation and natural selection. These changes usually result in a new type of organism better suited for its environment than the earlier type. The newer type is not necessarily more “advanced,” just better adapted to the particular conditions in which it developed. Or the term can refer to changes that occur as some natural progression within the non-living world (such as computer chips evolving to smaller devices which operate at an ever faster speed).
focus: (in behavior) To look or concentrate intently on some particular point or thing.
genetic: Having to do with chromosomes, DNA and the genes contained within DNA. The field of science dealing with these biological instructions is known as genetics. People who work in this field are geneticists.
host: (in biology and medicine) The organism (or environment) in which some other thing resides. Humans may be a temporary host for food-poisoning germs or other infective agents. (v.) The act of providing a home or environment for something.
immune system: The collection of cells and their responses that help the body fight off infections and deal with foreign substances that may provoke allergies.
impair: (n. impairment) To damage or weaken in some way.
infect: To spread a disease from one organism to another. This usually involves introducing some sort of disease-causing germ to an individual.
infection: (adj. infectious) A disease that can spread from one organism to another. It’s usually caused by some type of germ.
inflammation: (adj. inflammatory) The body’s response to cellular injury and obesity; it often involves swelling, redness, heat and pain. It also is an underlying feature responsible for the development and aggravation of many diseases, especially heart disease and diabetes.
mutation: (v. mutate) Some change that occurs to a gene in an organism’s DNA. Some mutations occur naturally. Others can be triggered by outside factors, such as pollution, radiation, medicines or something in the diet. A gene with this change is referred to as a mutant.
National Institute of Allergy and Infectious Diseases: Initially created as a small lab in 1887 at a hospital in New York City, it now is headquartered in Bethesda, Md. Developed to explore the new science of bacteriology, it became part of the National Institutes of Health in 1948. Today it works to better understand, treat and prevent all types of infectious and immunity-affecting diseases.
organism: Any living thing, from elephants and plants to bacteria and other types of single-celled life.
pandemic: An epidemic that affects a large proportion of the population across a country or the world.
physical: (adj.) A term for things that exist in the real world, as opposed to in memories or the imagination. It can also refer to properties of materials that are due to their size and non-chemical interactions (such as when one block slams with force into another).
primary: An adjective meaning major, first or most important. (In reference to colors). The basic hues that can combine to make all other colors. For mixing light, the primary colors are red, green, and blue. (in elections) A preliminary, early U.S. election to select a limited number of candidates (typically one for each open office) who will represent their political party on the printed ballot in an upcoming national election.
rabies: A virus that is transmitted from mammals such as bats, raccoons, skunks and dogs — sometimes to people. Rabies is found on every continent except Antarctica, and is spread by contact with the saliva of an infected host. A vaccine exists. Without a vaccination, nearly every infected person will die.
replication: (in biology) The copying of genetic material as a microbe or virus begins to reproduce. (in experimentation) Getting the same result as an earlier test or experiment — often an earlier test performed by someone else. Replication depends upon repeating every step of a test, step by step. If a repeated experiment generates the same result as in earlier trials, scientists view this as verifying that the initial result is reliable. If results differ, the initial findings may fall into doubt. Generally, a scientific finding is not fully accepted as being real or true without replication.
reservoir: A large store of something. Lakes are reservoirs that hold water. People who study infections refer to the environment in which germs can survive safely (such as the bodies of birds or pigs) as living reservoirs.
social distancing: A term for the intentional separation of people to limit the chance that a disease can be passed from one to another.
species: A group of similar organisms capable of producing offspring that can survive and reproduce.
spinal cord: A cylindrical bundle of nerve fibers and associated tissue. It is enclosed in the spine and connects nearly all parts of the body to the brain, with which it forms the central nervous system.
strain: (in biology) Organisms that belong to the same species that share some small but definable characteristics. For example, biologists breed certain strains of mice that may have a particular susceptibility to disease. Certain bacteria or viruses may develop one or more mutations that turn them into a strain that is immune to the ordinarily lethal effect of one or more drugs.
therapy: (adj. therapeutic) Treatment intended to relieve or heal a disorder.
tissue: Made of cells, it is any of the distinct types of materials that make up animals, plants or fungi. Cells within a tissue work as a unit to perform a particular function in living organisms. Different organs of the human body, for instance, often are made from many different types of tissues.
transmit: (n. transmission) To send or pass along.
vaccine: (v. vaccinate) A biological mixture that resembles a disease-causing agent. It is given to help the body create immunity to a particular disease. The injections used to administer most vaccines are known as vaccinations.
variant: A version of something that may come in different forms. (in biology) Members of a species that possess some feature (size, coloration or lifespan, for example) that make them distinct. (in genetics) A gene having a slight mutation that may have left its host species somewhat better adapted for its environment.
virus: Tiny infectious particles consisting of RNA or DNA surrounded by protein. Viruses can reproduce only by injecting their genetic material into the cells of living creatures. Although scientists frequently refer to viruses as live or dead, in fact no virus is truly alive. It doesn’t eat like animals do, or make its own food the way plants do. It must hijack the cellular machinery of a living cell in order to survive.
World Health Organization: An agency of the United Nations, established in 1948, to promote health and to control communicable diseases. It is based in Geneva, Switzerland. The United Nations relies on the WHO for providing international leadership on global health matters. This organization also helps shape the research agenda for health issues and sets standards for pollutants and other things that could pose a risk to health. WHO also regularly reviews data to set policies for maintaining health and a healthy environment.