bat: A type of winged mammal comprising more than 1,100 separate species — or one in every four known species of mammal.

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.

chemical: A substance formed from two or more atoms that unite (bond) in a fixed proportion and structure. For example, water is a chemical made when two hydrogen atoms bond to one oxygen atom. Its chemical formula is H₂O. Chemical also can be an adjective to describe properties of materials that are the result of various reactions between different compounds.

colleague: Someone who works with another; a co-worker or team member.

component: Something that is part of something else (such as pieces that go on an electronic circuit board or ingredients that go into a cookie recipe).

corona: The envelope of the sun (and other stars). The sun’s corona is normally visible only during a total solar eclipse, when it is seen as an irregularly shaped, pearly glow surrounding the darkened disk of the moon.

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.

diagnose: To analyze clues or symptoms in the search for their cause. The conclusion usually results in a diagnosis — identification of the causal problem or disease.

DNA: (short for deoxyribonucleic acid) A long, double-stranded and spiral-shaped molecule inside most living cells that carries genetic instructions. It is built on a backbone of phosphorus, oxygen, and carbon atoms. In all living things, from plants and animals to microbes, these instructions tell cells which molecules to make.

emergency room: Also known as the ER. It’s that part of the hospital where doctors initially attend to the immediate medical needs of accident victims and others who need critical care.

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.

infect: (n. infection) To spread a disease from one organism to another. This usually involves introducing some sort of disease-causing germ to an individual.

infectious: An adjective that describes a type of germ that can be transmitted to people, animals or other living things.

influenza: (also known as flu) A highly contagious viral infection of the respiratory passages causing fever and severe aching. It often occurs as an epidemic.

journal: (in science) A publication in which scientists share their research findings with experts (and sometimes even the public). Some journals publish papers from all fields of science, technology, engineering and math, while others are specific to a single subject.

kin: Family or relatives (sometimes even distant ones).

MERS: Short for Middle East respiratory syndrome. Caused by a coronavirus, this extremely infectious disease can produce fever, cough and shortness of breath. About 3 or 4 in every 10 infected patients may die. The first known outbreak occurred in 2012, when it killed some 800 people. Camels (the one-humped type) may have first introduced the disease to people.

novel: Something that is clever or unusual and new, as in never seen before.

outbreak: The sudden emergence of disease in a population of people or animals. The term may also be applied to the sudden emergence of devastating natural phenomena, such as earthquakes or tornadoes.

protein: A compound made from one or more long chains of amino acids. Proteins are an essential part of all living organisms. They form the basis of living cells, muscle and tissues; they also do the work inside of cells. Among the better-known, stand-alone proteins are the hemoglobin (in blood) and the antibodies (also in blood) that attempt to fight infections. Medicines frequently work by latching onto proteins.

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.

respiratory: Of or referring to parts of the body involved in breathing (called the respiratory system). It includes the lungs, nose, sinuses, throat and other large airways.

risk: The chance or mathematical likelihood that some bad thing might happen. For instance, exposure to radiation poses a risk of cancer. Or the hazard — or peril — itself. (For instance: Among cancer risks that the people faced were radiation and drinking water tainted with arsenic.)

RNA: A molecule that helps “read” the genetic information contained in DNA. A cell’s molecular machinery reads DNA to create RNA, and then reads RNA to create proteins.

SARS: (short for severe acute respiratory syndrome) An infectious disease that emerged in 2002 and quickly spread to infect more than 8,000 people, killing nearly 800 of them.

species: A group of similar organisms capable of producing offspring that can survive and reproduce.

transmit: (n. transmission) To send or pass along.

virology: The scientific study of viruses and the diseases they cause. The scientists who work in this field are known as virologists.

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.