2025’s Texas measles outbreak is a lesson in the value of vaccines

adolescence: A transitional stage of physical and psychological development that begins at the onset of puberty, typically between the ages of 11 and 13, and ends with adulthood. People undergoing this transition are known as adolescents.

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: (adj. bacterial) 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.

cancer: Any of more than 100 different diseases, each characterized by the rapid, uncontrolled growth of abnormal cells. The development and growth of cancers, also known as malignancies, can lead to tumors, pain and death.

clinical trial: A research trial that involves people.

clot: (in medicine) A collection of blood cells (platelets) and chemicals that collect in a small region, stopping the flow of blood.

COVID-19: A name given to the disease that erupted into a massive global pandemic in 2020. It first emerged in 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.”

dehydrate: To lose a large amount of water.

develop: To emerge or to make come into being, either naturally or through human intervention, such as by manufacturing.

diarrhea: (adj. diarrheal) Loose, watery stool (feces) that can be a symptom of many types of microbial infections affecting the gut.

diphtheria: A bacterial infection where the germs produce a poison that destroys healthy tissue in the respiratory system. Within a few days, it can become hard to breathe. Other symptoms include weakness, fever and a very sore throat. If the poison enters the bloodstream it can eventually damage the heart, kidneys and nerves. There is a vaccine to prevent the disease. It is usually administered to children as part of a cocktail of vaccines that also target tetanus and pertussis (whooping cough).

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).

fatigue: The feeling of being tired, listless or short on energy.

fertility: Ability to reproduce.

flu: Short for influenza. It is a highly contagious viral infection of the respiratory passages causing fever and severe aching. It often occurs as an epidemic.

Food and Drug Administration: (or FDA) A part of the U.S. Department of Health and Human Services, FDA is charged with overseeing the safety of many products. For instance, it is responsible for making sure drugs are properly labeled, safe and effective; that cosmetics and food supplements are safe and properly labeled; and that tobacco products are regulated.

germ: Any one-celled microorganism, such as a bacterium or fungal species, or a virus particle. Some germs cause disease. Others can promote the health of more complex organisms, including birds and mammals. The health effects of most germs, however, remain unknown.

hepatitis: A potentially serious form of liver inflammation due to infection by any of several hepatitis viruses. They have been named hepatitis-A, -B, -C, -D and -E viruses.

HPV: Short for human papillomavirus. This has become the most common sexually transmitted disease in the United States. It may cause genital warts, or no symptoms at all. But once people become infected, they can later develop any of several cancers. The Centers for Disease Control and Prevention recommends that all boys and girls 11- to 12-years old should get vaccinated. For those who missed that window, CDC recommends catch-up vaccinations for males through age 21 and females through age 26.

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.

immunity: The ability of an organism to resist a particular infection or poison by providing cells to remove, kill or disarm the dangerous substance or infectious germ. Or, when used colloquially, it means the ability to avoid some other type of adverse impact (such as firing from a job or being bullied).

infection: (adj. infectious) A disease that can spread from one organism to another. It’s usually caused by some type of microbe.

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.

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.

kidney: Each in a pair of organs in mammals that filters blood and produces urine.

measles: A highly contagious disease, typically striking children. Symptoms include a characteristic rash across the body, headaches, runny nose, and coughing. Some people also develop pinkeye, a swelling of the brain (which can cause brain damage) and pneumonia. Both of the latter two complications can lead to death. Fortunately, since the middle 1960s there has been a vaccine to dramatically cut the risk of infection.

meningococcal disease: A potentially deadly disease caused by infection with Neisseria meningitides bacteria. Spread by saliva, it can be picked up through kissing or sharing a room with someone (such a camp or dorm room). Symptoms can be initially mistaken for flu, including a fever, headache, nausea, vomiting, confusion and stiff neck. If not treated in time, the germs can infect the lining of the brain and spinal cord or bloodstream.

mumps: A highly contagious childhood viral disease characterized visually by swollen cheeks and a puffy jaw due a swelling of the salivary glands. It causes flu-like symptoms, including fever, muscle aches, headaches and being very tired. It’s spread as influenza is, by sneezing, coughing or touching something contaminated with the virus, such as a patient’s hands, drinking glass or spoon. In rare cases, the disease can inflame the brain, spinal cord or other tissues or cause deafness.

muscle: A type of tissue used to produce movement by contracting its cells, known as muscle fibers. Muscle is rich in protein, which is why predatory species seek prey containing lots of this tissue.

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.

paralysis: The inability to willfully move muscles in one or more parts of the body. In some cases, nerves that carry the signal to move may have been severed or damaged. In other cases, the brain may be the source of the problem: It may fail to understand or act on a nerve’s signal to move.

pediatrician: A doctor who works in the field of medicine that has to do with children and especially child health. 

pneumonia: A lung disease in which infection by a virus or bacterium causes inflammation and tissue damage. Sometimes the lungs fill with fluid or mucus. Symptoms include fever, chills, cough and trouble breathing.

polio: An infectious viral disease that affects the central nervous system and can cause temporary or permanent paralysis.

political: (n. politics) An adjective that refers to the activities of people charged with governing towns, states, nations or other groups of people. It can involve deliberations over whether to create or change laws, the setting of policies for governed communities, and attempts to resolve conflicts between people or groups that want to change rules or taxes or the interpretation of laws. The people who take on these tasks as a job (profession) are known as politicians.

range: The full extent or distribution of something. For instance, a plant or animal’s range is the area over which it naturally exists. (in math or for measurements) The extent to which values can vary (such as the highest to lowest temperatures). Also, the distance within which something can be reached or perceived.

recall: To remember.

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.)

RSV: Short for respiratory syncytial virus. This infectious disease typically causes mild, cold-like symptoms. The exception is when it strikes infants or the elderly. In these populations, the virus can quickly bring on serious symptoms, even death.

rubella: A formerly common childhood infection sometimes called the “German” measles or three-day measles. The short-lived infection tends to cause a slight fever and rash that spreads from the face to the rest of the body. Almost half of infected people show no symptoms. The big risk is to the baby of women who get the disease during pregnancy. The child may develop deafness, vision problems, heart defects, mental retardation and liver or spleen damage.

side effects: Unintended problems or harm caused by a procedure or treatment.

strain: (in biology) Organisms that belong to the same species that share some small but definable characteristics. For example, 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.

system: A network of parts that together work to achieve some function. For instance, the blood, vessels and heart are primary components of the human body’s circulatory system. Similarly, trains, platforms, tracks, roadway signals and overpasses are among the potential components of a nation’s railway system. System can even be applied to the processes or ideas that are part of some method or ordered set of procedures for getting a task done.

tetanus: An unusual type of bacterial infection that usually does not spread between infected individuals. The source of these germs is typically exposure to soil, dust or animal feces. The disease causes stiff, painful muscles throughout the body, including a cramping in the jaw (which is why it’s sometimes called “lockjaw”). Fevers, seizures, sweating and headaches may also occur.

Texas: The second largest state in the United States, located along the southern border with Mexico. It is about 1,270 kilometers (790 miles) long and covers an area of 696,000 square kilometers (268,581 square miles).

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.

virus: Tiny infectious particles consisting of genetic material (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 many scientists argue that 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.