Absorption: The process of taking in. For a person or an animal, absorption is the process of a substance gettin
Acute: Occurring over a short time [compare with chronic].
Acute Disease: An acute disease is a disease with either a rapid onset or a short duration, or both. Acute is NOT s
Acute Exposure: Contact with a substance that occurs once or for only a short time (up to 14 days) [compare with int
Addisons Disease: A disease characterized by severe weakness, low blood pressure, and a bronzed coloration of the skin
Additive Effect: A biologic response to exposure to multiple substances that equals the sum of responses of all the i
Adverse Health Effect: A change in body function or cell structure that might lead to disease or health problems
Ague: Malarial or intermittent fever characterized by paroxysms (stages of chills, fever, and sweating at
Ague-Cake: A form of enlargement of the spleen, resulting from the action of malaria on the system.
Amplification: Adding a species to a community increases the total abundance of hosts for a pathogen, increasing th
Analyte: A substance measured in the laboratory. A chemical for which a sample (such as water, air, or blood)
Analytic Epidemiologic Study: A study that evaluates the association between exposure to hazardous substances and disease by testi
Antagonistic Effect: A biologic response to exposure to multiple substances that is less than would be expected if the kn
Antibiotic: A chemical substance that kills or suppresses the growth of microorganisms. Antibiotics are designe
Antibiotic Resistance: The ability of a microorganism to withstand the effects of an antibiotic.
Antibody: Proteins that are found in blood of vertebrates, and are used by the immune system to identify and n
Antigen: A molecule that can stimulate an immune response.
Antigen Drift: The random accumulation of mutations in viral genes recognized by the immune system. Such accumulat
Antiviral: A chemical substance that kills or suppresses the growth of viruses. Antivirals are designed to be t
Aquired Immune Deficiency Syndrome (AIDS): An infectious disease caused by the Human Immunodeficiency Virus (HIV). Transmission occurs via one
Asymptomatic: Individuals who are infected by a disease but do not show any of the typical symptoms.
Attenuated: Reducing the virulence of an organism, usually a virus, whilst keeping it viable.
Background Level: An average or expected amount of a substance or radioactive material in a specific environment, or t
BCG: Bacille Calmette-Guérin (BCG) is a vaccine against tuberculosis that is prepared from a strain of t
Beta-Lactam Antibiotics: A broad class of antibiotics which include penicillin and its derivatives. They are the most widely
Bilious Fever: A term loosely applied to certain intestinal and malarial fevers. See typhus.
Biliousness: A complex of symptoms comprising nausea, abdominal discomfort, headache, and constipation--formerly
Biodegradation: Decomposition or breakdown of a substance through the action of microorganisms (such as bacteria or
Biologic Indicators Of Exposure Study: A study that uses (a) biomedical testing or (b) the measurement of a substance [an analyte], its met
Biologic Monitoring: Measuring hazardous substances in biologic materials (such as blood, hair, urine, or breath) to dete
Biologic Uptake: The transfer of substances from the environment to plants, animals, and humans.
Biomedical Testing: Testing of persons to find out whether a change in a body function might have occurred because of ex
Biota: Plants and animals in an environment. Some of these plants and animals might be sources of food, clo
Black Death: (1347-1351) One of the most deadly pandemics in human history, widely thought to have been caused by
Body Burden: The total amount of a substance in the body. Some substances build up in the body because they are s
Boil: An abscess of skin or painful inflammation of the skin or a hair follicle usually caused by a staphy
Bolivian Hemorrhagic Fever: A zoonotic infectious disease of man caused by a virus and transmitted to man via rodents.
Borrelia Burgdorferi: The bacterial causative agent of Lyme disease.
Broad Street Outbreak: (1854) The London Cholera outbreak investigated by John Snow that was the first epidemiological inv
Bronchial Asthma: A disorder of breathing, characterized by spasm of the bronchial tubes of the lungs, wheezing, and d
Buboe: Infected lymph nodes associated with the bubonic plague.
Bubonic Plague: A zoonotic disease vectored by fleas. Rodents form the reservoir species.
Cancer: A malignant and invasive growth or tumor. In the nineteenth century, cancerous tumors tended to ulce
Cancer Risk: A theoretical risk for getting cancer if exposed to a substance every day for 70 years (a lifetime e
Cancrum Otis: A severe, destructive, eroding ulcer of the cheek and lip. In the last century it was seen in delica
Carrier: An infected individual who shows no obvious signs of clinical disease but can infect other susceptib
CAS Registry Number: A unique number assigned to a substance or mixture by the American Chemical Society Abstracts Servic
Case Definition: A case definition is the method by which public health professionals define who is included as a cas
Case Study: A medical or epidemiologic evaluation of one person or a small group of people to gather information
Case-Control Study: A study that compares exposures of people who have a disease or condition (cases) with people who do
Catarrh: Inflammation of a mucous membrane, especially of the air passages of the head and throat, with a fre
Central Nervous System: The part of the nervous system that consists of the brain and the spinal cord.
Cholera: An infectious disease caused by the bacterium Vibrio cholerae. Transmission to humans occurs through
Cholera El Tor: El Tor is the name given to a particular strain of the Vibrio cholera bacterium, the causative agent
Cholera Infantum: A common, noncontagious diarrhea of young children, occurring in summer or autumn. It was common amo
Chorea: Any of several diseases of the nervous system, characterized by jerky movements that appear to be we
Chronic Disease: A disease that is long-lasting or recurrent.
Chronic Exposure: Contact with a substance that occurs over a long time (more than 1 year) [compare with acute exposur
Clostridium Perfringens: A ubiquitous soil bacteria that can cause a deadly infection known as gas gangrene when it infects w
Cluster Investigation: A review of an unusual number, real or perceived, of health events (for example, reports of cancer)
Coinfection: Simultaneous infection with two or more different diseases. In virology the term is used to describe
Colic: Paroxysmal pain in the abdomen or bowels. Infantile colic is benign paroxysmal abdominal pain during
Common Source Epidemic: A common source epidemic occurs when a group of people is exposed to a single common source of infec
Community Assistance Panel (CAP): A group of people from a community and from health and environmental agencies who work with ATSDR to
Comparison Value (CV): Calculated concentration of a substance in air, water, food, or soil that is unlikely to cause harmf
Competence (For Bacteria): The ability of a cell to take up extracellular ('naked') DNA from its environment.
Competence (For Hosts): The efficiency with which a host acquires and spreads a pathogen.
Complex Life Cycle: A parasite that requires multiple different host species to complete its life cycle.
Comprehensive Environmental Response Compensation And Liability Act Of 1980 (CERCLA): CERCLA, also known as Superfund, is the federal law that concerns the removal or cleanup of hazardou
Concentration: The amount of a substance present in a certain amount of soil, water, air, food, blood, hair, urine,
Congestion: An excessive or abnormal accumulation of blood or other fluid in a body part or blood vessel. In con
Conjugation: The transfer of genetic material between bacteria through direct cell-to-cell contact
Consumption: A wasting away of the body; formerly applied especially to pulmonary tuberculosis
Contaminant: A substance that is either present in an environment where it does not belong or is present at level
Continuous Epidemic: A continuous epidemic occurs when a group of people is exposed to a single common source of infectio
Convulsions: Severe contortion of the body caused by violent, involuntary muscular contractions of the extremitie
Croup: Any Obstructive Condition Of The Larynx (Voice Box) Or Trachea (Windpipe), Characterized By A Hoarse
Cyst (Bacteria): A resting or dormant stage in bacteria.
Cytokine: A substance that is produced by cells of the immune system and can affect the immune response.
Cytokine Storm: A potentially fatal immune reaction caused by highly elevated levels of various cytokines
Dead End Host: A host from which infectious agents are not transmitted to other susceptible hosts
Debility: Abnormal bodily weakness or feebleness; decay of strength. This was a term descriptive of a patient'
Definitive Host: The host in which the sexual reproduction of a parasite takes place
Delayed Health Effect: A disease or an injury that happens as a result of exposures that might have occurred in the past.
Dermal: Referring to the skin. For example, dermal absorption means passing through the skin.
Descriptive Epidemiology: The study of the amount and distribution of a disease in a specified population by person, place, an
Detection Limit: The lowest concentration of a chemical that can reliably be distinguished from a zero concentration.
Dilution: Adding a species to a community decreases the abundance of more competent hosts, decreasing the dise
Diphtheria: An acute infectious disease acquired by contact with an infected person or a carrier of the disease.
Disease Prevention: Measures used to prevent a disease or reduce its severity.
Disease Registry: A system of ongoing registration of all cases of a particular disease or health condition in a defin
DNA Virus: A virus that has DNA as its genetic material and replicates using a DNA-dependent DNA polymerase.
Dose (Not Radioactive): The amount of a substance to which a person is exposed over some time period. Dose is a measurement
Dose (Radioactive Chemicals): The radiation dose is the amount of energy from radiation that is actually absorbed by the body. Thi
Dose-Response Relationship: The relationship between the amount of exposure [dose] to a substance and the resulting changes in b
Dropsy: A contraction for hydropsy. The presence of abnormally large amounts of fluid. Congestive heart fail
Dysentery: A term given to a number of disorders marked by inflammation of the intestines (especially of the co
Ebola: Ebola is the common term for a group of viruses belonging to the genus Ebolavirus in the family Fil
Eclampsia: A form of toxemia (toxins--or poisons--in the blood) accompanying pregnancy. See dropsy.
Ecosystem Service: The quantifiable services that an ecosystem provides to humans.
Effluvia: Exhalations. In the mid-nineteenth century, they were called 'vapours' and distinguished into the co
Emerging Infectious Disease (EID): A disease that has been recently discovered, recently increased in incidence, geography, or host ran
Endemic: The constant presence of a disease or infectious agent within a given geographic area.
Endogenous Retrovirus: Integrated retroviruses derived from infection of the germline (egg or sperm) of an ancestral organi
Environmental Media: Soil, water, air, biota (plants and animals), or any other parts of the environment that can contain
Environmental Media And Transport Mechanism: Environmental media include water, air, soil, and biota (plants and animals). Transport mechanisms m
Epidemic: The occurrence in an area of a disease or illness in excess of what may be expected on the basis of
Epidemic Curve: A histogram that describes an outbreak of disease by plotting the number of cases of a disease by da
Epidemiology: The branch of medicine that deals with the study of the causes, distribution, and control of disease
Epidemiology: The study of the distribution and determinants of disease or health status in a population; the stud
Epilepsy: A disorder of the nervous system, characterized either by mild, episodic loss of attention or sleepi
Epizootic: The term used for an epidemic that occurs within an animal population.
Eukarytote: An organism whose cells contain a true nucleus, such as a plants, animals, fungi and protozoa (cf pr
Evolution: A change in the inherited traits of a population from one generation to the next.
Exposure: Contact with a substance by swallowing, breathing, or touching the skin or eyes. Exposure may be sho
Exposure Assessment: The process of finding out how people come into contact with a hazardous substance, how often and fo
Exposure Investigation: The collection and analysis of site-specific information and biologic tests (when appropriate) to de
Exposure Pathway: The route a substance takes from its source (where it began) to its end point (where it ends), and h
Exposure Registry: A system of ongoing followup of people who have had documented environmental exposures.
Exposure-Dose Reconstruction: A method of estimating the amount of people's past exposure to hazardous substances. Computer and ap
Feasibility Study: A study by EPA to determine the best way to clean up environmental contamination. A number of factor
Filovirus: A family of RNA viruses that target primates. There are two genera: the Ebola virus and Marburg viru
Fomite: An inanimate object capable of carrying infectious organisms and hence transferring them from one in
Gangrene: Death and decay of tissue in a part of the body--usually a limb--due to injury, disease, or failure
Gas Gangrene: A very unpleasant way to die. Gas gangrene is a deadly bacterial infection usually caused by Clostri
Gene: A unit of heredity. (Or a locatable region of genomic sequence, corresponding to a unit of inheritan
Genotype: A description of the genetic constitution of an individual.
Geographic Information System (GIS): A mapping system that uses computers to collect, store, manipulate, analyze, and display data. For e
Germ Theory: The theory that microorganisms are the cause of many diseases. Highly controversial when first propo
Golden Age Of Microbiology: (dates vary ~ 1850-1890) A period of tremendous advances in microbiology with consequences for epide
Grand Rounds: Training sessions for physicians and other health care providers about health topics.
Gravel: A disease characterized by small stones which are formed in the kidneys, passed along the ureters to
Great Stink: (1858) The Great Stink or The Big Stink was a time in the summer of 1858 during which the smell of u
Groundwater: Water beneath the earth's surface in the spaces between soil particles and between rock surfaces [co
H5N1: A subtype of the Influenza A virus which can cause illness in humans and many other animal species.
Half-Life: The time it takes for half the original amount of a substance to disappear. In the environment, the
Hantavirus: The virus causative agent of Hantavirus cardiopulmonary syndrome. A zoontic disease with a reservoi
Hantavirus Cardiopulmonary Syndrome: A deadly disease transmitted to humans by infected rodents through urine, droppings, or saliva. Huma
Hazard: A source of potential harm from past, current, or future exposures.
Hazardous Substance Release And Health Effects Database (Hazdat): The scientific and administrative database system developed by ATSDR to manage data collection, retr
Hazardous Waste: Potentially harmful substances that have been released or discarded into the environment.
Health Consultation: A review of available information or collection of new data to respond to a specific health question
Health Education: Programs designed with a community to help it know about health risks and how to reduce these risks.
Health Investigation: The collection and evaluation of information about the health of community residents. This informati
Health Promotion: The process of enabling people to increase control over, and to improve, their health.
Health Statistics Review: The analysis of existing health information (i.e., from death certificates, birth defects registries
Hectic Fever: A daily recurring fever with profound sweating, chills, and flushed appearance-- often associated wi
Hemagglutinin: One of the enzymes found on the surface of the Influenza virus. It is responsible for binding the vi
Hemorrhagic Fever: The viral hemorrhagic fevers (VHFs) are a diverse group of animal and human illnesses that are cause
Herd Immunity: A type of community protection from disease that occurs when the vaccination of a portion of the pop
Highly Active Anti-Retroviral Therapy (HAART): A treatment to combat AIDS using several different antiretroviral drugs at the same time.
Hives: A skin eruption of smooth, slightly elevated areas on the skin which is redder or paler than the sur
Horizontal Transmission: Transmission of an infection between members of the same species that are not in a parent-child rela
Hospital Acquired Infection: Nosocomial infections are infections which are a result of treatment in a hospital or a healthcare s
Human Immunodeficiency Virus (HIV): The causative agent of AIDS. There are two main strains known as HIV-1 and HIV-2, and a large number
Human Papillomavirus (HPV): A diverse group of viruses that infect the skin and mucous membranes of humans and a variety of anim
Iatrogenic: Disease (often infection) caused as a result of medical procedures such as surgery, catheterization
Immunity: Having sufficient biological defenses to avoid a specific disease.
Immunization: The process of rendering an individual protected (immune) against a certain disease. Vaccination is
Immunocompromised: Individuals whose immune system is weakened by any of a number of factors including disease (eg AIDS
In Vitro: In an artificial environment outside a living organism or body. For example, some toxicity testing i
In Vivo: Within a living organism or body. For example, some toxicity testing is done on whole animals, such
Inanition: Exhaustion from lack of nourishment; starvation.
Incidence: The number of new cases of a disease occurring in a given population over a certain period of time.
Incidence: The number of new cases of disease in a defined population over a specific time period [contrast wit
Incubation Period: The incubation period is the amount of time between infection with a virus or bacteria to the start
Indeterminate Public Health Hazard: The category used in ATSDR's public health assessment documents when a professional judgment about t
Index Case: The index case is the first disease case in an epidemic. Sometimes called "patient zero’.
Infected Category: Individuals in the SIR model who are infected by the disease and are capable of infecting other indi
Infection: In the early part of the last century, infections were thought to be the propagation of disease by e
Inflammation: Redness, swelling, pain, tenderness, heat, and disturbed function of an area of the body. In the las
Ingestion: The act of swallowing something through eating, drinking, or mouthing objects. A hazardous substance
Inhalation: The act of breathing. A hazardous substance can enter the body this way [see route of exposure].
Intermediate Duration Exposure: Contact with a substance that occurs for more than 14 days and less than a year [compare with acute
Intermittent Epidemic: An intermittent epidemic occurs when a group of people is exposed to a single common source of infec
Jaundice: Yellow discoloration of the skin, whites of the eyes, and mucous membranes, due to an increase of bi
Kings Evil: A popular name for scrofula. The name originated in the time of Edward the Confessor, with the belie
Kochâ€™s Postulates: Four criteria proposed by Robert Koch and designed to establish a causal relationship between a caus
Lockjaw: Tetanus, a disease in which the jaws become firmly locked together
Lowest-Observed-Adverse-Effect Level (LOAEL): The lowest tested dose of a substance that has been reported to cause harmful (adverse) health effec
Lyme Disease: A zoonotic disease vectored by ticks. Small mammals are the main reservoir species.
Malaria: A disease caused by a number of species of the protozoan Plasmodium. It is vectored by mosquitoes, w
Marasmus: Malnutrition occurring in infants and young children, caused by an insufficient intake of calories o
Marburg Virus: The causative agent of Marburg haemorrhagic fever. The virus is closely related to Ebola and origina
MDR-TB: Multi-drug resistant Tuberculosis – any strain of TB that is resistant to both of the two main fir
Measles: A viral disease of humans easily transmitted via the respiratory route. Prior to the introduction of
Medical Monitoring: A set of medical tests and physical exams specifically designed to evaluate whether an individual's
Meningitis: Inflammation of the meninges characterized by high fever, severe headache, and stiff neck or back mu
Merozoite: A stage in the life cycle of the Plasmodium parasite, causative agent of malaria. Initially produce
Metabolism: The conversion or breakdown of a substance from one form to another by a living organism.
Miasma Theory: The theory that diseases were caused by miasma or bad air arising from organic decay, filth, or othe
Milk Sick: poisoning resulting from the drinking of milk produced by a cow who had eaten a plant known as white
Minimal Risk Level (MRL): An ATSDR estimate of daily human exposure to a hazardous substance at or below which that substance
Mixed Epidemiuc: A mixed epidemic occurs when a group of people is exposed when a group of people is exposed to a sin
MMR Vaccine: A mixture of live but attenuated viruses, administered for immunization against measles, mumps and r
Morbidity: State of being ill or diseased. Morbidity is the occurrence of a disease or condition that alters he
Mortality: Death. The morbidity and mortality rates for a disease convey two different, and important, pieces o
MRSA: Methicillin-resistant Staphylococcus aureus (MRSA). It has evolved an ability to survive treatment w
Mumps: A viral disease of humans. Prior to the introduction of a vaccine, it was a common childhood disease
Mutagen: A substance that causes mutations (genetic damage).
Mutant Swarm: (aka viral swarm) A group of viruses of the same species but with slightly different genetic sequenc
Mutation: A change (damage) to the DNA, genes, or chromosomes of living organisms.
Mutation Rate: The chance of a mutation occurring in an organism or gene in each cell division.
Mycobacterium Bovis: The slow-growing bacterium that is the causative agent of tuberculosis in cattle (known as bovine TB
Mycobacterium Tuberculosis: The slow-growing bacterium that is the causative agent of tuberculosis in humans.
National Priorities List For Uncontrolled Hazardous Waste Sites: (National Priorities List or NPL) EPA's list of the most serious uncontrolled or abandoned hazardous
National Toxicology Program (NTP): Part of the Department of Health and Human Services. NTP develops and carries out tests to predict w
Neuralgia: Sharp and paroxysmal pain along the course of a sensory nerve.
Neuraminidase: One of the enzymes found on the surface of the Influenza virus. It promotes the release of progeny v
No Public Health Hazard: A category used in ATSDR's public health assessment documents for sites where people have never and
No-Observed-Adverse-Effect Level (NOAEL): The highest tested dose of a substance that has been reported to have no harmful (adverse) health ef
Outbreak: The appearance of several cases of a disease in an area previously experiencing no, or very few, cas
Pandemic: A worldwide epidemic affecting an exceptionally high proportion of the global population.
Pathogen: A biological agent that causes disease or illness to its host.
Peptidoglycan: Peptidoglycan is a polymer consisting of sugars and amino acids that forms a mesh-like layer outsid
Phylogeny: The evolutionary history of a taxonomic group.
Physiologically Based Pharmacokinetic Model (PBPK Model): A computer model that describes what happens to a chemical in the body. This model describes how the
Pica: A craving to eat nonfood items, such as dirt, paint chips, and clay. Some children exhibit pica-rela
Plague Of Justinian: (541-542) The Plague of Justinian was a pandemic that afflicted the Byzantine Empire, including its
Plasmid: DNA separate from the chromosomal DNA and capable of independent replication. Found naturally in man
Plasmodium Falciparum: The main causative agent of malaria in man. Although other Plasmodium species can cause the disease
Pleurisy: Inflammation of the pleura, the lining of the chest cavity. Symptoms are chills, fever, dry cough, a
Plume: A volume of a substance that moves from its source to places farther away from the source. Plumes ca
Pneumonic Plague: A generally fatal form of bubonic plague in which the infecting organisms infect the lungs. In contr
Point Of Exposure: The place where someone can come into contact with a substance present in the environment [see expos
Point Source Epidemic: A point source epidemic occurs when a group of people is exposed to a single common source of infect
Polio: Poliomyelitis, often called polio or infantile paralysis, is an acute viral infectious disease of hu
Population: A group or number of people living within a specified area or sharing similar characteristics (such
Potentially Responsible Party (PRP): A company, government, or person legally responsible for cleaning up the pollution at a hazardous wa
Prevalence: The number of instances of a given disease or other condition in a given population at a designated
Prevalence Survey: The measure of the current level of disease(s) or symptoms and exposures through a questionnaire tha
Prevention: Actions that reduce exposure or other risks, keep people from getting sick, or keep disease from get
Prokarytote: An organism lacking a true nucleus, such as a bacteria (cf eukaryote)
Propagated Epidemic: A propagated epidemic occurs when an infection is spread from person to person (either directly or v
Protozoa: Single-celled eukaryotic organisms
Public Availability Session: An informal, drop-by meeting at which community members can meet one-on-one with ATSDR staff members
Public Comment Period: An opportunity for the public to comment on agency findings or proposed activities contained in draf
Public Health Advisory: A statement made by ATSDR to EPA or a state regulatory agency that a release of hazardous substances
Public Health Assessment (PHA): An ATSDR document that examines hazardous substances, health outcomes, and community concerns at a h
Public Health Hazard: A category used in ATSDR's public health assessments for sites that pose a public health hazard beca
Public Health Hazard Categories: Public health hazard categories are statements about whether people could be harmed by conditions pr
Public Health Statement: The first chapter of an ATSDR toxicological profile. The public health statement is a summary writte
Public Health Surveillance: The ongoing, systematic collection, analysis, and interpretation of health data. This activity also
Public Meeting: A public forum with community members for communication about a site.
Quinsy: An acute inflammation of the tonsils, often leading to an abscess
R-Plasmid: A plasmid carrying genes controlling resistance to various drugs.
Radioisotope: An unstable or radioactive isotope (form) of an element that can change into another element by givi
Radionuclide: Any radioactive isotope (form) of any element.
Reassortment: A mixing of the genetic material of two similar viruses that are infecting the same cell.
Receptor Population: People who could come into contact with hazardous substances [see exposure pathway].
Recovered Or Removed Category: Individuals in the SIR model who were infected by the disease but are no longer infectious by virtue
Reference Dose (Rfd): An EPA estimate, with uncertainty or safety factors built in, of the daily lifetime dose of a substa
Registry: A systematic collection of information on persons exposed to a specific substance or having specific
Relative Risk: Relative risk is a ratio of the probability of the event occurring in the exposed group versus non-e
Remedial Investigation: The CERCLA process of determining the type and extent of hazardous material contamination at a site.
Reservoir: (or Natural Reservoir)The long-term host of the pathogen of an infectious disease. The long term hos
Residual Spraying: The application of small amounts of insecticide to the interior walls of houses to kill and repel ma
Resource Conservation And Recovery Act (RCRA): (1976, 1984) This Act regulates management and disposal of hazardous wastes currently generated, tre
Retrovirus: A type of RNA virus (such as HIV ) that reproduces by transcribing itself into DNA (using reverse tr
Reverse Transcriptase: An enzyme that is unique to all retroviruses. It reads the genetic information of the retrovirus, wh
RFA: RCRA Facility Assessment. An assessment required by RCRA to identify potential and actual releases o
Risk: The probability that something will cause injury or harm.
Risk Communication: The exchange of information to increase understanding of health risks.
Risk Reduction: Actions that can decrease the likelihood that individuals, groups, or communities will experience di
RNA Virus: A virus that has ribonucleic acid (RNA) as its genetic material and does not replicate using a DNA i
Route Of Exposure: The way people come into contact with a hazardous substance. Three routes of exposure are breathing
Rubella: (German measles) A mild viral diseaseof humans transmitted via the respiratory route. Although child
Sample: A portion or piece of a whole. A selected subset of a population or subset of whatever is being stud
Sample Size: The number of units chosen from a population or an environment.
Scrofula: Primary tuberculosis of the lymphatic glands, especially those in the neck. A disease of children an
Septic: Infected, a condition of local or generalized invasion of the body by disease-causing germs.
Septicimic Plague: A generally fatal form of bubonic plague in which infecting organisms invade the bloodstream.
Simian Immunodeficiency Virus (SIV): A virus that is found, in numerous strains, in primates.
SIR Model: A simple model of disease dynamics that tracks the population as it enters and leaves three categori
Solvent: A liquid capable of dissolving or dispersing another substance (for example, acetone or mineral spir
Source Of Contamination: The place where a hazardous substance comes from, such as a landfill, waste pond, incinerator, stora
Special Populations: People who might be more sensitive or susceptible to exposure to hazardous substances because of fac
Species Richness: The number of species present within a community.
Spill-Back: The transmission of infectious agents from wildlife populations back to domestic population.
Spill-Over: The transmission of infectious agents from reservoir domestic populations to wildlife populations.
Sporozoite: A stage in the life cycle of the Plasmodium parasite, causative agent of malaria. Found in the sali
Stakeholder: A person, group, or community who has an interest in activities at a hazardous waste site.
Staphylococcus Aureus: A spherical bacterium, frequently living on the skin or in the nose of a person, and the most common
Statistics: A branch of mathematics that deals with collecting, reviewing, summarizing, and interpreting data or
Substance-Specific Applied Research: A program of research designed to fill important data needs for specific hazardous substances identi
Superfund Amendments And Reauthorization Act (SARA): In 1986, SARA amended the Comprehensive Environmental Response, Compensation, and Liability Act of 1
Superspreader: Individuals who are responsible for a high proportion of the infections within a population.
Surface Water: Water on the surface of the earth, such as in lakes, rivers, streams, ponds, and springs [compare wi
Survey: A systematic collection of information or data. A survey can be conducted to collect information fro
Susceptible Category: Individuals in the SIR model who are uninfected by the disease and are capable of becoming infected.
Synergistic Effect: A biologic response to multiple substances where one substance worsens the effect of another substan
Teething: The entire process which results in the eruption of the teeth. Nineteenth-century medical reports st
Teratogen: A substance that causes defects in development between conception and birth. A teratogen is a substa
Tetanus: An infectious, often-fatal disease caused by a specific bacterium that enters the body through wound
Third Cholera Pandemic: (1852-1860) Included outbreaks in London. The Broad Street outbreak investigated by John Snow was pa
Thrush: A disease characterized by whitish spots and ulcers on the membranes of the mouth, tongue, and fauce
Toxic Agent: Chemical or physical (for example, radiation, heat, cold, microwaves) agents that, under certain cir
Toxicological Profile: An ATSDR document that examines, summarizes, and interprets information about a hazardous substance
Toxicology: The study of the harmful effects of substances on humans or animals.
Transduction: The process by which bacterial DNA is moved from one bacterium to another by a virus.
Transformation: The genetic alteration of a cell resulting from the uptake and expression of foreign genetic materia
Trismus Nascentium Or Neonatorum: A form of tetanus seen only in infants, almost invariably in the first five days of life.
Tuberculosis: A chronic infectious disease usually caused by Mycobacterium tuberculosis in humans.
Tumor: An abnormal mass of tissue that results from excessive cell division that is uncontrolled and progre
Typhoid Fever: An infectious, often-fatal disease, usually occurring in the summer months--characterized by intesti
Typhus: An acute, infectious disease transmitted by lice and fleas. The epidemic or classic form is louse bo
Uncertainty Factor: Mathematical adjustments for reasons of safety when knowledge is incomplete. For example, factors us
Urgent Public Health Hazard: A category used in ATSDR's public health assessments for sites where short-term exposures (less than
Vaccination: Administering weakened or dead pathogens to a healthy person or animal, with the intent of conferrin
Vaccine: A preparation of killed microorganisms, living attenuated organisms, or living fully virulent organi
Vancomycin: An antibiotic used in the treatment of infections caused by Gram-positive bacteria. It has tradition
Variant Creutzfeldt-Jakob Disease (vCJD): An infectious disease that affects the brain and nervous system in humans. The infectious agent in
Vector: A living organism that transmits the infectious agent eg. Ticks, fleas and mosquitoes.
Vertical Transmission: Transmission of an infection, such as HIV, from mother to child during the perinatal period, the per
Vibrio Cholera: The bacterial causative agent of cholera in humans.
Viral Swarm: (aka mutant swarm) A group of viruses of the same species but with slightly different genetic sequen
Virulence: From the Latin word virulentus, which means 'full of poison.' The relative ability of a microbe to c
Virus: A sub-microscopic infectious agent that is unable to grow or reproduce outside of a host cell. Each
Volatile Organic Compounds (VOCS): Organic compounds that evaporate readily into the air. VOCs include substances such as benzene, tolu
VRSA: Vancomycin-resistant Staphylococcus aureus (VRSA) is a strain of Staphylococcus aureus that has beco
XDR-TB: Extreme drug resistant TB – any strain of TB that is resistant to both of the two main first line
Yellow Fever: An acute, often-fatal, infectiousdisease of warm climates--caused by a virus transmitted by mosquito
Yersinia Pestis: The bacterial causative agent of Bubonic Plague. Named in honor of the discoverer Alexandre Yersin a
Zoonoses: Diseases which occur primarily in animals but may occasionally be transmitted to people eg. Lyme dis