Geography: The science dealing with the earth and its life, especially the description of land, sea, and air and the distribution of plant and animal life, including humanity and human industries with reference to the mutual relations of these elements. (From Webster, 3d ed)Geographic Locations: The continents and countries situated on those continents; the UNITED STATES and each of the constituent states arranged by region; CANADA and each of its provinces; AUSTRALIA and each of its states; the major bodies of water and major islands on both hemispheres; and selected major cities.Historical Geographic Locations: Countries known in remote history (as BYZANTIUM) or former names of countries reflecting political changes in the 19th or 20th century (as GERMANY, EAST).Phylogeny: The relationships of groups of organisms as reflected by their genetic makeup.Genetic Variation: Genotypic differences observed among individuals in a population.Sequence Analysis, DNA: A multistage process that includes cloning, physical mapping, subcloning, determination of the DNA SEQUENCE, and information analysis.Phylogeography: A field of study concerned with the principles and processes governing the geographic distributions of genealogical lineages, especially those within and among closely related species. (Avise, J.C., Phylogeography: The History and Formation of Species. Harvard University Press, 2000)Cluster Analysis: A set of statistical methods used to group variables or observations into strongly inter-related subgroups. In epidemiology, it may be used to analyze a closely grouped series of events or cases of disease or other health-related phenomenon with well-defined distribution patterns in relation to time or place or both.Molecular Sequence Data: Descriptions of specific amino acid, carbohydrate, or nucleotide sequences which have appeared in the published literature and/or are deposited in and maintained by databanks such as GENBANK, European Molecular Biology Laboratory (EMBL), National Biomedical Research Foundation (NBRF), or other sequence repositories.United StatesGeographic Information Systems: Computer systems capable of assembling, storing, manipulating, and displaying geographically referenced information, i.e. data identified according to their locations.DNA, Bacterial: Deoxyribonucleic acid that makes up the genetic material of bacteria.Geography, Medical: The area of medicine concerned with the effects on health and disease due to geographic factors such as CLIMATE, environmental conditions, and geographic location.Americas: The general name for NORTH AMERICA; CENTRAL AMERICA; and SOUTH AMERICA unspecified or combined.Tamaricaceae: A plant family of the order Violales, subclass Dilleniidae, class Magnoliopsida.Bacterial Typing Techniques: Procedures for identifying types and strains of bacteria. The most frequently employed typing systems are BACTERIOPHAGE TYPING and SEROTYPING as well as bacteriocin typing and biotyping.Professional Practice Location: Geographic area in which a professional person practices; includes primarily physicians and dentists.Genotype: The genetic constitution of the individual, comprising the ALLELES present at each GENETIC LOCUS.Polymerase Chain Reaction: In vitro method for producing large amounts of specific DNA or RNA fragments of defined length and sequence from small amounts of short oligonucleotide flanking sequences (primers). The essential steps include thermal denaturation of the double-stranded target molecules, annealing of the primers to their complementary sequences, and extension of the annealed primers by enzymatic synthesis with DNA polymerase. The reaction is efficient, specific, and extremely sensitive. Uses for the reaction include disease diagnosis, detection of difficult-to-isolate pathogens, mutation analysis, genetic testing, DNA sequencing, and analyzing evolutionary relationships.DNA Fingerprinting: A technique for identifying individuals of a species that is based on the uniqueness of their DNA sequence. Uniqueness is determined by identifying which combination of allelic variations occur in the individual at a statistically relevant number of different loci. In forensic studies, RESTRICTION FRAGMENT LENGTH POLYMORPHISM of multiple, highly polymorphic VNTR LOCI or MICROSATELLITE REPEAT loci are analyzed. The number of loci used for the profile depends on the ALLELE FREQUENCY in the population.Asia: The largest of the continents. It was known to the Romans more specifically as what we know today as Asia Minor. The name comes from at least two possible sources: from the Assyrian asu (to rise) or from the Sanskrit usa (dawn), both with reference to its being the land of the rising sun, i.e., eastern as opposed to Europe, to the west. (From Webster's New Geographical Dictionary, 1988, p82 & Room, Brewer's Dictionary of Names, 1992, p34)Cyprus: An island republic in the eastern Mediterranean Sea. Its capital is Nicosia. It was colonized by the Phoenicians and ancient Greeks and ruled successively by the Assyrian, Persian, Ptolemaic, Roman, and Byzantine Empires. It was under various countries from the 12th to the 20th century but became independent in 1960. The name comes from the Greek Kupros, probably representing the Sumerian kabar or gabar, copper, famous in historic times for its copper mines. The cypress tree is also named after the island. (From Webster's New Geographical Dictionary, 1988, p308 & Room, Brewer's Dictionary of Names, 1992, p134)Species Specificity: The restriction of a characteristic behavior, anatomical structure or physical system, such as immune response; metabolic response, or gene or gene variant to the members of one species. It refers to that property which differentiates one species from another but it is also used for phylogenetic levels higher or lower than the species.Base Sequence: The sequence of PURINES and PYRIMIDINES in nucleic acids and polynucleotides. It is also called nucleotide sequence.Genetics, Population: The discipline studying genetic composition of populations and effects of factors such as GENETIC SELECTION, population size, MUTATION, migration, and GENETIC DRIFT on the frequencies of various GENOTYPES and PHENOTYPES using a variety of GENETIC TECHNIQUES.China: A country spanning from central Asia to the Pacific Ocean.Biodiversity: The variety of all native living organisms and their various forms and interrelationships.EuropeDemography: Statistical interpretation and description of a population with reference to distribution, composition, or structure.Seasons: Divisions of the year according to some regularly recurrent phenomena usually astronomical or climatic. (From McGraw-Hill Dictionary of Scientific and Technical Terms, 6th ed)Rural Population: The inhabitants of rural areas or of small towns classified as rural.RNA, Ribosomal, 16S: Constituent of 30S subunit prokaryotic ribosomes containing 1600 nucleotides and 21 proteins. 16S rRNA is involved in initiation of polypeptide synthesis.Polymorphism, Restriction Fragment Length: Variation occurring within a species in the presence or length of DNA fragment generated by a specific endonuclease at a specific site in the genome. Such variations are generated by mutations that create or abolish recognition sites for these enzymes or change the length of the fragment.IndiaMolecular Epidemiology: The application of molecular biology to the answering of epidemiological questions. The examination of patterns of changes in DNA to implicate particular carcinogens and the use of molecular markers to predict which individuals are at highest risk for a disease are common examples.Serotyping: Process of determining and distinguishing species of bacteria or viruses based on antigens they share.Urban Population: The inhabitants of a city or town, including metropolitan areas and suburban areas.Middle East: The region of southwest Asia and northeastern Africa usually considered as extending from Libya on the west to Afghanistan on the east. (From Webster's New Geographical Dictionary, 1988)Prevalence: The total number of cases of a given disease in a specified population at a designated time. It is differentiated from INCIDENCE, which refers to the number of new cases in the population at a given time.Residence Characteristics: Elements of residence that characterize a population. They are applicable in determining need for and utilization of health services.ChileDNA, Ribosomal: DNA sequences encoding RIBOSOMAL RNA and the segments of DNA separating the individual ribosomal RNA genes, referred to as RIBOSOMAL SPACER DNA.Climate: The longterm manifestations of WEATHER. (McGraw-Hill Dictionary of Scientific and Technical Terms, 6th ed)Electrophoresis, Gel, Pulsed-Field: Gel electrophoresis in which the direction of the electric field is changed periodically. This technique is similar to other electrophoretic methods normally used to separate double-stranded DNA molecules ranging in size up to tens of thousands of base-pairs. However, by alternating the electric field direction one is able to separate DNA molecules up to several million base-pairs in length.FloridaEvolution, Molecular: The process of cumulative change at the level of DNA; RNA; and PROTEINS, over successive generations.Australia: The smallest continent and an independent country, comprising six states and two territories. Its capital is Canberra.Censuses: Enumerations of populations usually recording identities of all persons in every place of residence with age or date of birth, sex, occupation, national origin, language, marital status, income, relation to head of household, information on the dwelling place, education, literacy, health-related data (e.g., permanent disability), etc. The census or "numbering of the people" is mentioned several times in the Old Testament. Among the Romans, censuses were intimately connected with the enumeration of troops before and after battle and probably a military necessity. (From Last, A Dictionary of Epidemiology, 3d ed; Garrison, An Introduction to the History of Medicine, 4th ed, p66, p119)Ethnic Groups: A group of people with a common cultural heritage that sets them apart from others in a variety of social relationships.North AmericaCanada: The largest country in North America, comprising 10 provinces and three territories. Its capital is Ottawa.Random Amplified Polymorphic DNA Technique: Technique that utilizes low-stringency polymerase chain reaction (PCR) amplification with single primers of arbitrary sequence to generate strain-specific arrays of anonymous DNA fragments. RAPD technique may be used to determine taxonomic identity, assess kinship relationships, analyze mixed genome samples, and create specific probes.Socioeconomic Factors: Social and economic factors that characterize the individual or group within the social structure.Risk Factors: An aspect of personal behavior or lifestyle, environmental exposure, or inborn or inherited characteristic, which, on the basis of epidemiologic evidence, is known to be associated with a health-related condition considered important to prevent.DNA, Ribosomal Spacer: The intergenic DNA segments that are between the ribosomal RNA genes (internal transcribed spacers) and between the tandemly repeated units of rDNA (external transcribed spacers and nontranscribed spacers).Health Services Accessibility: The degree to which individuals are inhibited or facilitated in their ability to gain entry to and to receive care and services from the health care system. Factors influencing this ability include geographic, architectural, transportational, and financial considerations, among others.Microsatellite Repeats: A variety of simple repeat sequences that are distributed throughout the GENOME. They are characterized by a short repeat unit of 2-8 basepairs that is repeated up to 100 times. They are also known as short tandem repeats (STRs).AfricaEcosystem: A functional system which includes the organisms of a natural community together with their environment. (McGraw Hill Dictionary of Scientific and Technical Terms, 4th ed)World Health: The concept pertaining to the health status of inhabitants of the world.British Columbia: A province of Canada on the Pacific coast. Its capital is Victoria. The name given in 1858 derives from the Columbia River which was named by the American captain Robert Gray for his ship Columbia which in turn was named for Columbus. (From Webster's New Geographical Dictionary, 1988, p178 & Room, Brewer's Dictionary of Names, 1992, p81-2)New Zealand: A group of islands in the southwest Pacific. Its capital is Wellington. It was discovered by the Dutch explorer Abel Tasman in 1642 and circumnavigated by Cook in 1769. Colonized in 1840 by the New Zealand Company, it became a British crown colony in 1840 until 1907 when colonial status was terminated. New Zealand is a partly anglicized form of the original Dutch name Nieuw Zeeland, new sea land, possibly with reference to the Dutch province of Zeeland. (From Webster's New Geographical Dictionary, 1988, p842 & Room, Brewer's Dictionary of Names, 1992, p378)DNA, Mitochondrial: Double-stranded DNA of MITOCHONDRIA. In eukaryotes, the mitochondrial GENOME is circular and codes for ribosomal RNAs, transfer RNAs, and about 10 proteins.Genes, Bacterial: The functional hereditary units of BACTERIA.Time Factors: Elements of limited time intervals, contributing to particular results or situations.IsraelAge Factors: Age as a constituent element or influence contributing to the production of a result. It may be applicable to the cause or the effect of a circumstance. It is used with human or animal concepts but should be differentiated from AGING, a physiological process, and TIME FACTORS which refers only to the passage of time.Polymorphism, Genetic: The regular and simultaneous occurrence in a single interbreeding population of two or more discontinuous genotypes. The concept includes differences in genotypes ranging in size from a single nucleotide site (POLYMORPHISM, SINGLE NUCLEOTIDE) to large nucleotide sequences visible at a chromosomal level.Incidence: The number of new cases of a given disease during a given period in a specified population. It also is used for the rate at which new events occur in a defined population. It is differentiated from PREVALENCE, which refers to all cases, new or old, in the population at a given time.Amplified Fragment Length Polymorphism Analysis: The detection of RESTRICTION FRAGMENT LENGTH POLYMORPHISMS by selective PCR amplification of restriction fragments derived from genomic DNA followed by electrophoretic analysis of the amplified restriction fragments.Disease Outbreaks: Sudden increase in the incidence of a disease. The concept includes EPIDEMICS and PANDEMICS.South AmericaRural Health Services: Health services, public or private, in rural areas. The services include the promotion of health and the delivery of health care.Seawater: The salinated water of OCEANS AND SEAS that provides habitat for marine organisms.Emigration and Immigration: The process of leaving one's country to establish residence in a foreign country.Great BritainGenome, Viral: The complete genetic complement contained in a DNA or RNA molecule in a virus.Questionnaires: Predetermined sets of questions used to collect data - clinical data, social status, occupational group, etc. The term is often applied to a self-completed survey instrument.Alleles: Variant forms of the same gene, occupying the same locus on homologous CHROMOSOMES, and governing the variants in production of the same gene product.Water Microbiology: The presence of bacteria, viruses, and fungi in water. This term is not restricted to pathogenic organisms.CaliforniaBacteria: One of the three domains of life (the others being Eukarya and ARCHAEA), also called Eubacteria. They are unicellular prokaryotic microorganisms which generally possess rigid cell walls, multiply by cell division, and exhibit three principal forms: round or coccal, rodlike or bacillary, and spiral or spirochetal. Bacteria can be classified by their response to OXYGEN: aerobic, anaerobic, or facultatively anaerobic; by the mode by which they obtain their energy: chemotrophy (via chemical reaction) or PHOTOTROPHY (via light reaction); for chemotrophs by their source of chemical energy: CHEMOLITHOTROPHY (from inorganic compounds) or chemoorganotrophy (from organic compounds); and by their source for CARBON; NITROGEN; etc.; HETEROTROPHY (from organic sources) or AUTOTROPHY (from CARBON DIOXIDE). They can also be classified by whether or not they stain (based on the structure of their CELL WALLS) with CRYSTAL VIOLET dye: gram-negative or gram-positive.Cross-Sectional Studies: Studies in which the presence or absence of disease or other health-related variables are determined in each member of the study population or in a representative sample at one particular time. This contrasts with LONGITUDINAL STUDIES which are followed over a period of time.Bacterial Proteins: Proteins found in any species of bacterium.Amino Acid Sequence: The order of amino acids as they occur in a polypeptide chain. This is referred to as the primary structure of proteins. It is of fundamental importance in determining PROTEIN CONFORMATION.DNA Primers: Short sequences (generally about 10 base pairs) of DNA that are complementary to sequences of messenger RNA and allow reverse transcriptases to start copying the adjacent sequences of mRNA. Primers are used extensively in genetic and molecular biology techniques.Gene Flow: The change in gene frequency in a population due to migration of gametes or individuals (ANIMAL MIGRATION) across population barriers. In contrast, in GENETIC DRIFT the cause of gene frequency changes are not a result of population or gamete movement.Feces: Excrement from the INTESTINES, containing unabsorbed solids, waste products, secretions, and BACTERIA of the DIGESTIVE SYSTEM.ScotlandHaplotypes: The genetic constitution of individuals with respect to one member of a pair of allelic genes, or sets of genes that are closely linked and tend to be inherited together such as those of the MAJOR HISTOCOMPATIBILITY COMPLEX.Plant Diseases: Diseases of plants.Multilocus Sequence Typing: Direct nucleotide sequencing of gene fragments from multiple housekeeping genes for the purpose of phylogenetic analysis, organism identification, and typing of species, strain, serovar, or other distinguishable phylogenetic level.Genes, rRNA: Genes, found in both prokaryotes and eukaryotes, which are transcribed to produce the RNA which is incorporated into RIBOSOMES. Prokaryotic rRNA genes are usually found in OPERONS dispersed throughout the GENOME, whereas eukaryotic rRNA genes are clustered, multicistronic transcriptional units.Disease Reservoirs: Animate or inanimate sources which normally harbor disease-causing organisms and thus serve as potential sources of disease outbreaks. Reservoirs are distinguished from vectors (DISEASE VECTORS) and carriers, which are agents of disease transmission rather than continuing sources of potential disease outbreaks.Anti-Bacterial Agents: Substances that reduce the growth or reproduction of BACTERIA.Databases, Factual: Extensive collections, reputedly complete, of facts and data garnered from material of a specialized subject area and made available for analysis and application. The collection can be automated by various contemporary methods for retrieval. The concept should be differentiated from DATABASES, BIBLIOGRAPHIC which is restricted to collections of bibliographic references.Bayes Theorem: A theorem in probability theory named for Thomas Bayes (1702-1761). In epidemiology, it is used to obtain the probability of disease in a group of people with some characteristic on the basis of the overall rate of that disease and of the likelihood of that characteristic in healthy and diseased individuals. The most familiar application is in clinical decision analysis where it is used for estimating the probability of a particular diagnosis given the appearance of some symptoms or test result.Population Dynamics: The pattern of any process, or the interrelationship of phenomena, which affects growth or change within a population.Cattle: Domesticated bovine animals of the genus Bos, usually kept on a farm or ranch and used for the production of meat or dairy products or for heavy labor.Regression Analysis: Procedures for finding the mathematical function which best describes the relationship between a dependent variable and one or more independent variables. In linear regression (see LINEAR MODELS) the relationship is constrained to be a straight line and LEAST-SQUARES ANALYSIS is used to determine the best fit. In logistic regression (see LOGISTIC MODELS) the dependent variable is qualitative rather than continuously variable and LIKELIHOOD FUNCTIONS are used to find the best relationship. In multiple regression, the dependent variable is considered to depend on more than a single independent variable.Soil Microbiology: The presence of bacteria, viruses, and fungi in the soil. This term is not restricted to pathogenic organisms.Population Surveillance: Ongoing scrutiny of a population (general population, study population, target population, etc.), generally using methods distinguished by their practicability, uniformity, and frequently their rapidity, rather than by complete accuracy.Age Distribution: The frequency of different ages or age groups in a given population. The distribution may refer to either how many or what proportion of the group. The population is usually patients with a specific disease but the concept is not restricted to humans and is not restricted to medicine.Sex Factors: Maleness or femaleness as a constituent element or influence contributing to the production of a result. It may be applicable to the cause or effect of a circumstance. It is used with human or animal concepts but should be differentiated from SEX CHARACTERISTICS, anatomical or physiological manifestations of sex, and from SEX DISTRIBUTION, the number of males and females in given circumstances.Infant, Newborn: An infant during the first month after birth.Indians, North American: Individual members of North American ethnic groups with ancient historic ancestral origins in Asia.Retrospective Studies: Studies used to test etiologic hypotheses in which inferences about an exposure to putative causal factors are derived from data relating to characteristics of persons under study or to events or experiences in their past. The essential feature is that some of the persons under study have the disease or outcome of interest and their characteristics are compared with those of unaffected persons.Birds: Warm-blooded VERTEBRATES possessing FEATHERS and belonging to the class Aves.Sequence Homology, Nucleic Acid: The sequential correspondence of nucleotides in one nucleic acid molecule with those of another nucleic acid molecule. Sequence homology is an indication of the genetic relatedness of different organisms and gene function.Nigeria: A republic in western Africa, south of NIGER between BENIN and CAMEROON. Its capital is Abuja.Environmental Monitoring: The monitoring of the level of toxins, chemical pollutants, microbial contaminants, or other harmful substances in the environment (soil, air, and water), workplace, or in the bodies of people and animals present in that environment.Seroepidemiologic Studies: EPIDEMIOLOGIC STUDIES based on the detection through serological testing of characteristic change in the serum level of specific ANTIBODIES. Latent subclinical infections and carrier states can thus be detected in addition to clinically overt cases.DNA, Fungal: Deoxyribonucleic acid that makes up the genetic material of fungi.Sequence Alignment: The arrangement of two or more amino acid or base sequences from an organism or organisms in such a way as to align areas of the sequences sharing common properties. The degree of relatedness or homology between the sequences is predicted computationally or statistically based on weights assigned to the elements aligned between the sequences. This in turn can serve as a potential indicator of the genetic relatedness between the organisms.Internet: A loose confederation of computer communication networks around the world. The networks that make up the Internet are connected through several backbone networks. The Internet grew out of the US Government ARPAnet project and was designed to facilitate information exchange.Environment: The external elements and conditions which surround, influence, and affect the life and development of an organism or population.MexicoBrazilFish Diseases: Diseases of freshwater, marine, hatchery or aquarium fish. This term includes diseases of both teleosts (true fish) and elasmobranchs (sharks, rays and skates).Symbiosis: The relationship between two different species of organisms that are interdependent; each gains benefits from the other or a relationship between different species where both of the organisms in question benefit from the presence of the other.Plasmids: Extrachromosomal, usually CIRCULAR DNA molecules that are self-replicating and transferable from one organism to another. They are found in a variety of bacterial, archaeal, fungal, algal, and plant species. They are used in GENETIC ENGINEERING as CLONING VECTORS.Genetic Markers: A phenotypically recognizable genetic trait which can be used to identify a genetic locus, a linkage group, or a recombination event.Nucleic Acid Hybridization: Widely used technique which exploits the ability of complementary sequences in single-stranded DNAs or RNAs to pair with each other to form a double helix. Hybridization can take place between two complimentary DNA sequences, between a single-stranded DNA and a complementary RNA, or between two RNA sequences. The technique is used to detect and isolate specific sequences, measure homology, or define other characteristics of one or both strands. (Kendrew, Encyclopedia of Molecular Biology, 1994, p503)Spain: Parliamentary democracy located between France on the northeast and Portugual on the west and bordered by the Atlantic Ocean and the Mediterranean Sea.Healthcare Disparities: Differences in access to or availability of medical facilities and services.Analysis of Variance: A statistical technique that isolates and assesses the contributions of categorical independent variables to variation in the mean of a continuous dependent variable.European Continental Ancestry Group: Individuals whose ancestral origins are in the continent of Europe.Swine: Any of various animals that constitute the family Suidae and comprise stout-bodied, short-legged omnivorous mammals with thick skin, usually covered with coarse bristles, a rather long mobile snout, and small tail. Included are the genera Babyrousa, Phacochoerus (wart hogs), and Sus, the latter containing the domestic pig (see SUS SCROFA).Microbial Sensitivity Tests: Any tests that demonstrate the relative efficacy of different chemotherapeutic agents against specific microorganisms (i.e., bacteria, fungi, viruses).Virulence Factors: Those components of an organism that determine its capacity to cause disease but are not required for its viability per se. Two classes have been characterized: TOXINS, BIOLOGICAL and surface adhesion molecules that effect the ability of the microorganism to invade and colonize a host. (From Davis et al., Microbiology, 4th ed. p486)Logistic Models: Statistical models which describe the relationship between a qualitative dependent variable (that is, one which can take only certain discrete values, such as the presence or absence of a disease) and an independent variable. A common application is in epidemiology for estimating an individual's risk (probability of a disease) as a function of a given risk factor.DNA Transposable Elements: Discrete segments of DNA which can excise and reintegrate to another site in the genome. Most are inactive, i.e., have not been found to exist outside the integrated state. DNA transposable elements include bacterial IS (insertion sequence) elements, Tn elements, the maize controlling elements Ac and Ds, Drosophila P, gypsy, and pogo elements, the human Tigger elements and the Tc and mariner elements which are found throughout the animal kingdom.Data Collection: Systematic gathering of data for a particular purpose from various sources, including questionnaires, interviews, observation, existing records, and electronic devices. The process is usually preliminary to statistical analysis of the data.Genome, Bacterial: The genetic complement of a BACTERIA as represented in its DNA.Ontario: A province of Canada lying between the provinces of Manitoba and Quebec. Its capital is Toronto. It takes its name from Lake Ontario which is said to represent the Iroquois oniatariio, beautiful lake. (From Webster's New Geographical Dictionary, 1988, p892 & Room, Brewer's Dictionary of Names, 1992, p391)DNA, Viral: Deoxyribonucleic acid that makes up the genetic material of viruses.Hospitals: Institutions with an organized medical staff which provide medical care to patients.Drug Resistance, Microbial: The ability of microorganisms, especially bacteria, to resist or to become tolerant to chemotherapeutic agents, antimicrobial agents, or antibiotics. This resistance may be acquired through gene mutation or foreign DNA in transmissible plasmids (R FACTORS).Continental Population Groups: Groups of individuals whose putative ancestry is from native continental populations based on similarities in physical appearance.Polymorphism, Single Nucleotide: A single nucleotide variation in a genetic sequence that occurs at appreciable frequency in the population.Physician's Practice Patterns: Patterns of practice related to diagnosis and treatment as especially influenced by cost of the service requested and provided.Phenotype: The outward appearance of the individual. It is the product of interactions between genes, and between the GENOTYPE and the environment.Biological Evolution: The process of cumulative change over successive generations through which organisms acquire their distinguishing morphological and physiological characteristics.Multivariate Analysis: A set of techniques used when variation in several variables has to be studied simultaneously. In statistics, multivariate analysis is interpreted as any analytic method that allows simultaneous study of two or more dependent variables.Cloning, Molecular: The insertion of recombinant DNA molecules from prokaryotic and/or eukaryotic sources into a replicating vehicle, such as a plasmid or virus vector, and the introduction of the resultant hybrid molecules into recipient cells without altering the viability of those cells.Mutation: Any detectable and heritable change in the genetic material that causes a change in the GENOTYPE and which is transmitted to daughter cells and to succeeding generations.Gene Frequency: The proportion of one particular in the total of all ALLELES for one genetic locus in a breeding POPULATION.Selection, Genetic: Differential and non-random reproduction of different genotypes, operating to alter the gene frequencies within a population.Health Care Surveys: Statistical measures of utilization and other aspects of the provision of health care services including hospitalization and ambulatory care.JapanReproducibility of Results: The statistical reproducibility of measurements (often in a clinical context), including the testing of instrumentation or techniques to obtain reproducible results. The concept includes reproducibility of physiological measurements, which may be used to develop rules to assess probability or prognosis, or response to a stimulus; reproducibility of occurrence of a condition; and reproducibility of experimental results.Antigens, Bacterial: Substances elaborated by bacteria that have antigenic activity.Sensitivity and Specificity: Binary classification measures to assess test results. Sensitivity or recall rate is the proportion of true positives. Specificity is the probability of correctly determining the absence of a condition. (From Last, Dictionary of Epidemiology, 2d ed)Algorithms: A procedure consisting of a sequence of algebraic formulas and/or logical steps to calculate or determine a given task.Likelihood Functions: Functions constructed from a statistical model and a set of observed data which give the probability of that data for various values of the unknown model parameters. Those parameter values that maximize the probability are the maximum likelihood estimates of the parameters.Escherichia coli: A species of gram-negative, facultatively anaerobic, rod-shaped bacteria (GRAM-NEGATIVE FACULTATIVELY ANAEROBIC RODS) commonly found in the lower part of the intestine of warm-blooded animals. It is usually nonpathogenic, but some strains are known to produce DIARRHEA and pyogenic infections. Pathogenic strains (virotypes) are classified by their specific pathogenic mechanisms such as toxins (ENTEROTOXIGENIC ESCHERICHIA COLI), etc.Models, Statistical: Statistical formulations or analyses which, when applied to data and found to fit the data, are then used to verify the assumptions and parameters used in the analysis. Examples of statistical models are the linear model, binomial model, polynomial model, two-parameter model, etc.Blotting, Southern: A method (first developed by E.M. Southern) for detection of DNA that has been electrophoretically separated and immobilized by blotting on nitrocellulose or other type of paper or nylon membrane followed by hybridization with labeled NUCLEIC ACID PROBES.HIV Infections: Includes the spectrum of human immunodeficiency virus infections that range from asymptomatic seropositivity, thru AIDS-related complex (ARC), to acquired immunodeficiency syndrome (AIDS).TaiwanEnvironmental Exposure: The exposure to potentially harmful chemical, physical, or biological agents in the environment or to environmental factors that may include ionizing radiation, pathogenic organisms, or toxic chemicals.Models, Theoretical: Theoretical representations that simulate the behavior or activity of systems, processes, or phenomena. They include the use of mathematical equations, computers, and other electronic equipment.Sex Distribution: The number of males and females in a given population. The distribution may refer to how many men or women or what proportion of either in the group. The population is usually patients with a specific disease but the concept is not restricted to humans and is not restricted to medicine.Virulence: The degree of pathogenicity within a group or species of microorganisms or viruses as indicated by case fatality rates and/or the ability of the organism to invade the tissues of the host. The pathogenic capacity of an organism is determined by its VIRULENCE FACTORS.Malaria: A protozoan disease caused in humans by four species of the PLASMODIUM genus: PLASMODIUM FALCIPARUM; PLASMODIUM VIVAX; PLASMODIUM OVALE; and PLASMODIUM MALARIAE; and transmitted by the bite of an infected female mosquito of the genus ANOPHELES. Malaria is endemic in parts of Asia, Africa, Central and South America, Oceania, and certain Caribbean islands. It is characterized by extreme exhaustion associated with paroxysms of high FEVER; SWEATING; shaking CHILLS; and ANEMIA. Malaria in ANIMALS is caused by other species of plasmodia.Cohort Studies: Studies in which subsets of a defined population are identified. These groups may or may not be exposed to factors hypothesized to influence the probability of the occurrence of a particular disease or other outcome. Cohorts are defined populations which, as a whole, are followed in an attempt to determine distinguishing subgroup characteristics.Case-Control Studies: Studies which start with the identification of persons with a disease of interest and a control (comparison, referent) group without the disease. The relationship of an attribute to the disease is examined by comparing diseased and non-diseased persons with regard to the frequency or levels of the attribute in each group.Risk Assessment: The qualitative or quantitative estimation of the likelihood of adverse effects that may result from exposure to specified health hazards or from the absence of beneficial influences. (Last, Dictionary of Epidemiology, 1988)RNA, Viral: Ribonucleic acid that makes up the genetic material of viruses.Interviews as Topic: Conversations with an individual or individuals held in order to obtain information about their background and other personal biographical data, their attitudes and opinions, etc. It includes school admission or job interviews.Helicobacter pylori: A spiral bacterium active as a human gastric pathogen. It is a gram-negative, urease-positive, curved or slightly spiral organism initially isolated in 1982 from patients with lesions of gastritis or peptic ulcers in Western Australia. Helicobacter pylori was originally classified in the genus CAMPYLOBACTER, but RNA sequencing, cellular fatty acid profiles, growth patterns, and other taxonomic characteristics indicate that the micro-organism should be included in the genus HELICOBACTER. It has been officially transferred to Helicobacter gen. nov. (see Int J Syst Bacteriol 1989 Oct;39(4):297-405).Odds Ratio: The ratio of two odds. The exposure-odds ratio for case control data is the ratio of the odds in favor of exposure among cases to the odds in favor of exposure among noncases. The disease-odds ratio for a cohort or cross section is the ratio of the odds in favor of disease among the exposed to the odds in favor of disease among the unexposed. The prevalence-odds ratio refers to an odds ratio derived cross-sectionally from studies of prevalent cases.EnglandModels, Genetic: Theoretical representations that simulate the behavior or activity of genetic processes or phenomena. They include the use of mathematical equations, computers, and other electronic equipment.Risk: The probability that an event will occur. It encompasses a variety of measures of the probability of a generally unfavorable outcome.Treatment Outcome: Evaluation undertaken to assess the results or consequences of management and procedures used in combating disease in order to determine the efficacy, effectiveness, safety, and practicability of these interventions in individual cases or series.Helicobacter Infections: Infections with organisms of the genus HELICOBACTER, particularly, in humans, HELICOBACTER PYLORI. The clinical manifestations are focused in the stomach, usually the gastric mucosa and antrum, and the upper duodenum. This infection plays a major role in the pathogenesis of type B gastritis and peptic ulcer disease.Health Surveys: A systematic collection of factual data pertaining to health and disease in a human population within a given geographic area.Drug Resistance, Bacterial: The ability of bacteria to resist or to become tolerant to chemotherapeutic agents, antimicrobial agents, or antibiotics. This resistance may be acquired through gene mutation or foreign DNA in transmissible plasmids (R FACTORS).Attitude of Health Personnel: Attitudes of personnel toward their patients, other professionals, toward the medical care system, etc.Pregnancy: The status during which female mammals carry their developing young (EMBRYOS or FETUSES) in utero before birth, beginning from FERTILIZATION to BIRTH.Chromosome Mapping: Any method used for determining the location of and relative distances between genes on a chromosome.Neoplasms: New abnormal growth of tissue. Malignant neoplasms show a greater degree of anaplasia and have the properties of invasion and metastasis, compared to benign neoplasms.Hospitalization: The confinement of a patient in a hospital.Prospective Studies: Observation of a population for a sufficient number of persons over a sufficient number of years to generate incidence or mortality rates subsequent to the selection of the study group.Registries: The systems and processes involved in the establishment, support, management, and operation of registers, e.g., disease registers.Health Knowledge, Attitudes, Practice: Knowledge, attitudes, and associated behaviors which pertain to health-related topics such as PATHOLOGIC PROCESSES or diseases, their prevention, and treatment. This term refers to non-health workers and health workers (HEALTH PERSONNEL).Diet: Regular course of eating and drinking adopted by a person or animal.Follow-Up Studies: Studies in which individuals or populations are followed to assess the outcome of exposures, procedures, or effects of a characteristic, e.g., occurrence of disease.Photic Stimulation: Investigative technique commonly used during ELECTROENCEPHALOGRAPHY in which a series of bright light flashes or visual patterns are used to elicit brain activity.Cues: Signals for an action; that specific portion of a perceptual field or pattern of stimuli to which a subject has learned to respond.Magnetic Resonance Imaging: Non-invasive method of demonstrating internal anatomy based on the principle that atomic nuclei in a strong magnetic field absorb pulses of radiofrequency energy and emit them as radiowaves which can be reconstructed into computerized images. The concept includes proton spin tomographic techniques.Attention: Focusing on certain aspects of current experience to the exclusion of others. It is the act of heeding or taking notice or concentrating.Orientation: Awareness of oneself in relation to time, place and person.Visual Perception: The selecting and organizing of visual stimuli based on the individual's past experience.Sound Localization: Ability to determine the specific location of a sound source.Fixation, Ocular: The positioning and accommodation of eyes that allows the image to be brought into place on the FOVEA CENTRALIS of each eye.Reaction Time: The time from the onset of a stimulus until a response is observed.Binding Sites: The parts of a macromolecule that directly participate in its specific combination with another molecule.Saccades: An abrupt voluntary shift in ocular fixation from one point to another, as occurs in reading.Visual Fields: The total area or space visible in a person's peripheral vision with the eye looking straightforward.