Encephalitis Virus, St. Louis: A species of FLAVIVIRUS, one of the Japanese encephalitis virus group (ENCEPHALITIS VIRUSES, JAPANESE), which is the etiologic agent of ST. LOUIS ENCEPHALITIS in the United States, the Caribbean, and Central and South America.Encephalitis Virus, Japanese: A species of FLAVIVIRUS, one of the Japanese encephalitis virus group (ENCEPHALITIS VIRUSES, JAPANESE), which is the etiological agent of Japanese encephalitis found in Asia, southeast Asia, and the Indian subcontinent.Encephalitis, St. Louis: A viral encephalitis caused by the St. Louis encephalitis virus (ENCEPHALITIS VIRUS, ST. LOUIS), a FLAVIVIRUS. It is transmitted to humans and other vertebrates primarily by mosquitoes of the genus CULEX. The primary animal vectors are wild birds and the disorder is endemic to the midwestern and southeastern United States. Infections may be limited to an influenza-like illness or present as an ASEPTIC MENINGITIS or ENCEPHALITIS. Clinical manifestations of the encephalitic presentation may include SEIZURES, lethargy, MYOCLONUS, focal neurologic signs, COMA, and DEATH. (From Adams et al., Principles of Neurology, 6th ed, p750)MissouriEncephalitis, Japanese: A mosquito-borne encephalitis caused by the Japanese B encephalitis virus (ENCEPHALITIS VIRUS, JAPANESE) occurring throughout Eastern Asia and Australia. The majority of infections occur in children and are subclinical or have features limited to transient fever and gastrointestinal symptoms. Inflammation of the brain, spinal cord, and meninges may occur and lead to transient or permanent neurologic deficits (including a POLIOMYELITIS-like presentation); SEIZURES; COMA; and death. (From Adams et al., Principles of Neurology, 6th ed, p751; Lancet 1998 Apr 11;351(9109):1094-7)Encephalitis Virus, Venezuelan Equine: A species of ALPHAVIRUS that is the etiologic agent of encephalomyelitis in humans and equines. It is seen most commonly in parts of Central and South America.Flavivirus: A genus of FLAVIVIRIDAE containing several subgroups and many species. Most are arboviruses transmitted by mosquitoes or ticks. The type species is YELLOW FEVER VIRUS.Encephalitis Viruses, Tick-Borne: A subgroup of the genus FLAVIVIRUS that causes encephalitis and hemorrhagic fevers and is found in eastern and western Europe and the former Soviet Union. It is transmitted by TICKS and there is an associated milk-borne transmission from viremic cattle, goats, and sheep.Encephalitis Viruses: A collection of single-stranded RNA viruses scattered across the Bunyaviridae, Flaviviridae, and Togaviridae families whose common property is the ability to induce encephalitic conditions in infected hosts.Encephalitis: Inflammation of the BRAIN due to infection, autoimmune processes, toxins, and other conditions. Viral infections (see ENCEPHALITIS, VIRAL) are a relatively frequent cause of this condition.Encephalitis Virus, Eastern Equine: A species of ALPHAVIRUS causing encephalomyelitis in Equidae and humans. The virus ranges along the Atlantic seaboard of the United States and Canada and as far south as the Caribbean, Mexico, and parts of Central and South America. Infections in horses show a mortality of up to 90 percent and in humans as high as 80 percent in epidemics.Encephalitis Virus, Western Equine: A species of ALPHAVIRUS that is the etiologic agent of encephalomyelitis in humans and equines in the United States, southern Canada, and parts of South America.Encephalitis, Viral: Inflammation of brain parenchymal tissue as a result of viral infection. Encephalitis may occur as primary or secondary manifestation of TOGAVIRIDAE INFECTIONS; HERPESVIRIDAE INFECTIONS; ADENOVIRIDAE INFECTIONS; FLAVIVIRIDAE INFECTIONS; BUNYAVIRIDAE INFECTIONS; PICORNAVIRIDAE INFECTIONS; PARAMYXOVIRIDAE INFECTIONS; ORTHOMYXOVIRIDAE INFECTIONS; RETROVIRIDAE INFECTIONS; and ARENAVIRIDAE INFECTIONS.Encephalitis, Arbovirus: Infections of the brain caused by arthropod-borne viruses (i.e., arboviruses) primarily from the families TOGAVIRIDAE; FLAVIVIRIDAE; BUNYAVIRIDAE; REOVIRIDAE; and RHABDOVIRIDAE. Life cycles of these viruses are characterized by ZOONOSES, with birds and lower mammals serving as intermediate hosts. The virus is transmitted to humans by the bite of mosquitoes (CULICIDAE) or TICKS. Clinical manifestations include fever, headache, alterations of mentation, focal neurologic deficits, and COMA. (From Clin Microbiol Rev 1994 Jan;7(1):89-116; Walton, Brain's Diseases of the Nervous System, 10th ed, p321)Encephalomyelitis, Venezuelan Equine: A form of arboviral encephalitis endemic to Central America and the northern latitudes of South America. The causative organism (ENCEPHALITIS VIRUS, VENEZUELAN EQUINE) is transmitted to humans and horses via the bite of several mosquito species. Human viral infection may be asymptomatic or remain restricted to a mild influenza-like illness. Encephalitis, usually not severe, occurs in a small percentage of cases and may rarely feature SEIZURES and COMA. (From Joynt, Clinical Neurology, 1996, Ch26, pp9-10)Encephalitis Virus, Murray Valley: A species of FLAVIVIRUS, one of the Japanese encephalitis virus group (ENCEPHALITIS VIRUSES, JAPANESE), found in Australia and New Guinea. It causes a fulminating viremia resembling Japanese encephalitis (ENCEPHALITIS, JAPANESE).Encephalitis, Tick-Borne: Encephalitis caused by neurotropic viruses that are transmitted via the bite of TICKS. In Europe, the diseases are caused by ENCEPHALITIS VIRUSES, TICK-BORNE, which give rise to Russian spring-summer encephalitis, central European encephalitis, louping ill encephalitis, and related disorders. Powassan encephalitis occurs in North America and Russia and is caused by the Powassan virus. ASEPTIC MENINGITIS and rarely encephalitis may complicate COLORADO TICK FEVER which is endemic to mountainous regions of the western United States. (From Joynt, Clinical Neurology, 1996, Ch26, pp14-5)Encephalomyelitis, Equine: A group of ALPHAVIRUS INFECTIONS which affect horses and man, transmitted via the bites of mosquitoes. Disorders in this category are endemic to regions of South America and North America. In humans, clinical manifestations vary with the type of infection, and range from a mild influenza-like syndrome to a fulminant encephalitis. (From Joynt, Clinical Neurology, 1996, Ch26, pp8-10)Japanese Encephalitis Vaccines: Vaccines or candidate vaccines used to prevent infection with Japanese B encephalitis virus (ENCEPHALITIS VIRUS, JAPANESE).Encephalitis Viruses, Japanese: A subgroup of the genus FLAVIVIRUS which comprises a number of viral species that are the etiologic agents of human encephalitis in many different geographical regions. These include Japanese encephalitis virus (ENCEPHALITIS VIRUS, JAPANESE), St. Louis encephalitis virus (ENCEPHALITIS VIRUS, ST. LOUIS), Murray Valley encephalitis virus (ENCEPHALITIS VIRUS, MURRAY VALLEY), and WEST NILE VIRUS.West Nile virus: A species of FLAVIVIRUS, one of the Japanese encephalitis virus group (ENCEPHALITIS VIRUSES, JAPANESE). It can infect birds and mammals. In humans, it is seen most frequently in Africa, Asia, and Europe presenting as a silent infection or undifferentiated fever (WEST NILE FEVER). The virus appeared in North America for the first time in 1999. It is transmitted mainly by CULEX spp mosquitoes which feed primarily on birds, but it can also be carried by the Asian Tiger mosquito, AEDES albopictus, which feeds mainly on mammals.Culex: A genus of mosquitoes (CULICIDAE) commonly found in tropical regions. Species of this genus are vectors for ST. LOUIS ENCEPHALITIS as well as many other diseases of man and domestic and wild animals.Flavivirus Infections: Infections with viruses of the genus FLAVIVIRUS, family FLAVIVIRIDAE.Culicidae: A family of the order DIPTERA that comprises the mosquitoes. The larval stages are aquatic, and the adults can be recognized by the characteristic WINGS, ANIMAL venation, the scales along the wing veins, and the long proboscis. Many species are of particular medical importance.Limbic Encephalitis: A paraneoplastic syndrome marked by degeneration of neurons in the LIMBIC SYSTEM. Clinical features include HALLUCINATIONS, loss of EPISODIC MEMORY; ANOSMIA; AGEUSIA; TEMPORAL LOBE EPILEPSY; DEMENTIA; and affective disturbance (depression). Circulating anti-neuronal antibodies (e.g., anti-Hu; anti-Yo; anti-Ri; and anti-Ma2) and small cell lung carcinomas or testicular carcinoma are frequently associated with this syndrome.Encephalitis, Herpes Simplex: An acute (or rarely chronic) inflammatory process of the brain caused by SIMPLEXVIRUS infections which may be fatal. The majority of infections are caused by human herpesvirus 1 (HERPESVIRUS 1, HUMAN) and less often by human herpesvirus 2 (HERPESVIRUS 2, HUMAN). Clinical manifestations include FEVER; HEADACHE; SEIZURES; HALLUCINATIONS; behavioral alterations; APHASIA; hemiparesis; and COMA. Pathologically, the condition is marked by a hemorrhagic necrosis involving the medial and inferior TEMPORAL LOBE and orbital regions of the FRONTAL LOBE. (From Adams et al., Principles of Neurology, 6th ed, pp751-4)Antibodies, Viral: Immunoglobulins produced in response to VIRAL ANTIGENS.Encephalomyelitis, Eastern Equine: A form of arboviral encephalitis (primarily affecting equines) endemic to eastern regions of North America. The causative organism (ENCEPHALOMYELITIS VIRUS, EASTERN EQUINE) may be transmitted to humans via the bite of AEDES mosquitoes. Clinical manifestations include the acute onset of fever, HEADACHE, altered mentation, and SEIZURES followed by coma. The condition is fatal in up to 50% of cases. Recovery may be marked by residual neurologic deficits and EPILEPSY. (From Joynt, Clinical Neurology, 1996, Ch26, pp9-10)West Nile Fever: A mosquito-borne viral illness caused by the WEST NILE VIRUS, a FLAVIVIRUS and endemic to regions of Africa, Asia, and Europe. Common clinical features include HEADACHE; FEVER; maculopapular rash; gastrointestinal symptoms; and lymphadenopathy. MENINGITIS; ENCEPHALITIS; and MYELITIS may also occur. The disease may occasionally be fatal or leave survivors with residual neurologic deficits. (From Joynt, Clinical Neurology, 1996, Ch26, p13; Lancet 1998 Sep 5;352(9130):767-71)Arthritis-Encephalitis Virus, Caprine: A species of LENTIVIRUS, subgenus ovine-caprine lentiviruses (LENTIVIRUSES, OVINE-CAPRINE), closely related to VISNA-MAEDI VIRUS and causing acute encephalomyelitis; chronic arthritis; PNEUMONIA; MASTITIS; and GLOMERULONEPHRITIS in goats. It is transmitted mainly in the colostrum and milk.Horse Diseases: Diseases of domestic and wild horses of the species Equus caballus.Virus Cultivation: Process of growing viruses in live animals, plants, or cultured cells.Virus Replication: The process of intracellular viral multiplication, consisting of the synthesis of PROTEINS; NUCLEIC ACIDS; and sometimes LIPIDS, and their assembly into a new infectious particle.Vero Cells: A CELL LINE derived from the kidney of the African green (vervet) monkey, (CERCOPITHECUS AETHIOPS) used primarily in virus replication studies and plaque assays.RNA, Viral: Ribonucleic acid that makes up the genetic material of viruses.Arboviruses: Arthropod-borne viruses. A non-taxonomic designation for viruses that can replicate in both vertebrate hosts and arthropod vectors. Included are some members of the following families: ARENAVIRIDAE; BUNYAVIRIDAE; REOVIRIDAE; TOGAVIRIDAE; and FLAVIVIRIDAE. (From Dictionary of Microbiology and Molecular Biology, 2nd ed)Sindbis Virus: The type species of ALPHAVIRUS normally transmitted to birds by CULEX mosquitoes in Egypt, South Africa, India, Malaya, the Philippines, and Australia. It may be associated with fever in humans. Serotypes (differing by less than 17% in nucleotide sequence) include Babanki, Kyzylagach, and Ockelbo viruses.Neutralization Tests: The measurement of infection-blocking titer of ANTISERA by testing a series of dilutions for a given virus-antiserum interaction end-point, which is generally the dilution at which tissue cultures inoculated with the serum-virus mixtures demonstrate cytopathology (CPE) or the dilution at which 50% of test animals injected with serum-virus mixtures show infectivity (ID50) or die (LD50).Alphavirus: A genus of TOGAVIRIDAE, also known as Group A arboviruses, serologically related to each other but not to other Togaviridae. The viruses are transmitted by mosquitoes. The type species is the SINDBIS VIRUS.Viral Vaccines: Suspensions of attenuated or killed viruses administered for the prevention or treatment of infectious viral disease.RNA Viruses: Viruses whose genetic material is RNA.Horses: Large, hoofed mammals of the family EQUIDAE. Horses are active day and night with most of the day spent seeking and consuming food. Feeding peaks occur in the early morning and late afternoon, and there are several daily periods of rest.Arbovirus Infections: Infections caused by arthropod-borne viruses, general or unspecified.Cercopithecus aethiops: A species of CERCOPITHECUS containing three subspecies: C. tantalus, C. pygerythrus, and C. sabeus. They are found in the forests and savannah of Africa. The African green monkey (C. pygerythrus) is the natural host of SIMIAN IMMUNODEFICIENCY VIRUS and is used in AIDS research.Encephalomyelitis, Western Equine: A form of arboviral encephalitis (which primarily affects horses) endemic to western and central regions of NORTH AMERICA. The causative organism (ENCEPHALOMYELITIS VIRUS, WESTERN EQUINE) may be transferred to humans via the bite of mosquitoes (CULEX tarsalis and others). Clinical manifestations include headache and influenza-like symptoms followed by alterations in mentation, SEIZURES, and COMA. DEATH occurs in a minority of cases. Survivors may recover fully or be left with residual neurologic dysfunction, including PARKINSONISM, POSTENCEPHALITIC. (From Joynt, Clinical Neurology, 1996, Ch26, pp8-9)Antigens, Viral: Substances elaborated by viruses that have antigenic activity.Bird Diseases: Diseases of birds not considered poultry, therefore usually found in zoos, parks, and the wild. The concept is differentiated from POULTRY DISEASES which is for birds raised as a source of meat or eggs for human consumption, and usually found in barnyards, hatcheries, etc.Viral Plaque Assay: Method for measuring viral infectivity and multiplication in CULTURED CELLS. Clear lysed areas or plaques develop as the VIRAL PARTICLES are released from the infected cells during incubation. With some VIRUSES, the cells are killed by a cytopathic effect; with others, the infected cells are not killed but can be detected by their hemadsorptive ability. Sometimes the plaque cells contain VIRAL ANTIGENS which can be measured by IMMUNOFLUORESCENCE.Hemagglutination Inhibition Tests: Serologic tests in which a known quantity of antigen is added to the serum prior to the addition of a red cell suspension. Reaction result is expressed as the smallest amount of antigen which causes complete inhibition of hemagglutination.Vaccinia virus: The type species of ORTHOPOXVIRUS, related to COWPOX VIRUS, but whose true origin is unknown. It has been used as a live vaccine against SMALLPOX. It is also used as a vector for inserting foreign DNA into animals. Rabbitpox virus is a subspecies of VACCINIA VIRUS.Viral Envelope Proteins: Layers of protein which surround the capsid in animal viruses with tubular nucleocapsids. The envelope consists of an inner layer of lipids and virus specified proteins also called membrane or matrix proteins. The outer layer consists of one or more types of morphological subunits called peplomers which project from the viral envelope; this layer always consists of glycoproteins.Cricetinae: A subfamily in the family MURIDAE, comprising the hamsters. Four of the more common genera are Cricetus, CRICETULUS; MESOCRICETUS; and PHODOPUS.Hemoglobin M: A group of abnormal hemoglobins in which amino acid substitutions take place in either the alpha or beta chains but near the heme iron. This results in facilitated oxidation of the hemoglobin to yield excess methemoglobin which leads to cyanosis.Encephalitis Virus, California: A species in the ORTHOBUNYAVIRUS genus of the family BUNYAVIRIDAE. Serotypes are found in temperate and arctic regions and each is closely associated with a single species of vector mosquito. The vertebrate hosts are usually small mammals but several serotypes infect humans.Encephalitis, California: A viral infection of the brain caused by serotypes of California encephalitis virus (ENCEPHALITIS VIRUS, CALIFORNIA) transmitted to humans by the mosquito AEDES triseriatus. The majority of cases are caused by the LA CROSSE VIRUS. This condition is endemic to the midwestern United States and primarily affects children between 5-10 years of age. Clinical manifestations include FEVER; VOMITING; HEADACHE; and abdominal pain followed by SEIZURES, altered mentation, and focal neurologic deficits. (From Joynt, Clinical Neurology, 1996, Ch26, p13)Phylogeny: The relationships of groups of organisms as reflected by their genetic makeup.Cell Line: Established cell cultures that have the potential to propagate indefinitely.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.Receptors, Virus: Specific molecular components of the cell capable of recognizing and interacting with a virus, and which, after binding it, are capable of generating some signal that initiates the chain of events leading to the biological response.Insect Vectors: Insects that transmit infective organisms from one host to another or from an inanimate reservoir to an animate host.Virus Assembly: The assembly of VIRAL STRUCTURAL PROTEINS and nucleic acid (VIRAL DNA or VIRAL RNA) to form a VIRUS PARTICLE.Anti-N-Methyl-D-Aspartate Receptor Encephalitis: Disorder characterized by symptoms of CATATONIA; HYPOVENTILATION; DYSKINESIAS; ENCEPHALITIS; and SEIZURES followed by a reduced CONSCIOUSNESS. It is often followed by a viral-like prodrome. Many cases are self-limiting and respond well to IMMUNOMODULATORY THERAPIES against the NMDA RECEPTORS antibodies.Viral Nonstructural Proteins: Proteins encoded by a VIRAL GENOME that are produced in the organisms they infect, but not packaged into the VIRUS PARTICLES. Some of these proteins may play roles within the infected cell during VIRUS REPLICATION or act in regulation of virus replication or VIRUS ASSEMBLY.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.Virus Diseases: A general term for diseases produced by viruses.Defective Viruses: Viruses which lack a complete genome so that they cannot completely replicate or cannot form a protein coat. Some are host-dependent defectives, meaning they can replicate only in cell systems which provide the particular genetic function which they lack. Others, called SATELLITE VIRUSES, are able to replicate only when their genetic defect is complemented by a helper virus.Viral Proteins: Proteins found in any species of virus.Vaccines, Attenuated: Live vaccines prepared from microorganisms which have undergone physical adaptation (e.g., by radiation or temperature conditioning) or serial passage in laboratory animal hosts or infected tissue/cell cultures, in order to produce avirulent mutant strains capable of inducing protective immunity.Goats: Any of numerous agile, hollow-horned RUMINANTS of the genus Capra, in the family Bovidae, closely related to the SHEEP.Aedes: A genus of mosquitoes (CULICIDAE) frequently found in tropical and subtropical regions. YELLOW FEVER and DENGUE are two of the diseases that can be transmitted by species of this genus.Virus Shedding: The expelling of virus particles from the body. Important routes include the respiratory tract, genital tract, and intestinal tract. Virus shedding is an important means of vertical transmission (INFECTIOUS DISEASE TRANSMISSION, VERTICAL).Birds: Warm-blooded VERTEBRATES possessing FEATHERS and belonging to the class Aves.Lentivirus Infections: Virus diseases caused by the Lentivirus genus. They are multi-organ diseases characterized by long incubation periods and persistent infection.Brain: The part of CENTRAL NERVOUS SYSTEM that is contained within the skull (CRANIUM). Arising from the NEURAL TUBE, the embryonic brain is comprised of three major parts including PROSENCEPHALON (the forebrain); MESENCEPHALON (the midbrain); and RHOMBENCEPHALON (the hindbrain). The developed brain consists of CEREBRUM; CEREBELLUM; and other structures in the BRAIN STEM.Dengue Virus: A species of the genus FLAVIVIRUS which causes an acute febrile and sometimes hemorrhagic disease in man. Dengue is mosquito-borne and four serotypes are known.Czechoslovakia: Created as a republic in 1918 by Czechs and Slovaks from territories formerly part of the Austro-Hungarian Empire. The country split into the Czech Republic and Slovakia 1 January 1993.Viremia: The presence of viruses in the blood.Sequence Analysis, DNA: A multistage process that includes cloning, physical mapping, subcloning, determination of the DNA SEQUENCE, and information analysis.Measles virus: The type species of MORBILLIVIRUS and the cause of the highly infectious human disease MEASLES, which affects mostly children.Simian virus 40: A species of POLYOMAVIRUS originally isolated from Rhesus monkey kidney tissue. It produces malignancy in human and newborn hamster kidney cell cultures.Enzyme-Linked Immunosorbent Assay: An immunoassay utilizing an antibody labeled with an enzyme marker such as horseradish peroxidase. While either the enzyme or the antibody is bound to an immunosorbent substrate, they both retain their biologic activity; the change in enzyme activity as a result of the enzyme-antibody-antigen reaction is proportional to the concentration of the antigen and can be measured spectrophotometrically or with the naked eye. Many variations of the method have been developed.Cytopathogenic Effect, Viral: Visible morphologic changes in cells infected with viruses. It includes shutdown of cellular RNA and protein synthesis, cell fusion, release of lysosomal enzymes, changes in cell membrane permeability, diffuse changes in intracellular structures, presence of viral inclusion bodies, and chromosomal aberrations. It excludes malignant transformation, which is CELL TRANSFORMATION, VIRAL. Viral cytopathogenic effects provide a valuable method for identifying and classifying the infecting viruses.Plant Viruses: Viruses parasitic on plants higher than bacteria.Goat Diseases: Diseases of the domestic or wild goat of the genus Capra.Virion: The infective system of a virus, composed of the viral genome, a protein core, and a protein coat called a capsid, which may be naked or enclosed in a lipoprotein envelope called the peplos.Rabies virus: The type species of LYSSAVIRUS causing rabies in humans and other animals. Transmission is mostly by animal bites through saliva. The virus is neurotropic multiplying in neurons and myotubes of vertebrates.Yellow fever virus: The type species of the FLAVIVIRUS genus. Principal vector transmission to humans is by AEDES spp. mosquitoes.DNA Viruses: Viruses whose nucleic acid is DNA.Replicon: Any DNA sequence capable of independent replication or a molecule that possesses a REPLICATION ORIGIN and which is therefore potentially capable of being replicated in a suitable cell. (Singleton & Sainsbury, Dictionary of Microbiology and Molecular Biology, 2d ed)Disease Outbreaks: Sudden increase in the incidence of a disease. The concept includes EPIDEMICS and PANDEMICS.Genes, Viral: The functional hereditary units of VIRUSES.Antiviral Agents: Agents used in the prophylaxis or therapy of VIRUS DISEASES. Some of the ways they may act include preventing viral replication by inhibiting viral DNA polymerase; binding to specific cell-surface receptors and inhibiting viral penetration or uncoating; inhibiting viral protein synthesis; or blocking late stages of virus assembly.Influenza A Virus, H1N1 Subtype: A subtype of INFLUENZA A VIRUS with the surface proteins hemagglutinin 1 and neuraminidase 1. The H1N1 subtype was responsible for the Spanish flu pandemic of 1918.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.Dengue: An acute febrile disease transmitted by the bite of AEDES mosquitoes infected with DENGUE VIRUS. It is self-limiting and characterized by fever, myalgia, headache, and rash. SEVERE DENGUE is a more virulent form of dengue.Cross Reactions: Serological reactions in which an antiserum against one antigen reacts with a non-identical but closely related antigen.Influenza A Virus, H5N1 Subtype: A subtype of INFLUENZA A VIRUS comprised of the surface proteins hemagglutinin 5 and neuraminidase 1. The H5N1 subtype, frequently referred to as the bird flu virus, is endemic in wild birds and very contagious among both domestic (POULTRY) and wild birds. It does not usually infect humans, but some cases have been reported.Reverse Transcriptase Polymerase Chain Reaction: A variation of the PCR technique in which cDNA is made from RNA via reverse transcription. The resultant cDNA is then amplified using standard PCR protocols.RNA Helicases: A family of proteins that promote unwinding of RNA during splicing and translation.Viral Structural Proteins: Viral proteins that are components of the mature assembled VIRUS PARTICLES. They may include nucleocapsid core proteins (gag proteins), enzymes packaged within the virus particle (pol proteins), and membrane components (env proteins). These do not include the proteins encoded in the VIRAL GENOME that are produced in infected cells but which are not packaged in the mature virus particle,i.e. the so called non-structural proteins (VIRAL NONSTRUCTURAL PROTEINS).DNA, Viral: Deoxyribonucleic acid that makes up the genetic material of viruses.Ochlerotatus: A genus of mosquitoes in the family CULICIDAE. A large number of the species are found in the neotropical part of the Americas.Hemagglutination, Viral: Agglutination of ERYTHROCYTES by a virus.Famous PersonsVirus Inactivation: Inactivation of viruses by non-immune related techniques. They include extremes of pH, HEAT treatment, ultraviolet radiation, IONIZING RADIATION; DESICCATION; ANTISEPTICS; DISINFECTANTS; organic solvents, and DETERGENTS.Virus Attachment: The binding of virus particles to receptors on the host cell surface. For enveloped viruses, the virion ligand is usually a surface glycoprotein as is the cellular receptor. For non-enveloped viruses, the virus CAPSID serves as the ligand.Toxoplasmosis, Cerebral: Infections of the BRAIN caused by the protozoan TOXOPLASMA gondii that primarily arise in individuals with IMMUNOLOGIC DEFICIENCY SYNDROMES (see also AIDS-RELATED OPPORTUNISTIC INFECTIONS). The infection may involve the brain diffusely or form discrete abscesses. Clinical manifestations include SEIZURES, altered mentation, headache, focal neurologic deficits, and INTRACRANIAL HYPERTENSION. (From Joynt, Clinical Neurology, 1998, Ch27, pp41-3)ArgentinaVirus Activation: The mechanism by which latent viruses, such as genetically transmitted tumor viruses (PROVIRUSES) or PROPHAGES of lysogenic bacteria, are induced to replicate and then released as infectious viruses. It may be effected by various endogenous and exogenous stimuli, including B-cell LIPOPOLYSACCHARIDES, glucocorticoid hormones, halogenated pyrimidines, IONIZING RADIATION, ultraviolet light, and superinfecting viruses.Influenza A Virus, H3N2 Subtype: A subtype of INFLUENZA A VIRUS comprised of the surface proteins hemagglutinin 3 and neuraminidase 2. The H3N2 subtype was responsible for the Hong Kong flu pandemic of 1968.Hepatitis B virus: The type species of the genus ORTHOHEPADNAVIRUS which causes human HEPATITIS B and is also apparently a causal agent in human HEPATOCELLULAR CARCINOMA. The Dane particle is an intact hepatitis virion, named after its discoverer. Non-infectious spherical and tubular particles are also seen in the serum.Genetic Vectors: DNA molecules capable of autonomous replication within a host cell and into which other DNA sequences can be inserted and thus amplified. Many are derived from PLASMIDS; BACTERIOPHAGES; or VIRUSES. They are used for transporting foreign genes into recipient cells. Genetic vectors possess a functional replicator site and contain GENETIC MARKERS to facilitate their selective recognition.Virology: The study of the structure, growth, function, genetics, and reproduction of viruses, and VIRUS DISEASES.Insectivora: An order of insect eating MAMMALS including MOLES; SHREWS; HEDGEHOGS and tenrecs.Ixodes: The largest genus of TICKS in the family IXODIDAE, containing over 200 species. Many infest humans and other mammals and several are vectors of diseases such as LYME DISEASE, tick-borne encephalitis (ENCEPHALITIS, TICK-BORNE), and KYASANUR FOREST DISEASE.Antibodies, Neutralizing: Antibodies that reduce or abolish some biological activity of a soluble antigen or infectious agent, usually a virus.Communicable Diseases, Emerging: Infectious diseases that are novel in their outbreak ranges (geographic and host) or transmission mode.Vaccines, Synthetic: Small synthetic peptides that mimic surface antigens of pathogens and are immunogenic, or vaccines manufactured with the aid of recombinant DNA techniques. The latter vaccines may also be whole viruses whose nucleic acids have been modified.Immunoglobulin M: A class of immunoglobulin bearing mu chains (IMMUNOGLOBULIN MU-CHAINS). IgM can fix COMPLEMENT. The name comes from its high molecular weight and originally being called a macroglobulin.Respiratory Syncytial Viruses: A group of viruses in the PNEUMOVIRUS genus causing respiratory infections in various mammals. Humans and cattle are most affected but infections in goats and sheep have also been reported.Ticks: Blood-sucking acarid parasites of the order Ixodida comprising two families: the softbacked ticks (ARGASIDAE) and hardbacked ticks (IXODIDAE). Ticks are larger than their relatives, the MITES. They penetrate the skin of their host by means of highly specialized, hooked mouth parts and feed on its blood. Ticks attack all groups of terrestrial vertebrates. In humans they are responsible for many TICK-BORNE DISEASES, including the transmission of ROCKY MOUNTAIN SPOTTED FEVER; TULAREMIA; BABESIOSIS; AFRICAN SWINE FEVER; and RELAPSING FEVER. (From Barnes, Invertebrate Zoology, 5th ed, pp543-44)Vaccination: Administration of vaccines to stimulate the host's immune response. This includes any preparation intended for active immunological prophylaxis.FloridaSimian immunodeficiency virus: Species of the genus LENTIVIRUS, subgenus primate immunodeficiency viruses (IMMUNODEFICIENCY VIRUSES, PRIMATE), that induces acquired immunodeficiency syndrome in monkeys and apes (SAIDS). The genetic organization of SIV is virtually identical to HIV.La Crosse virus: A serotype of the species California encephalitis virus (ENCEPHALITIS VIRUS, CALIFORNIA), in the genus ORTHOBUNYAVIRUS, causing human MENINGOENCEPHALITIS. This is the agent most responsible for California encephalitis (ENCEPHALITIS, CALIFORNIA), the most prevalent mosquito-borne disease recognized in the United States.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.Epitopes: Sites on an antigen that interact with specific antibodies.Time Factors: Elements of limited time intervals, contributing to particular results or situations.Capsid Proteins: Proteins that form the CAPSID of VIRUSES.Capsid: The outer protein protective shell of a virus, which protects the viral nucleic acid.Vesicular stomatitis Indiana virus: The type species of VESICULOVIRUS causing a disease symptomatically similar to FOOT-AND-MOUTH DISEASE in cattle, horses, and pigs. It may be transmitted to other species including humans, where it causes influenza-like symptoms.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).Genome, Viral: The complete genetic complement contained in a DNA or RNA molecule in a virus.Virus Latency: The ability of a pathogenic virus to lie dormant within a cell (latent infection). In eukaryotes, subsequent activation and viral replication is thought to be caused by extracellular stimulation of cellular transcription factors. Latency in bacteriophage is maintained by the expression of virally encoded repressors.Complement Fixation Tests: Serologic tests based on inactivation of complement by the antigen-antibody complex (stage 1). Binding of free complement can be visualized by addition of a second antigen-antibody system such as red cells and appropriate red cell antibody (hemolysin) requiring complement for its completion (stage 2). Failure of the red cells to lyse indicates that a specific antigen-antibody reaction has taken place in stage 1. If red cells lyse, free complement is present indicating no antigen-antibody reaction occurred in stage 1.Rodent Diseases: Diseases of rodents of the order RODENTIA. This term includes diseases of Sciuridae (squirrels), Geomyidae (gophers), Heteromyidae (pouched mice), Castoridae (beavers), Cricetidae (rats and mice), Muridae (Old World rats and mice), Erethizontidae (porcupines), and Caviidae (guinea pigs).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.Siberia: A region, north-central Asia, largely in Russia. It extends from the Ural Mountains to the Pacific Ocean and from the Arctic Ocean to central Kazakhstan and the borders of China and Mongolia.Disease Models, Animal: Naturally occurring or experimentally induced animal diseases with pathological processes sufficiently similar to those of human diseases. They are used as study models for human diseases.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.Swine Diseases: Diseases of domestic swine and of the wild boar of the genus Sus.Mice, Inbred BALB CCerebrospinal Fluid: A watery fluid that is continuously produced in the CHOROID PLEXUS and circulates around the surface of the BRAIN; SPINAL CORD; and in the CEREBRAL VENTRICLES.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.Chickens: Common name for the species Gallus gallus, the domestic fowl, in the family Phasianidae, order GALLIFORMES. It is descended from the red jungle fowl of SOUTHEAST ASIA.Alphavirus Infections: Virus diseases caused by members of the ALPHAVIRUS genus of the family TOGAVIRIDAE.Recombination, Genetic: Production of new arrangements of DNA by various mechanisms such as assortment and segregation, CROSSING OVER; GENE CONVERSION; GENETIC TRANSFORMATION; GENETIC CONJUGATION; GENETIC TRANSDUCTION; or mixed infection of viruses.Host-Pathogen Interactions: The interactions between a host and a pathogen, usually resulting in disease.Antibodies, Monoclonal: Antibodies produced by a single clone of cells.Rodentia: A mammalian order which consists of 29 families and many genera.Hemagglutinin Glycoproteins, Influenza Virus: Membrane glycoproteins from influenza viruses which are involved in hemagglutination, virus attachment, and envelope fusion. Fourteen distinct subtypes of HA glycoproteins and nine of NA glycoproteins have been identified from INFLUENZA A VIRUS; no subtypes have been identified for Influenza B or Influenza C viruses.Cells, Cultured: Cells propagated in vitro in special media conducive to their growth. Cultured cells are used to study developmental, morphologic, metabolic, physiologic, and genetic processes, among others.South AmericaMumps virus: The type species of RUBULAVIRUS that causes an acute infectious disease in humans, affecting mainly children. Transmission occurs by droplet infection.VenezuelaGene Expression Regulation, Viral: Any of the processes by which cytoplasmic factors influence the differential control of gene action in viruses.Sigmodontinae: A subfamily of the family MURIDAE comprised of 69 genera. New World mice and rats are included in this subfamily.Semliki forest virus: A species of ALPHAVIRUS isolated in central, eastern, and southern Africa.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.Disease Vectors: Invertebrates or non-human vertebrates which transmit infective organisms from one host to another.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)Serologic Tests: Diagnostic procedures involving immunoglobulin reactions.Amebiasis: Infection with any of various amebae. It is an asymptomatic carrier state in most individuals, but diseases ranging from chronic, mild diarrhea to fulminant dysentery may occur.Animals, Wild: Animals considered to be wild or feral or not adapted for domestic use. It does not include wild animals in zoos for which ANIMALS, ZOO is available.Culture Techniques: Methods of maintaining or growing biological materials in controlled laboratory conditions. These include the cultures of CELLS; TISSUES; organs; or embryo in vitro. Both animal and plant tissues may be cultured by a variety of methods. Cultures may derive from normal or abnormal tissues, and consist of a single cell type or mixed cell types.Serial Passage: Inoculation of a series of animals or in vitro tissue with an infectious bacterium or virus, as in VIRULENCE studies and the development of vaccines.Oncogenic Viruses: Viruses that produce tumors.Hemagglutinins, Viral: Specific hemagglutinin subtypes encoded by VIRUSES.Chick Embryo: The developmental entity of a fertilized chicken egg (ZYGOTE). The developmental process begins about 24 h before the egg is laid at the BLASTODISC, a small whitish spot on the surface of the EGG YOLK. After 21 days of incubation, the embryo is fully developed before hatching.Mice, Inbred ICRSimplexvirus: A genus of the family HERPESVIRIDAE, subfamily ALPHAHERPESVIRINAE, consisting of herpes simplex-like viruses. The type species is HERPESVIRUS 1, HUMAN.Immunization: Deliberate stimulation of the host's immune response. ACTIVE IMMUNIZATION involves administration of ANTIGENS or IMMUNOLOGIC ADJUVANTS. PASSIVE IMMUNIZATION involves administration of IMMUNE SERA or LYMPHOCYTES or their extracts (e.g., transfer factor, immune RNA) or transplantation of immunocompetent cell producing tissue (thymus or bone marrow).Encephalitis, Varicella Zoster: Inflammation of brain tissue caused by infection with the varicella-zoster virus (HERPESVIRUS 3, HUMAN). This condition is associated with immunocompromised states, including the ACQUIRED IMMUNODEFICIENCY SYNDROME. Pathologically, the virus tends to induce a vasculopathy and infect oligodendrocytes and ependymal cells, leading to CEREBRAL INFARCTION, multifocal regions of demyelination, and periventricular necrosis. Manifestations of varicella encephalitis usually occur 5-7 days after onset of HERPES ZOSTER and include HEADACHE; VOMITING; lethargy; focal neurologic deficits; FEVER; and COMA. (From Joynt, Clinical Neurology, 1996, Ch 26, pp29-32; Hum Pathol 1996 Sep;27(9):927-38)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.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)Genetic Variation: Genotypic differences observed among individuals in a population.Parainfluenza Virus 1, Human: A species of RESPIROVIRUS also called hemadsorption virus 2 (HA2), which causes laryngotracheitis in humans, especially children.Base Sequence: The sequence of PURINES and PYRIMIDINES in nucleic acids and polynucleotides. It is also called nucleotide sequence.Mosaic Viruses: Viruses which produce a mottled appearance of the leaves of plants.Herpesvirus 1, Human: The type species of SIMPLEXVIRUS causing most forms of non-genital herpes simplex in humans. Primary infection occurs mainly in infants and young children and then the virus becomes latent in the dorsal root ganglion. It then is periodically reactivated throughout life causing mostly benign conditions.Immunoglobulin G: The major immunoglobulin isotype class in normal human serum. There are several isotype subclasses of IgG, for example, IgG1, IgG2A, and IgG2B.Visna-maedi virus: A species of LENTIVIRUS, subgenus ovine-caprine lentiviruses (LENTIVIRUSES, OVINE-CAPRINE), that can cause chronic pneumonia (maedi), mastitis, arthritis, and encephalomyelitis (visna) in sheep. Maedi is a progressive pneumonia of sheep which is similar to but not the same as jaagsiekte (PULMONARY ADENOMATOSIS, OVINE). Visna is a demyelinating leukoencephalomyelitis of sheep which is similar to but not the same as SCRAPIE.Genotype: The genetic constitution of the individual, comprising the ALLELES present at each GENETIC LOCUS.Hemagglutination Tests: Sensitive tests to measure certain antigens, antibodies, or viruses, using their ability to agglutinate certain erythrocytes. (From Stedman, 26th ed)Central Nervous System Infections: Pathogenic infections of the brain, spinal cord, and meninges. DNA VIRUS INFECTIONS; RNA VIRUS INFECTIONS; BACTERIAL INFECTIONS; MYCOPLASMA INFECTIONS; SPIROCHAETALES INFECTIONS; fungal infections; PROTOZOAN INFECTIONS; HELMINTHIASIS; and PRION DISEASES may involve the central nervous system as a primary or secondary process.Hepatitis A virus: A species in the genus HEPATOVIRUS containing one serotype and two strains: HUMAN HEPATITIS A VIRUS and Simian hepatitis A virus causing hepatitis in humans (HEPATITIS A) and primates, respectively.