Global Alert and Response (GAR)

Hepatitis B


albumin a water soluble protein. Serum albumin is found in blood plasma and is important for maintaining plasma volume and osmotic pressure of circulating blood. Albumin is synthesized in the liver. The inability to synthesize albumin is a predominant feature of chronic liver disease.

alkaline phosphatase any of a group of phosphatases showing activity at alkaline pH, which are normally measured collectively in blood serum. Serum levels are elevated in various conditions, among which hepatobiliary disorders.

alopecia loss of hair occurring at any site and from any cause.

ALT alanine aminotransferase an enzyme that interconverts L-alanine and D-alanine. It is a highly sensitive indicator of hepatocellular damage. When such damage occurs, ALT is released from the liver cells into the bloodstream, resulting in abnormally high serum levels. Normal ALT levels range from 10 to 32 U/l; in women, from 9 to 24 U/l. The normal range for infants is twice that of adults.

amino acids the basic units of proteins, each amino acid has a NH-C(R)-COOH structure, with a variable R group. There are altogether 20 types of naturally occurring amino acids.

antibody a protein molecule formed by the immune system which reacts specifically with the antigen that induced its synthesis. All antibodies are immune globulins.1

antigen any substance which can elicit in a vertebrate host the formation of specific antibodies or the generation of a specific population of lymphocytes reactive with the substance. Antigens may be protein or carbohydrate, lipid or nucleic acid, or contain elements of all or any of these as well as organic or inorganic chemical groups attached to protein or other macromolecule. Whether a material is an antigen in a particular host depends on whether the material is foreign to the host and also on the genetic makeup of the host, as well as on the dose and physical state of the antigen.1

arthralgia joint pain with objective findings of heat, redness, tenderness to touch, loss of motion, or swelling.   

AST aspartate aminotransferase the enzyme that catalyzes the reaction of aspartate with 2-oxoglutarate to give glutamate and oxaloacetate. Its concentration in blood may be raised in liver and heart diseases that are associated with damage to those tissues. Normal AST levels range from 8 to 20 U/l. AST levels fluctuate in response to the extent of cellular necrosis.1

B-cells also known as B lymphocytes. A class of white blood cells which carry out humoral immune response. They mature in the bone marrow.

bilirubin is the chief pigment of bile, formed mainly from the breakdown of haemoglobin. After formation it is transported in the plasma to the liver to be then excreted in the bile. Elevation of bile in the blood (>30 mg/l) causes jaundice.43

carcinoma a malignant epithelial tumour. This is the most frequent form of cancer. 

carrier is a person who has HBV (HCV, HDV) in his or her blood for longer than 6 months even if all symptoms have disappeared. Because the virus is present in the blood, it can be transmitted to others. The HBV carrier can be recognized by a specific blood test.

cirrhosis a chronic disease of the liver characterized by nodular regeneration of hepatocytes and diffuse fibrosis. It is caused by parenchymal necrosis followed by nodular proliferation of the surviving hepatocytes. The regenerating nodules and accompanying fibrosis interfere with blood flow through the liver and result in portal hypertension, hepatic insufficiency, jaundice and ascites.

codon the smallest unit of genetic material that can specify an amino acid residue in the synthesis of a polypeptide chain. The codon consists of three adjacent nucleotides. 

complete blood count chemical analysis of various substances in the blood performed with the aim of a) assessing the patient’s status by establishing normal levels for each individual patient, b) preventing disease by alerting to potentially dangerous levels of blood constituents that could lead to more serious conditions, c) establishing a diagnosis for already present pathologic conditions, and d) assessing a patient’s progress when a disturbance in blood chemistry already exists.

cytopathic that kills the cells.

cytoplasm the protoplasm of the cell which is outside of the nucleus. It consists of a continuous aqueous solution and the organelles and inclusions suspended in it. It is the site of most of the chemical activities of the cell.  

endemic prevalent continuously in some degree in a community or region.43

endoplasmic reticulum a network or system of folded membranes and interconnecting tubules distributed within the cytoplasm of eukaryotic cells. The membranes form enclosed or semienclosed spaces. The endoplasmic reticulum functions in storage and transport, and as a point of attachment of ribosomes during protein synthesis.  

enzyme any protein catalyst, i.e. substance which accelerates chemical reactions without itself being used up in the process. Many enzymes are specific to the substance on which they can act, called substrate. Enzymes  are present in all living matters and are involved in all the metabolic processes upon which life depends.

epidemic an outbreak of disease such that for a limited period a significantly greater number of persons in a community or region suffer from it than is normally the case. Thus an epidemic is a temporary increase in prevalence. Its extent and duration are determined by the interaction of such variables as the nature and infectivity of the casual agent, its mode of transmission and the degree of preexisting and newly acquired immunity.43

epitope also known as antigenic determinant. A localized region on the surface of an antigen which antibody molecules can identify and bind.

fulminant describes pathological conditions that develop suddenly and are of great severity.1

genome the total genetic information present in a cell. In diploid cells, the genetic information contained in one chromosome set.

Golgi apparatus a cytoplasmic organelle which is composed of flattened sacs resembling smooth endoplasmic reticulum. The sacs are often cup-shaped and located near the nucleus, the open side of the cup generally facing toward the cell surface. The function of the Golgi apparatus is to accept vesicles from the endoplasmic reticulum, to modify the contents, and to distribute the products to other parts of the cell or to the cellular environment.  

hepadnavirus family of single stranded DNA viruses of which hepatitis B virus (HBV) and woodchuck hepatitis virus (WHV) are members.     

hepatocytes are liver cells.1

humoral pertaining to the humors, or certain fluids, of the body.1

icterus see jaundice

IgG antibodies IgG is the most abundant of the circulating antibodies. It readily crosses the walls of blood vessels and enters tissue fluids. IgG also crosses the placenta and confers passive immunity from the mother to the fetus. IgG protects against bacteria, viruses, and toxins circulating in the blood and lymph.

IgM antibodies IgMs are the first circulating antibodies to appear in response to an antigen. However, their concentration in the blood declines rapidly. This is diagnostically useful, because the presence of IgM usually indicates a current infection by the pathogen causing its formation. IgM consists of five Y-shaped monomers arranged in a pentamer structure. The numerous antigen-binding sites make it very effective in agglutinating antigens. IgM is too large to cross the placenta and hence does not confer maternal immunity.

immune globulin (IG) is a sterile preparation of concentrated antibodies (immune globulins) recovered from pooled human plasma processed by cold ethanol fractionation. Only plasma that has tested negative for a) hepatitis B surface antigen (HBsAg), b) antibody to human immunodeficiency virus (HIV), and c) antibody to hepatitis C virus (HCV) is used to manufacture IG. IG is administered to protect against certain diseases through passive transfer of antibody. The IGs are broadly classified into five types on the basis of physical, antigenic and functional variations, labeled respectively IgM, IgG, IgA, IgE and IgD.    

immune system our body’s natural defence system, involving antibodies and a class of white blood cells called lymphocytes.

incidence the number of cases of a disease, abnormality, accident, etc., arising in a defined population during a stated period, expressed as a proportion, such as x cases per 1000 persons per year.1

interferon a protein produced in organisms infected by viruses, and effective at protecting those organisms from other virus infections. Interferons exert virus-nonspecific but host-specific antiviral activity by inducing the transcription of cellular genes coding for antiviral proteins that selectively inhibit the synthesis of viral DNA and proteins. Interferons also have immunoregulatory functions. Production of interferon can be stimulated by viral infection, especially by the presence of double stranded RNA, by intracellular parasites, by protozoa, and by bacteria and bacterial products. Interferons have been divided into three distinct types (α, β, and γ) associated with specific producer cells and functions, but all animal cells are capable of producing interferons, and certain producer cells (leukocytes and fibroblasts) produce more than one type (both α and β).

jaundice is a yellow discolouration of the skin and mucous membranes due to excess of bilirubin in the blood, also known as icterus.43

leukopenia an abnormal decrease in the number of leukocytes in the blood.

lumen the cavity or channel between a tube or tubular structure. 

lymphocyte a leukocyte of blood, bone marrow and lymphatic tissue. Lymphocytes play a major role in both cellular and humoral immunity, and thus several different functional and morphologic types must be recognized, i.e. the small, large, B-, and T-lymphocytes, with further morphologic distinction being made among the B-lymphocytes and functional distinction among T-lymphocytes.1

lymphoproliferative disease a neoplastic or systemic tumorlike proliferation of lymphocytes, as in lymphoid leukemia, malignant lymphomas, or in Waldenström’s macroglobulinemia.1

Major Histocompatibility Complex (MHC) originally defined as the genetic locus coding for those cell surface antigens presenting the major barrier to transplantation between individuals of the same species. Now known to be a cluster of genes on human chromosome 6 or mouse chromosome 17 that encodes the MHC molecules. These are the MHC class I molecules or proteins that present peptides generated in cytosol to CD8 T cells, and the MHC class II molecules or proteins that present peptides degraded in cellular vesicles to CD4 T cells. The MHC also encodes proteins involved in antigen processing and host defense. The MHC is the most polymorphic gene cluster in the human genome, having large numbers of alleles at several different loci. Because this polymorphism is usually detected using antibodies or specific T cells, the MHC proteins are often called major histocompatibility antigens.

myalgia pain in the muscles.

nucleotide a molecule formed from the combination of one nitrogenous base (purine or pyrimidine), a sugar (ribose or deoxyribose) and a phosphate group. It is a hydrolysis product of nucleic acid.1  

nucleus a membrane-bounded compartment in an eukaryotic cell which contains the genetic material and the nucleoli. The nucleus represents the control center of the cell. Nuclei divide by mitosis or meiosis.

plasma the liquid matrix in which the blood cells and blood proteins are suspended in. It contains an extensive variety of solutes dissolved in water. Water accounts for about 90% of blood plasma.

plasmid a small, circular DNA molecule, separate from the bacterial chromosome, capable of independent replication.

polymerase an enzyme which catalyzes the replication of DNA (DNA polymerase) or RNA (RNA polymerase).

prevalence is the number of instances of infections or of persons ill, or of any other event such as accidents, in a specified population, without any distinction between new and old cases.43

promoter a region of DNA usually occurring upstream from a gene coding region and acting as a controlling element in the expression of that gene. It serves as a recognition signal for an RNA polymerase and marks the site of initiation of transcription.

prophylaxis is the prevention of disease, or the preventive treatment of a recurrent disorder.43

protein large molecule made up of many amino acids chemically linked together by amide linkages. Biologically important as enzymes, structural protein and connective tissue.

prothrombin time a test used to measure the activity of clotting factors I, II, V, VII and X. Deficiency of any of these factors leads to a prolongation of the prothrombin time. The test is basic to any study of the coagulation process, and it helps in establishing and maintaining anticoagulant therapy.

reverse transcriptase an enzyme that catalyzes the formation of DNA using an RNA template, and is thus an RNA-dependent DNA polymerase. The name refers to the fact that the enzyme transcribes nucleic acids in the reverse order from the usual DNA-to-RNA transcription.

rigors stiffness.

RT-PCR reverse transcriptase - polymerase chain reaction. A technique commonly employed in molecular genetics through which it is possible to produce copies of DNA sequences rapidly.

seroconversion the production in a host of specific antibodies as a result of infection or immunization. The antibodies can be detected in the host’s blood serum following, but not preceding, infection or immunization.1  

serum is the clear, slightly yellow fluid which separates from blood when it clots. In composition it resembles blood plasma, but with fibrinogen removed. Sera containing antibodies and antitoxins against infections and toxins of various kinds (antisera) have been used extensively in prevention or treatment of various diseases.43

serum globulin all plasma proteins except albumin, which is not a globulin, and fibrinogen, which is not in the serum. The serum globulins are subdivided into α-, β-, and γ- globulins on the basis of their relative electrophoretic mobilities.

T-cells also known as T-lymphocytes. White blood cells which function in cell-mediated response. They originate from stem cells in the bone marrow but mature in the thymus.

thrombocytopenia a fewer than normal number of platelets per unit volume of blood, i.e. fewer than 130 x 109 platelets per liter.

titre a measure of the concentration or activity of an active substance.   

transcription the process by which a strand of RNA is synthesized with its sequence specified by a complementary strand of DNA, which acts as a template. The enzymes involved are called DNA-dependent RNA polymerases.

translation the process of forming a specific protein having its amino acid sequence determined by the codons of messenger RNA. Ribosomes and transfer RNA are necessary for translation.1

tumour a lump due to uncontrolled cell division, may be benign or malignant. Malignant tumours cause cancer. Tumours are able to spread to other parts of the body (metastasize) and begin secondary growths at these other sites.

vaccine an antigenic preparation used to produce active immunity to a disease to prevent or ameliorate the effects of infection with the natural or “wild” organism. Vaccines may be living, attenuated strains of viruses or bacteria which give rise to inapparent to trivial infections. Vaccines may also be killed or inactivated organisms or purified products derived from them. Formalin-inactivated toxins are used as vaccines against diphtheria and tetanus. Synthetically or genetically engineered antigens are currently being developed for use as vaccines. Some vaccines are effective by mouth, but most have to be given parenterally.1, 43

vaccinee person receiving a vaccine

virion a structurally complete virus, a viral particle.1

virus any of a number of small, obligatory intracellular parasites with a single type of nucleic acid, either DNA or RNA and no cell wall. The nucleic acid is enclosed in a structure called a capsid, which is composed of repeating protein subunits called capsomeres, with or without a lipid envelope. The complete infectious virus particle, called a virion, must rely on the metabolism of the cell it infects. Viruses are morphologically heterogeneous, occurring as spherical, filamentous, polyhedral, or pleomorphic particles. They are classified by the host infected, the type of nucleic acid, the symmetry of the capsid, and the presence or absence of an envelope.1