Virus Information and Courses from MediaLab, Inc.

Molecular methodologies can be useful in the detection of a variety of diseases that are important public health issues such as:Chlamydia trachomatis (CT) Neisseria gonorrhoeae (GC)Human papillomavirus (HPV)Human Immunodeficiency Virus (HIV)Herpes Simplex Virus (HSV)Cytomegalovirus (CMV)In many clinical laboratories, traditional methods have been replaced by molecular methodologies because testing can occur for several pathogens in a single specimen. This is termed multiplex testing.

HIV consists of two basic components: a core of nucleic acid, called the genome, and a protein component that surrounds the genome, called a capsid. The genome carries the genetic information of the virus, while the capsid gives the virus its shape and protects the genome. The capsid is made up of subunits called capsomeres.

The Human Immunodeficiency Virus type-1 (HIV) belongs to the Family Retroviridae.In HIV, RNA is the template for the synthesis of DNA. This differs from most cellular biochemistry in which DNA is used as the template for the synthesis of RNA.The enzyme that transcribes the RNA for the synthesis of DNA is called reverse transcriptase.Because of the enzyme's activity, HIV is known as a retrovirus - retro implying reverse.

Genetic mutations in HIV are well known and are very likely, considering the presence of two RNA molecules per virus. Either or both RNA molecules can mutate. These mutations potentially lead to drug resistance or encourage the virus to evade the body's immune response. Mutations have created three major groups of HIV - M, N, and O. M is found in 99% of all the HIV cases in the world. N and O are primarily found in West African countries. N, though, infects only a very small number of individuals. The M group has subgroups lettered A to J. Subgroup B predominates in North America.

Like many other viruses, the HIV has a lipid membrane that covers the capsid. This envelope is acquired when the virus leaves a cell after replication. The HIV envelope has projections known as spikes, which contain specific chemical components that may assist the virus when it attaches to other cells.

As the envelope is being formed, the HIV leaves the cell. This stage is known as budding. The virus moves through the cell membrane, acquires an envelope, and exits into the extracellular environment. It is now ready to infect another cell.

Category C agents include: Nipah virus Hantaviruses Tick borne hemorrhagic fever viruses Tick borne encephalitis viruses Yellow fever Multi-drug resistant tuberculosis

As a healthcare worker, you come into contact with materials that may contain bloodborne pathogens. These are infectious organisms, usually viruses, which live in human blood and body fluids.The most important ones are: Hepatitis B Virus (HBV) Human Immunodeficiency Virus (HIV) Hepatitis C Virus (HCV)

Hepatitis B is caused by the Hepatitis B virus, or HBV.Following introduction of the virus into a susceptible person, it travels through the blood stream to the liver. Once in the liver the virus will multiply and cause hepatitis (inflammation of the liver).

HIV infection is caused by the human immunodeficiency virus.The infection occurs when HIV enters a person's bloodstream, where it attacks and kills the helper T-cells. Helper T-cells are part of a group of white blood cells, known as lymphocytes, which are essential to the body in fighting off infections.As the numbers of these cells decreases, so is the body's ability to fight infection.

A category A infectious substance is in a form that is capable of causing permanent disability or life-threatening or fatal disease in otherwise healthy humans or animals when exposure to it occurs. Exposure would occur if the substance were released from its protective packaging and a human or animal came into contact with it. Some examples of category A infectious substances include: Bacillus anthracis (cultures only) Brucella abortus (cultures only) Brucella melitensis (cultures only) Burkholderia mallei (cultures only) Clostridium botulinum (cultures only) Dengue virus (cultures only) Escherichia coli, verotoxigenic (cultures only) Ebola virus Francisella tularensis (cultures only) Hantaviruses causing hemorrhagic fever with renal syndrome Herpes B virus (cultures only) Human immunodeficiency virus (cultures only) Lassa virus Mycobacterium tuberculosis (cultures only) Poliovirus (cultures only) Rabies and other lyssaviruses (culture only) Shigella dysenteriae type I (cultures only) West Nile virus (cultures only) Yersinia pestis (cultures only)This is not an exhaustive list. Sometimes, deciding on the classification of an infectious substance requires professional judgement and involves knowing the medical history or symptoms of the source patient or animal and/or knowing the local epidemiological conditions at the time the patient specimen or culture was obtained. If there is doubt as to whether or not a substance meets the criteria of category A, it must be treated as a category A substance for shipping.

The most important bloodborne pathogens are: Hepatitis B and C & Human Immunodeficiency Virus (HIV). Hepatitis B is very infectious via the blood-borne route. 30% of needle-sticks from patients who are Hepatitis B will result in infection. Hepatitis C is much more common in the United States. HIV is rarely transmitted via needle-stick injury. Nevertheless, utmost care is needed, because of its very serious nature. HIV is not transmitted by casual contact.

To ensure the safety of those performing patient testing, controls do not contain HIV or the hepatitis B virus. Manufacturers place the same batch of control material into small vials. This allows only a small portion of the control to be handled while the remainder is stored until needed. Storage information for controls is printed on the label. These instructions should be followed carefully in order to prevent contamination or false results.

Many variations in morphology may be seen when examining Wright's stained peripheral blood smears. One method of classifying these variations in white cell morphology is based on the way the body responds to a stimulus, deficiency, or the presence of an inherited defect. This classification falls into three groups:Pathological: Cells may show abnormalities in appearance and/or function. The body is responding abnormally to a stimulus or inherited defect, resulting in physiological impairment in the patient. Nonpathological: Cells may show variation in morphology but their function is normal. Their presence does not cause physiological impairment. Reactive: Cells show variation in morphology but are functioning normally in response to a specific stimulus, such as a virus or bacteria. There is a disease process in progress to which the cells are responding. Although the morphology has varied from normal and their presence is significant, the body is responding normally to a stimulus.