Expiredvirology 4 you

in scientific fiction and reality  virus is a June premiere  virus was the most mysterious subject in medicine  bacterial filter discovery electron microscope we unveil this mystery

in this course we speak about history of discovery virus structure virus classifications  virus multiplication  virus pathogenesis zoonosis some important viruses hepatitis

Rabies is a vaccine preventable, zoonotic, viral disease. Once clinical symptoms appear, rabies is. Vaccinating dogs is the most

cost effective strategy for preventing rabies in people. post

exposure prophylaxis Post exposure prophylaxis(PEP) is the immediate treatment of a bite victim after rabies exposure.  This prevents virus entry into

the central nervous system, which results in imminent death. PEP consists of:•Extensive washing and local treatment of the bite wound or

scratch as soon as possible after a suspected exposure;•a course of potent and effective rabies vaccine and the administration of rabies immunoglobulin (RIG), if indicated

Laboratory diagnosis of viral infections  v1-Sampling

2-Virus isolation

3-Nucleic acid based methods

polymerase chain reaction

sequencingv4-Microscopy based methods immunofluorescence Electron microscopy 5-Host antibody detection 6-Hemagglutination assay

sampling temperatures (usually 4 °C) to preserve the virus and prevent bacterial or fungal growth. Sometimes multiple sites may also be sampled.

Types of samples include the following    A wide variety of samples can be used for virologic testing. The type of sample sent to the laboratory often depends on the type of viral infection being diagnosed and the test required  Proper sampling technique is essential to avoid potential pre-analytical errors .For example and stored at appropriate    stored at appropriate temperatures (usually 4 °C) to preserve the virus and prevent bacterial or fungal growth.  1.Nasopharyngeal swab

2.Blood  skin. Sputum, gargles and bronchial washings .Urine .Semen Faces  .Cerebrospinal fluid   .Tissues biopsies or post-mortem

Viruses are often isolated from the initial patient sample.   This allows the virus sample to be grown into larger quantities and allows a larger number of tests to be run on them. This is particularly important for samples that contain new or rare viruses for which diagnostic tests are not yet developed  Many viruses can be grown in cell culture in the lab.

To do this, the virus sample is mixed with cells, a process called adsorption, after which the cells become infected and produce more copies of the virus   Although different viruses often only grow in certain types of cells, there are cells that support the growth of a large variety of viruses and are a good starting point, for example, the African monkey kidney cell line (Vero cells), human lung fibroblasts (MRC-5), and human epidermoid carcinoma cells (HEp-2). One means of determining whether the cells are successfully  replicating the virus is to check for a change in cell morphology or for the presence of cell death using a microscope  Other viruses may require alternative methods for growth such as the inoculation of embryonated chicken eggs

(e.g. avian influenza viruses

[4]) or the intracranial inoculation of virus using newborn mice (e.g. lyssaviruses

[Nucleic acid based methods

Molecular techniques are the most specific and sensitive diagnostic tests

They are capable of detecting either the whole viral genome or parts of the viral genome.

In the past nucleic acid tests have mainly been used as a secondary test to confirm positive serological results However, as they become cheaper and more automated, they are increasingly becoming the primary tool for diagnostics  Polymerase chain reaction[

Detection of viral RNA and DNA genomes can be performed using polymerase chain reaction. This technique makes many copies of the virus genome using virus-specific probes. Variations of PCR such as nested reverse transcriptase PCR and real time PCR can also be used to determine viral loads in patient serum. This is often used to monitor treatment success in HIV cases. Sequencing[

Main article: Whole genome sequencing

Sequencing is the only diagnostic method that will provide the full sequence of a virus genome. Hence, it provides the most information about very small differences between two viruses that would look the same using other diagnostic tests

Viral replication is the formation of biological viruses during the infection process in the target host cells.  Viruses must first get into the cell before viral replication can occur.

Through the generation of abundant copies of its genome and packaging these copies, the virus continues infecting new hosts. Replication between viruses is greatly varied and depends on the type of genes involved in them Most DNA viruses assemble in the nucleus while most RNA viruses develop solely in cytoplasm. viruses multiply only in living cells. The host cell must provide the energy and synthetic machinery and the low- molecular-weight precursors for the synthesis of viral proteins and nucleic acids

virus  life cycle

1.Attachment

2.Entry,

3.Uncoating,

4.Transcription / mRNA production,

5.Synthesis of virus components,

6.Virion assembly and

Viral replication of a bacteriophage[3]

7- Release (Liberation Stage).