Prof. Dalia M. Mohsen Prof. In Microbiology

Viral the level of order and follows as thus, with the taxon suffixes classification starts at given in italics: Order Virales e.g. Herpesvirales Family Viridae e.g. Herpesviridae Genus Virus e.g. Herpes simplex virus Prof. Dalia M. Mohsen Prof. In Microbiology

Most clinically important viruses can be classified into groups according to their structural characters into: RNA Viruses A DNA Viruses B Prof. Dalia M. Mohsen Prof. In Microbiology

RNA Non-Enveloped virusesRNA Enveloped viruses Picorna viruses - Enteroviruses (Polio virus &Coxackievirus) - Hepato virus - Rhinoviruses Orthomyxoviruses (Influenza virus) ReovirusesParamyxoviruses (Measles, Mumps, Parainfluenza) CaicivirusesRhabdoviruses (Rabies virus) Astro virusesRetroviruses (HIV ) Togaviruses (Encephalitis viruses) Flaviviruses (Yellow fever,Dengue, HCV) Bunyaviruses Filoviruses Arenaviruses Corona viruses Delta virus Prof. Dalia M. Mohsen Prof. In Microbiology

DNA Non-Enveloped virusesDNA Enveloped viruses Herpes viruses - HSV 1&2 - Varicella - CMV Adenoviruses Hepadna virus (HBV)Papiloma virus Pox viruses (Smallpox, Cowpox)Parvoviruses Polyomaviruses Prof. Dalia M. Mohsen Prof. In Microbiology

Viruses cause disease after they: break through the natural protective barriers of the body. evade immune control. kill cells of an important tissue. Viral and host factors govern the severity of the disease they include: The strain of virus The inoculums size The general health of the infected person Prof. Dalia M. Mohsen Prof. In Microbiology

Entry into the body. Initiation of infection at a primary site. Activation of innate protections. An incubation period, when the virus is amplified and may spread to a secondary signs. Immune responses that limit and contribute to the disease. The symptoms of the disease are caused by tissue damage and systemic effects caused by the virus and the immune system. The body repairs the damage. Virus production in a tissue that release the virus to other people. Prof. Dalia M. Mohsen Prof. In Microbiology

Group Example (1)PicornavirusesPolioviruses (2)OrthomyxovirusesInfluenza viruses (3) Arthropod born virusesDengue Virus (4) Paramyxovirusesmeasles (5)RetroviridaeAIDS (6)Hepatitis virus(HAV, HBV, HCV) Prof. Dalia M. Mohsen Prof. In Microbiology

 Infection occurs by the ingestion of food or drink contaminated by stools of cases or carriers.  Incubation period is 7-14 days.  The organism multiplies in the oropharynx (tonsils) then patches in the intestine and excreted in stools.  Infection may stop at this stage i.e. in apparent infection.  Infection may continue and the virus passes to the deep cervical and deep mesenteric lymph nodes then it invades the blood stream. Viremia is associated with mild symptoms of fever, headache, nausea, and vomiting. The disease may be stopped at this stage i.e. abortive infection. Prof. Dalia M. Mohsen Prof. In Microbiology

1.Isolation of the virus from (stools, throat swab, blood, CS) in cell culture. Cytopathic effect appear in positive cases. 2.Detection of antibody by ELISA test. 3.Specific viral RNA can be identified by hybridization or PCR. Prof. Dalia M. Mohsen Prof. In Microbiology

 Three types of influenza virus are known; A, B and C.  Type A viruses infect humans and several types of animals, including birds, pigs, and horses.  Type B influenza is normally found only in humans.  Type C is mostly found in humans, but has also been found in pigs and dogs. Prof. Dalia M. Mohsen Prof. In Microbiology

 Influenza virus is a single stranded segmented RNA virus (gene segments).  The nucleocapside is helical and is surrounded by a lipoprotein envelope  The envelope is covered with two glycoprotein spikes, haemagglutinin(HA) and a neuraminidase(NA).  HA binds to the cell surface receptor (sialic acid) to initiate infection.  Changes in HA and NA determine the antigenicity of the virus and according to which influenza A virus includes 16 HA and 9 NA subtypes that are circulating in birds, human, swine and horses. Prof. Dalia M. Mohsen Prof. In Microbiology

Virus shift can take place when a person or animal is infected with two different subtypes of influenza.. Prof. Dalia M. Mohsen Prof. In Microbiology