Pathology of viruses Infectious diseases lecture notes بروفسيورعلي التميمي

محاضرات Pathology of viruses Infectious diseases lecture notes البروفسیور د. علي التمیميالامراض للاقسام الطبیة لطلبة كلیة الرافدین الجامعة/Pathology of viruses Infectious diseases lecture notes

General

Introducing the viruses

– most frequent cause of human illness

– largest virus is the smallpox virus – .2-.3 microns; smallest is the polio virus (.028 microns)

– infectious agent in the virion; coat is the caspid, which surrounds the nucleic acid

– each virus must: 1) attach to the cell; 2) penetrate; 3) un-coat; 4) replicate

        – these stages are the virus cycle

– an eclipse phase almsot always occurrs between un-coating and replication; a virus integrated into the host genome, able to replicate with the dividing cell, is a provirus

– viremia means viruses in the bloodstream

– double-stranded DNA viruses

        – adenovirus, hepadnavirus family (hep B), herpes virus, papovirus family, poxvirus family (molluscum contagiosum, smallpox)

– RNA viruses

        – reovirus family, coronavirus family, orthomyxovirus family, picornavirus family, enterovirus subfamily, hepatitis A, rhinovirus family, paramyxovirus family, measels, mumps, parainfluenze, respiratory syncytial virus, retrovirus family, togavirus family, rubella, arboviruses

– DNA viruses replicate in the nucleus, and RNA viruses replicate in the cytoplasm

– viruses do harm by :

        1) destroying our cells as their progeny are released

        2) rendering infected cells non-functional

        3) exciting cell-mediated immunity, which destroys otherwise-healthy cells which happen to be infected by the virus

        4) causing cell overgrowth, which may be unsightly, a fertile ground of carcinogenesis, or full-blown malignancy

– neutralizing antibodies prevent or eliminate viral infection by binding to the viruses themselves

– cell-mediated immunity and interferon are also important

– viral inclusions are aggregates of virus proteins, visible by light microscopy

        -intranuclear

               – adenovirus

               – CMV

               – herpes simple I&II

               – herpes zoster

               – measles

        – intracytoplasmic

               – CMV

               – rabies

               – molluscum contagiosum

               – chlamydia

Virus respiratory disorders

– URI involve the nose, sinuses, throat, tonsils, and/or middle ear

– LRI involve the larynx, trachea, bronchi, alveoli, and/or pleura

– in a typical viral interstitial pneumonitis, inflammatory cells fill the alveolar spaces

– in fatal chest colds, there is more florid cell damage; death results when the airways are sufficiently damaged to allow fibrin to escape and block air flow and exchange

– rhinovirus – the common cold; URI directly, do not cause LRI

– coronaviruses – the second most common cause of the cold; do not cause LRI

– adenovirus – common colds, chest colds, red eyes, and/or GI upsets; necrosis is typical of the most severe adenovirus preumonitis, which can be fatal; pathologists notice enlarged, basophilic nuclei without any texture; these denote smudge cells

– influenza – primarily an infection of any and all parts of the respiratory tree