Viruses as Human Pathogen Pathogenesis and clinical picture

■ The parainfluenza viruses cause flulike infections, mainly in small children, which occasionally progress to bronchitis or even pneumonia. Occasionally, a dangerous croup syndrome develops. Bacterial superinfections are frequent, as are the usually harmless reinfections.

■ In mumps virus infections the virus first replicates in the respiratory tract, then causes a viremia, after which a parotitis is the main development as well as, fairly frequently, mumps meningitis. Complications include infection of various glandular organs. Orchitis can occur in postpuberty boys who contract mumps.

■ Measles. The pathogenesis of measles has not been fully explained. It is assumed that the virus, following primary replication in lymphoid tissues, is distributed hematogenously in two episodes. Thereafter the oral mucosa displays an enanthem and the tiny white "Koplik's spots." Then the fever once again rises and the typical measles exanthem manifests (Fig. 8.17). Possible complications include otitis in the form of a bacterial superinfection as well as pneumonia and encephalitis. A rare late sequel of measles (one case per million inhabitants) is subacute sclerosing panencephalitis (SSPE) in which nucleocapsids accummulate in brain cells, whereby few or no viral progeny are produced for lack of matrix protein. This disease occurs between the ages of one and 20, involves loss of memory and personality changes, and usually results in death within six to 12 months.

■ Nipah and Hendra virus infections are zoonoses endemic to Southeast Asia (Nipah) or Australia (Hendra). Both infections result in encephalitis

8 with relatively high lethality rates (up to 40%) and in some cases severe interstitial pneumonias.

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Essentials of Human Physiology

Essentials of Human Physiology

This ebook provides an introductory explanation of the workings of the human body, with an effort to draw connections between the body systems and explain their interdependencies. A framework for the book is homeostasis and how the body maintains balance within each system. This is intended as a first introduction to physiology for a college-level course.

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