Rna Viruses

Fig. 2-1 Shapes and sizes of viruses of families that include human pathogens. The virions are drawn to scale, but artistic license has been used in representing then structure In some, the cross-sectional structure of capsid and envelope is shown, with a representation of the genome, with the very small virions, only size and symmetry are depicted Genus. Erylhroi'irus (human parvovirus B19) Genus Deprmlmnrns (adeno-associated viruses) Parvoviruses (parvus, small) are about 20 nm in diameter,...

Clinical Features of Hepatitis B

Most HBV infections are subclinical, particularly during childhood, but about one-third of adult infections are icteric. The course of acute viral hepatitis is conventionally divided into three phases (1) preicteric, (2) icteric, and (3) convalescent. Following a long incubation period of 6-26 weeks in the case of hepatitis B, the preicteric (prodromal) phase commences with malaise, lethargy, anorexia, and commonly nausea, vomiting, and pain in the right upper abdominal quandrant. A minority of...

Herpesviridae

Properties of Herpesviridae 318 All herpesviruses have the capacity to persist in their hosts indefinitely in the form of an episome in the nucleus of the cells that harbor them. Virtually every vertebrate species that has been carefully searched is found to support at least one host-specific herpesvirus which has evolved with that host species for millennia. Sometimes, as in humans, host-specific herpesviruses of different subfamilies occupy distinct ecologic niches, noncompetitively, in...

Viral Diseases of the

Conjunctivitis Adenoviruses 3, 4, 7, others Corneal ulceration Ophthalmic zoster Pandemics radiculomyelitis Sandfly fever Dengue Measles Rubella Keratoconjunctivitis Adenoviruses 8, 37, others Keratoconjunctivitis Adenoviruses 8, 37, others ertteroviral infections, and it is an important component of the dengue-like syndromes caused by many arboviruses, such as phlebotomus (sandfly) fever. Infections with adenoviruses, notably types 3, 4, and 7 in children, present as a bilateral follicular...

Poxviridae

Child Moiiuscum Contagiosum Diseases

Human Infections with Orthopoxviruses 353 Human Infections with Parapoxviruses 356 The family Poxviridae is divided into two subfamilies, Clmrdopoxviriniie poxviruses of vertebrates and Eiitoniopoxvirinae poxviruses of insects only the former are of importance in medicine. The subfamily Chordopoxvirinae contains eight genera, distinguished on the basis of genetic, antigenic, and morphologic differences. Several poxviruses causes diseases in humans smallpox now extinct , vaccinia including a...

Viral Pancreatitis and Diabetes

Several viruses occasionally infect the pancreas in humans. Mumps, for example, can be complicated by severe pancreatitis, and coxsackie B viruses or various other enteroviruses have been incriminated also. Of greater research interest is the question of whether viruses may trigger juvenile diabetes mellitus of the insulin-dependent type IDDM . Children born with the congenital rubella syndrome quite often develop IDDM before the age of 20. Mumps infections often affect the p cells of the...

Parainfluenza Viruses

Parainfluenza viruses are common human respiratory pathogens, in the main they produce relatively harmless upper respiratory tract infections URTI , but they are also the commonest cause of a more serious condition in young children known as croup and occasionally cause pneumonia. Human parainfluenza virus types 1 and 3 belong to the genus Paramyxovirus, whereas types 2, 4a, and 4b are now classified with mumps virus in the genus Rubulavirus. Primary infection, typically in a young child,...

Other Enteroviruses

Most enteroviruses are presumed to enter the body via ingestion and to grow well in both the throat and the intestinal tract, but they are shed in the feces for much longer than in respiratory secretions. Dissemination via the bloodstream is doubtless the route of spread to the wide range of target organs susceptible to attack. Little is known of the factors that determine the tropism of different enteroviruses, for example, the predilection of coxsackie B viruses for muscle or of enterovirus...

Genetic Changes in Influenza A Virus

Human influenza virus was first isolated in 1933 Since that time human influenza viruses have been recovered from all parts of the world, and their antigenic properties have been studied in considerable detail, thus providing an opportunity for observing continuing evolutionary changes. Influenza A virus occurs in humans, swine, horses, birds, and aquatic mammals. Subtypes are classified according to the two envelope antigens, the hemagglutinin HA, or H and neuraminidase NA, or N All of the...

Viral Damage to Tissues and Organs

Diarrhea Rotavirus

The mechanisms by which viruses damage cells were discussed at the cellular and subcellular levels in Chapter 5. Here we apply these concepts at the level of tissues and organs. The severity of disease In humans is not necessarily correlated with the degree of cytopathology produced by the virus in vitro. Many viruses that are cytocidal in cultured cells generally do not produce clinical disease for example, enteroviruses, which cause severe cytopathic effects CPE in cultured human cells,...

Papillomaviruses

Host species-specific papillomaviruses have been found in many animals and birds. Most cause benign papillomas in the skin or mucous membranes. There are numerous human papillomaviruses HPV , most displaying a predilection for a particular site in the body. Some have oncogenic potential. Fig. 18-1 Pajtovaviridac A flapilbmamrtii, B Pnltfiminvirus C Polt ontavmis, empty virions Bar, 100 nm. Courtesy Dr t A FolfeH Fig. 18-1 Pajtovaviridac A flapilbmamrtii, B Pnltfiminvirus C Polt ontavmis, empty...

Mechanisms of Survival of Viruses in Nature

Perpetuation of a virus in nature depends on the maintenance of serial infections, that is, a chain of transmission the occurrence of disease is neither required nor necessarily advantageous. Indeed, although clinical cases may be somewhat more productive sources of infectious virus than inapparent infections, the latter are generally more numerous and do not restrict the movement of infectious individuals, and thus provide a major mechanism of viral dissemination. As our knowledge of the...

Viral Skin Rashes

Types Viral Rashes

Many viruses involve the skin in one way or another Table 36-4 Some, such as papillomaviruses, poxviruses, and recurrent herpes simplex, produce relatively localized crops of lesions and few if any systemic symptoms. Others, such as those causing the childhood exanthemata, produce a generalized rash as part of a wider clinical syndrome that follows a systemic infection. These rashes vary greatly in their anatomic distribution and in the morphology of the individual lesions. They are classified...

Transcription

Dsdna Papovavirus

Having outlined the several contrasting strategies of expression of the viral genome, we are now in a position to describe in more detail the processes of transcription, translation, and replication of viral nucleic acid, beginning with transcription. The viral RNA of most plus sense ssRNA viruses binds directly to ribosomes and is translated in full or in part without the need for any prior transcriptional step. For all other classes of viral genomes, mRNA must be transcribed in order to begin...

Viral Diseases

Rational Use of the Laboratory 191 Collection, Packaging, And Transport of Specimens 193 Direct Identification of Virus, Vira Antigen, or Viral Genome 195 Measurement of Serum Antibodies 210 Why bother to establish a definitive laboratory diagnosis ol a viral infection when few effective chemotherapeutic agents are available and many viral diseases are clinically obvious or trivial This is a valid question. The majority of viral infections can be handled without recourse to the laboratory....

O

Vector bitinq arthropod Sandfly fever, dengue Fig- 14-2 Modes of transmission of human viral diseases. Modified from C A. Mims, The Pathogenesis of Infectious Disease, 2nd Ed. Academic Press, London, 1982 hospital or clinic. The lethal Ebola virus outbreaks in Zaire and the Sudan in 1976 were classic examples of iatrogenic nosocomial infections more common examples of nosocomial virus infections are the occurrence of chickenpox, influenza, and respiratory syncytial virus cross-infections in...

Info

5, 8, 9, 12, 14, 15, 17, 19-25, 36, 46, 47 Common types in bold type Types 5, 8, and less commonly 17, 20, and 47 are the principal types so far associated with malignant change in epidermodysplasia verruciformis Common types in bold type Types 5, 8, and less commonly 17, 20, and 47 are the principal types so far associated with malignant change in epidermodysplasia verruciformis cences of soft papillomas found on the external genitalia, perineum, vaginal introitus, penis, or anus, caused...

Families of RNA Viruses

Family Picornaviridae Picorn a viruses Genus Hepatovirus hepatitis A-Iike viruses The Picornavirtdae pica, micro-micro rrn, sigla for ribonucleic acid comprise small nonenveloped icosahedral viruses 25-30 nm in diameter, which contain a single molecule of plus sense ssRNA 7.5-8.5 kb , and replicate in the cytoplasm see Table 2-2 . The genus Enterovirus includes 3 polio-viruses, 32 human echoviruses, 29 coxsackieviruses, and a few other human enteroviruses. Most of these viruses usually produce...

Respiratory Syncytial Virus

Oxygen Tent For Infant 1960s

Respiratory syncytial virus RSV is the most important respiratory pathogen of childhood, being responsible for about half of all cases of bronchiolitis and a quarter of all cases of pneumonia during I he first few months of life. The virus multiplies in the mucous membranes of the nose and throat in the very young and very old it may involve the trachea, bronchi, bronchioles, and alveoli. The incubation period is 4-5 days. Fatal cases usually show extensive bronchiolitis and pneumonitis with...

Hhv6

Types 1 and 2 Varicella virus Adenovmdae All adenoviruses Miiwainntlcie BK, JC polyomaviruses Recurrent excretion in saliva, genital Rrtioviiulnc Human immunodeficiency viruses Ht'i gt aitrm gt irnfae Hepatitis B virus Aiemipirulm' All arenaviruses Togiwirittac Rubella virus secietions, for years Recurs as zoster many years later intermittent excretion from throat and or feces Excreted in urine Persistent viremia, may occur in semen, saliva In rodents, intermittent shedding in urine Persistent...

Principles of Animal Virology

Chapter 1 Structure and Composition of Viruses Viral Morphology 4 Chemical Composition of Virions 10 Preservation of Viral Infectivity 14 Further Reading 15 Chapter 2 Classification and Nomenclature of Viruses Criteria for Viral Classification 16 Nomenclature 17 Families of DNA Viruses 17 Families of RNA Viruses 22 Other Viruses 27 Groupings Based on Epidemiologic Pathogenic Criteria Further Reading 29 The Viral Replication Cycle 31 Attachment 33 Uptake Penetration 35 Uncoating 36 Strategies of...