Virus 1 Flashcards
viral infections
-obligate intracellular parasites
-consist of DNA and RNA genome surrounded by proteins
-may have outer membrane lipoprotein envelope
-viral nucleic acids encode messenger RNA (mRNA) and proteins necessary for replicating, packaging, and releasing progeny virus from infected cells
morphology (dont need to know physiology)
-many viruses are composed of a nucleic acid core and a capsid -> outer capsid surface mediates contact with uninfected cells plasma membranes
-other viruses are more complex and have an outer phospholipid, cholesterol, glycoprotein, and glycolipid envelope that is derived from virus-modified infected cell membranes
-classification of viruses into orders and families is based on nucleic acid composition, nucleocapsid size and symmetry, and presence or absence of an envelope
-viruses of a single family have similar structures and may be morphologically indistinguishable in electron micrographs
-subclassification into genera depends on similarity in epidemiology, biologic effects, and nucleic acid sequence
-Most viruses have a common name related to their pathologic effects or discovery
-formal species names—name of the host followed by the family or genus of the virus and a number-> International Committee on Taxonomy of Viruses.
-e.g., varicella-zoster virus (VZV) or human herpesvirus 3 (HHV-3) -> confusing
-To deliver its nucleic acid payload to the cell cytoplasm or nucleoplasm, a virus must
overcome barriers posed by the cell’s plasma and cytoplasmic membranes
herpes simplex virus
-1 and 2
-incubation- 2-12 days, average 4
-worldwide
-life long
-primary or recurrent
-primary infections occur when pt is initially infected with either HSV1 or 2 for the first time
-recurrent infections or outbreaks occur when the HSV is reactivated
-recurrent infections occur under stress, tend to be milder than initial infection, heal more quickly, and depending on frequency may benefit from suppressive therapy
-HSV viral shedding can occur without obvious lesions -> people may not realize they are infectious
-lesions appear the same in primary and recurrent
-primary infections often include systemic symptoms like fever, malaise, headache, regional lymphadenopathy
-recurrent outbreaks often have prodromal burning or tingling sensation that precedes the appearance
-begin as papules, progress to vesicles, ulcerations, and crust over and heal without scaring
herpes gladiatorum
-HSV1 transmission via skin to skin or skin to mat contact in wresting
herpes gingivostomatitis
-herpes simplex infection of the mouth and gums, herpes simplex of the finger is known as whitlow
herpes simplex keratitis
-infection of the cornea
HSV clinical diagnosis
-viral culture
-PCR testing
-direct fluorescent antibody (DFA) testing
-IgM/IgG serology
-Tzanck smear- microscopy slide prepared with scarping from an unroofed blister, can be obtained to look for multinucleated giant cells
-Tzanck smears are an outdated mode of testing but are included for historical purposes
HSV treatment
-acyclovir, valacyclovir, or famciclovir can be taken orally to decrease the duration of symptoms, hasten healing, and decrease viral shedding
-dosages and duration of treatment required for episodic recurrences are less than those required for initial episodes
-medication can be prescribed for chronic daily suppression for those with frequent outbreaks
-acyclovir is available for oral, topical, and IV administration
-foscarnet can be used in cases of acyclovir resistance
-IV acyclovir is used in cases of herpes meningitis
varicella zoster virus
-VZV
-incubation- 10-21 days, average 14-16
-worldwide
-chicken pox
-highly contagious
-vaccine preventable
-rash that spread in cephalocaudal (head to toe) progression
-rapidly progresses from macules and papules to vesicles and then scabs
varicella zoster virus signs and symptoms
-primary infection occurs after incubation period (14-16 days)
-initial symptoms include a prodrome of fever and malaise (more common in adults) 1-2 days before onset of rash
-rash is pruritic and first appears on head, chest, and back before spreading to extremities
-lesions rapidly progress from macules and papules to vesicles before scabbing over
-new crops of lesions occur over the next 3-4 days
-most lesions crust over within a week
-scabs remain for about 2 weeks before falling off
-typical to have crops of lesions at various stages -> diagnosed clinically
-tends to be mild illness in young children and causes more severe presentations and complications in adolescents, adults, and immunocompromised
-complications can include secondary bacterial skin infections, pneumonia, encephalitis
-pregnant women can pass infection to fetus or neonate -> congenital varicella syndrome or neonatal varicella
varicella diagnosis and treatment
-clinical dx
-polymerase chain reaction (PCR) testing of blister fluid can be done in pregnant females to diagnose acute infections
-treatment is supportive
-calamine lotion to soothe lesions and make them less itchy
-acyclovir can have some benefit in varicella pneumonia and encephalitis
-vaccines to prevent primary (chickenpox) and reactivation VZV (shingles)
-after single dose of vaccine pts may develop “breakthrough disease” if exposed to a wild strain -> lower grade fever, atypical rash pattern, fewer lesions, less likely to develop complications
-lays latent in dorsal root
epstein barr virus (mononucleosis)
-mono, glandular fever, kissing disease
-caused by epstein barr virus, human herpesvirus 4
-incubation- 4-6 weeks
-worldwide
-primarily of adolescents and young adults
-fever, pharyngitis, lymphadenopathy, extreme fatigue
-transmitted via oral secretions and can shed into saliva for several months after initial infection
-may be spread sexually
-if occurs in early childhood often asymptomatic and subclinical
epstein barr virus signs and symptoms
-mild prodrome of headache, malaise, fatigue may precede classic triad of high fever, pharyngitis, and lymphadenopathy
-extreme fatigue common and may last for months even after other symptoms have resolved
-lymphadenopathy is symmetric and typically involves the posterior cervical chain
-pharyngitis with exudative tonsilitis is common and often mistaken for strep
-if ampicillin or amoxicillin is prescribed for presumed strep -> diffuse maculopapular rash often occurs and hepatitis and splenomegaly are common
-splenic rupture can potentially occur and contact sports should be avoided for at least 3-4 weeks
epstein barr virus diagnosis and treatment
-labs will reveal lymphocytosis with > or equal to 50% lymphocytes on peripheral smear with > or equal to 10% atypical in appearance
-liver enzymes (ALT/AST) are often elevated and self limiting
-heterophile antibodies which will cause a positives monospot test
-IgM and IgG antibody testing can also be obtained as well as EBV DNA polymerase chain reaction (PCR) testing
-clinical presentation with characteristic CBC findings and + monospot are often sufficient to make dx
-treatment is SUPPORTIVE
acute cytomegalovirus (CMV)
-acute cytomegalovirus (CMV) infection can have clinical presentation similar to infectious mono
-in both cases- illnesses are self limiting and treatment is supportive
-IgM and IgG antibodies to CMV can be obtained to distinguish from EBV infection
