Viral Infections Flashcards
Varicella Etiology
Double stranded DNA Herpes Virus that enters the respiratory tract. Chicken pox- childhood; Zoster older adults
Types of Varicella
Chicken pox- primary infection (highly infective); Zoster- secondary infection (development not always a/w exposure to chicken pox or zoster)
Other reservoir for the virus
None, circulates exclusively in humans
Transmission of Varicella
respiratory route and requires close contact
Symptoms of Varicella (chicken pox)
A mild prodrome and fever precede vesicular rash (small erythmatous papules) Hall mark of Chicken pox is that lesions at all stages of development are all found together. Complete healing in 10-14 days (establishes life long latent infection)
Sypmtoms of Varicella Zoster
Presents with localized infection /eruption, a long the course of one or more dermatomes, most commonly thoracic or lumbar. Preceded with localized pain. Vesicles coalesce into large, confluent blisters.
Dx of Varicella
chicken pox- clinical dx; zoster- dx is more difficult (culture virus from open vessicle and PCR
Complications of Varicella
sinvolvement of pulmonary veins and nervous system (pneumonia, encephalitis) w/ zoster- G. Barre and Opthalmic keratinitis
Tx of Varicella
Acyclovir (oral), IV if severe
Prevention of Varicella
live attenuated vaccine (~100% preventative of serious disease) Recommended for all over the age of 12 mo.
Transmission of EBV
oropharyngeal secretions of assymptomatic shedders, blood transfusion, bone marrow transplant
Acute infectious mononucleosis
vigorous humoral and cellular immune response to rabildy proliferating EBV infected B cells.
Pathogenesis of mononucleosis
infectious B cells and illness manifestations are the result of vigorous T cell and NK cell inflammatory response
Signs and symptoms of mononucleosis
fever, sore throat and lymphadenopaty (classic triad)
Complications of mononucleosis
acute: splenic rupture, neurologic syndromes and ariway obstruction. chronic: hairy leukoplakia, B cell lymphoma, NK cell lymphoma and sarcomas
Dx of mononucleosis
heterophil antibody agglutination test is 90% positive for primary disease. The monospot test may be negative, especially early in the course of the disease. Titer of IgM antibody to viral capsid antigen is the most sensitive and specific test. Elevated at time of infection, then decreases and IgG rises and persists for life.
Tx for mononucleosis
supportive care, if severe give acyclovir
Antigenic Drift
changes in hemagglutinin and neuraminidase proteins resulting from genetic mutation. Changes structure by genetic mutation
Antigenic Shift
reassortment (exchange of genomic segments with other virus strains)- occurs in influenza A
Strains of influenza that commonly cause human disease
Influenza a and b both cause epidemics; A can cause pandemics
Special surface proteins of influenza
Special surface proteins: hemagglutinins (HA) and Neuramidases (NA);
Signs and symptoms of influenza
abrupt onset of fever, shaking chills, head ache, myalgias, pharyngitis and rinorrhea. Complications: viral pneumonia, superinfection, Reyes syndrom (a/w asprin use)
Dx of Influenza
Predominance of systemic symptoms; Rapid influenza test- sensitivity is variable depending on source and quality of specimen
When to initiate tx for influenza
most effective when administered soon after onset of infection
