Viruses Flashcards
(27 cards)
Human Papillomavirus
Infects basal epithelium, causes uncontrolled cell growth
Cutaneous warts, anogenital warts (condylomata acuminata), papillomaa,cervical cancer
Adenovirus
Lytic and latent infections of the respiratory and gastrointestinal tracts, conjunctivae, corneas
Pharyngitis, ARDS, viral gastroenteritis, infant diarrhea
Herpes Simplex Virus
Lytic, persistent, latent infections
Infection through skin, mucous membranes
Lesions appear, subside, reappear when virus is reactivated
HSV-1: above the waist
HSV-2: below the waist
Oral herpes (coldsores), pharyngitis, keratitis, whitlow, genital herpes, encephalitis, meningitis
Varicella-Zoster Virus
Primary infection; presentation due to secondary viremia
After initial infection, virus remains latent in dorsal root or cranial nerve ganglia
Chicken pox; later, shingles (reactivation of latent infection)
Epstein-Barr Virus
Tropism for B-cells
Illness is a “civil war” between B-cells and T-cells
Infectious mononucleosis:
Classic triad of symptoms-lymphadenopathy, splenomegaly, exudative pharyngitis
Heterophile antibody pos
Can lead to chronic disease
Hairy oral leukoplakia
EBV-inducd lymphoproliferative disease (cancerous conditions)
Cytomegalovirus
Initial infection in epithelial cells
Persistent and latent infections
Usually asymptomatic:
congenital infection;
Mononucleosis syndrome (similar to EBV mono, but usually milder;
heterophile antibody neg);
infection more serious in immunocompromised individuals
Variola Virus
Similar to chicken pox-initial infection leads to nonspecific symptoms, secondary viremia leads to disease presentation
Variola major, variola minor
Body-wide vesicular rash caused by hemorrhage of dermal blood vessels
Vomiting, diarrhea, excessive bleeding
Parvovirus B19
Lytic infection, infects erythroid precursor cells
Fifth disease (slapped cheek syndrome):
Biphasic-Week 1, cessation of RBC production;
week 2, rash
Polyarthritis in adults
Aplastic crisis in persons with chronic hemolytic anemias
Poliovirus
Lytic infection; replicated in intestine, infects skeletal muscle then travels up nerves to brain; damage leads to paralysis
Disease outcomes: Asymptomatic Abortive poliomyelitis Nonparalytic poliomyelitis Aseptic meningitis Paralytic polio Bulbar poliomyelitis Postpolio syndrome can occur later in life
Rhinovirus
URT infection
Infected cells release bradykinin and histamine, leading to symptoms of the common cold
Coronavirus
Infects epithelial cells of URT
Most infections similar to the common cold; can exacerbate pre-existing conditions
SARS-CoV
Norovirus
Virus infects intestinal tract, damages brush border leading to malabsorption
Norwalk disease
Measles virus
Mostly lytic, can persist in brain cells
Initial infection in the RT
Disease presentation due to immune system fighting off infection:
T-cells attack infected cells of small blood vessel epithelium
Measles:
Prodromal symptoms, followed by Koplik spots, then maculopapular rash
Complications include pneumonia, encephalitis (subacute sclerosing panencephalitis-defective measles virus persists in brain; infection in 2yr old or younger, symptoms usually appear around 7yr later)
Parainfluenza viruses (1, 2, and 3)
Lytic infection, initially in URT, sometimes spreads to LRT
Cold-like symptoms to bronchiolitis and pneumonia to croup
Mumps virus
Lytic infection, initially in RT epithelium, moves to parotid gland; later spread to other organs
Symptoms due to inflammatory response (immune-mediated)
Mumps (infectious parotitis): Usually asymptomatic Sudden onset of bilaterally swollen parotid glands, fever Other glands swell later on Can lead to CNS involvement
Respiratory Syncytial Virus
Infection of the RT; cell to cell spread, formation of syncytia (giant cells)
Symptoms due to immune system, leads to formation of mucus plugs in airways
Cold-like symptoms to pneumonia:
URT infection in adults and older children
Bronchiolitis in infants and younger children
Influenza viruses (A and B)
Initially infects URT, spreads to LRT
Targets protective cells of RT (ciliated cells, mucus-producing cells)
Hemagglutinin-viral attachment protein
Neuraminidase-facilitates clearing of mucus allowing access to tissue
Infection leads to desquamation of bronchial, alveolar epithelium
Genetic shift, genetic drift (Flu A only!)
Initially, prodromal symptoms
Standard flu symptoms to follow…
Fever, chills, myalgias, etc.
Symptoms in young children often more severe-bronchiolitis, croup, otitis media, vomiting and abdominal pain, rarely febrile convulsions
Complications include bacterial pneumonia, myositis, Reye syndrome
Progressive infection to LRT can lead to hypoxia, bilateral pneumonia
Rabies virus
Infects nerve endings, travels up nerves to CNS and brain
Virus migrates back down to highly innnervated areas; encephalitis and neuronal degeneration follow
Rabies:
Long incubation period
Prodromal symptoms include fever, malaise, headache, pain, parasthesia at infection site, GI symptoms, fatigue, anorexia
2-10 days following, neurologic symptoms appear, followed by coma, death
Filoviruses
Ebola, Marburg
Infection and rapid replication in immune cells leading to cytokine storm
Extensive necrosis of liver, spleen, lymph nodes, lungs; breakdown of blood vessel endothelium
Hemorrhagic fever:
Flu-like symptoms at first, followed by hemorrhage from multiple sites
Widespread hemorrhage leads to swelling and extremely low blood pressure
Flaviviruses
Arboviruses
Lytic infections; target monocytes/macrophages
Initial symptoms in all cases are generalized flu-like, but later diverge by virus type
VEE, EEE, WEE, SLE, WNV-progress to encephalitis
Yellow fever-hemorrhagic fever; degeneration of liver, kidneys, heart; jaundice due to liver damage
Dengue fever-“breakbone fever” (high fever, headache, rash, back pain, bone pain)
Four subtypes of virus; initial infection leads to above symptoms; later infection by a different subtype leads to production of on-neutralizing antibodies; leads to increased vascular permeability (dengue hemorrhagic fever)
Rubella virus
Not lytic; infects URT initially, spreads to lymph nodes, then to rest of body
Immune complexes likely cause rash similar to measles, arthralgia
German measles:
3-day maculopapular rash
Adult infection usually more serious
Congenital disease most dangerous-can lead to cataracts, mental retardation, deafness in newborns
Human Immunodeficiency Virus
Initial infection at mucosal surface during intercouse
Rapid progression to MALT, later infects CD4 T-cell (kill them)
Acquired Immune Deficiency Syndrome:
Initial symptoms similar to flu or mono
3 months after infection-rash or aseptic meningitis common
Gradual degradation of immune system leads to opportunistic infections (PCP, toxoplasmosis, cryptococcal meningitis, cryptosporidia, etc)
Hepatitis Viruses
All viruses target the liver, but symptomology due to immune cells attacking infected cells
Hepatitis A, E
Infectious hepatitis
Fever, fatigue, nausea, loss of appetite, abdominal pain followed by dark urine, pale stool, jaundice
Virus cleared by immune system (no chronic state)
Higher mortality rate for HEV than HAV
