Viruses

Question 1

Human Papillomavirus

Answer 1

Infects basal epithelium, causes uncontrolled cell growth

Cutaneous warts, anogenital warts (condylomata acuminata), papillomaa,cervical cancer

Question 2

Adenovirus

Answer 2

Lytic and latent infections of the respiratory and gastrointestinal tracts, conjunctivae, corneas

Pharyngitis, ARDS, viral gastroenteritis, infant diarrhea

Question 3

Herpes Simplex Virus

Answer 3

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

Question 4

Varicella-Zoster Virus

Answer 4

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)

Question 5

Epstein-Barr Virus

Answer 5

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)

Question 6

Cytomegalovirus

Answer 6

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

Question 7

Variola Virus

Answer 7

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

Question 8

Parvovirus B19

Answer 8

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

Question 9

Poliovirus

Answer 9

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

Question 10

Rhinovirus

Answer 10

URT infection

Infected cells release bradykinin and histamine, leading to symptoms of the common cold

Question 11

Coronavirus

Answer 11

Infects epithelial cells of URT
Most infections similar to the common cold; can exacerbate pre-existing conditions
SARS-CoV

Question 12

Norovirus

Answer 12

Virus infects intestinal tract, damages brush border leading to malabsorption
Norwalk disease

Question 13

Measles virus

Answer 13

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)

Question 14

Parainfluenza viruses (1, 2, and 3)

Answer 14

Lytic infection, initially in URT, sometimes spreads to LRT

Cold-like symptoms to bronchiolitis and pneumonia to croup

Question 15

Mumps virus

Answer 15

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

Question 16

Respiratory Syncytial Virus

Answer 16

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

Question 17

Influenza viruses (A and B)

Answer 17

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

Question 18

Rabies virus

Answer 18

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

Question 19

Filoviruses

Answer 19

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

Question 20

Flaviviruses

Answer 20

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)

Question 21

Rubella virus

Answer 21

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

Question 22

Human Immunodeficiency Virus

Answer 22

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)

Question 23

Hepatitis Viruses

Answer 23

All viruses target the liver, but symptomology due to immune cells attacking infected cells

Question 24

Hepatitis A, E

Answer 24

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

Question 25

Hepatitis B

Answer 25

Longer incubation than HAV, HEV
Initial symptoms similar to HAV, HEV
Can lead to fulminant hepatitis (more severe symptoms)
Can lead to chronic disease-virus persist in liver (not cleared by immune system); continued immune cell attack of infected liver cells leading to scarring, cirrhosis, liver failure, primary hepatocellular carcinoma

Question 26

Hepatitis C, G

Answer 26

Similar pathogenic process as HBV
Acute disease-similar to HAV, HBV but milder symptoms
70% of infections are persistent, leading to chronic infection later in life, with similar disease symptoms as chronic HBV disease

Question 27

Hepatitis D

Answer 27

The “delta agent”; cannot cause infection on its own, but rather only if person is already infect with HBV

Active HBV infection+delta agent=coinfection

Chronic HBV infection+delta agent=superinfection
Leads to rapid, serious disease progression
Damage to liver due to cytopathic effect
Fulminant hepatitis common in superinfection