Viral Infections

Question 1

Latency

Answer 1

cell infected with a virus that does not interfere with cellular functions - virus can emerge to produce disease years after the primary infection

Question 2

RNA Viruses vs DNA Viruses

Answer 2

• RNA viruses (HIV-1, hepatitis C) have polymerases that do NOT proofread the strand being synthesized
• RNA viruses have a very high mutation rate
• A greater percentage of daughter RNA virions are inactive

Question 3

The common cold

Answer 3

• usually RNA viruses, specifically rhinoviruses or coronaviruses
• stick to respiratory epithelium and reproduce well below 37C (stick to upper airway)
• chemical mediators like bradykinin produce most of the symptoms

Question 4

Influenza virus

Answer 4

Acute infection of upper and lower airways caused by enveloped SS RNA virus

• Influenza A is most common and most severe
• spreads from respiratory droplets and secretions
• enters cell by fusion with cell membrane and causes cell to produce progeny then die
• causes necrosis and desquamation of respiratory epithelium
• rapid onset of fever, chills, myalgia, headaches, weakness, nonproductive cough

Question 5

Parainfluenza virus

Answer 5

• paramyxoviridae (RNA) - enveloped, SS, neg sense
• associated with croup (barking cough with stridor on inspiration)
• cause upper and lower respiratory tract infections, especially in young children
• spread from respiratory aerosols and secretions, highly contagious
• infect and kill respiratory epithelium and ilicit inflammatory response

Question 6

Respiratory Syncytial Virus

Answer 6

• paramyxoviridae (RNA)
• associated with bronchiolitis in infants
• spread via respiratory aerosols and secretions
• viral surface proteins cause binding and fusion to respiratory epithelium
• produce necrosis and sloughing of epithelium with lymphocytic inflammatory infiltrate
• sometimes can see multinucleated syncytial cells
• symptoms of wheezing, cough, respiratory distress

Question 7

Severe Acute Respiratory Syndrome (SARS)

Answer 7

• coronavirus (RNA)
• incubation period of 2-7 days
• causes diffuse alveolar damage and multinucleated syncytial cells without viral inclusions
• fever and headache followed by cough and dyspnea
• lymphopenia and elevated aminotransferase levels present
• can develop ARDS

Question 8

Measles (Rubeola) - RASH

Answer 8

• enveloped, single-stranded RNA virus
• upper respiratory symptoms, fever, and rash
• spread via respiratory aerosols and secretions
• viral surface glycoproteins (H and F) mediate attachment and fusion in epithelium, which then spreads to lymph nodes and bloodstream
• rash from action of T lymphocytes on virally infected vascular endothelium
• necrosis of resp epithelium with lymphocytic inflammatory infiltrate
• Warthin-Finkeldey giant cells are fused infected cells that contain up to 100 nuclei - diagnostic
• fever, rhinorrhea, cough, and conjunctivitis –> mucosal or skin lesions
• Koplik spots/mucosal lesions - gray-white dots on a red base that occur in back of cheek
• Skin lesions - begin on face and spread to trunk and extremities - erythematous macropapular rash
• acute encephalitis can occur

Question 9

Rubella - RASH

Answer 9

• enveloped, single stranded RNA
• associated with congenital anomolies in utero (deafness, cataracts, glaucoma, heart defects, mental retardation)
• spread via respiratory route
• respiratory epithelium to bloodstream and lymphatics
• rash from immunologic response
• rhinorrhea, conjunctivitis, postauricular lymphadenopathy with rash

Question 10

Mumps

Answer 10

• enveloped, single stranded RNA
• characterized by parotid gland swelling and meningoencephalitis
• spread via respiratory route
• enters via respiratory epithelium, disseminates in blood and lymph to salivary glands, CNS, pancreas, and testes
• necrosis of infected cells with lymphocytic inflammatory infiltrate
• fever and malaise to painful swelling of salivary glands

Question 11

Rotavirus - GI

Answer 11

• most common cause of severe diarrhea worldwide
• DS RNA virus
• spread via oral-fecal route
• infects enterocytes of upper small intestine, disrupting absorption of sugars, fats, and various ions
• osmotic load causes water rush to lumen, and infected cells are shed - new cells lack full absorptive capability
• duodenum and jejunum - shortening of villi and mild infiltrate of neutrophils and lymphocytes
• vomiting, fever, pain, profuse watery diarrhea

Question 12

Norwalk Virus - GI

Answer 12

• nonenveloped RNA calicivirus
• produce gastroenteritis
• changes similar to rotavirus

Question 13

Families of viral hemorrhagic disease and epidemiologic groups

Answer 13

Bunyaviridae
Flaviviridae - enveloped, SS RNA
Arenaviridae
Filoviridae

mosquito-borne
tick borne
zoonotic
filoviruses (ROT unknown)

Question 14

Yellow Fever - HEMORRHAGIC

Answer 14

• may lead to fulminant hepatic failure
• caused by Aedes mosquito borne flavivirus
• enveloped SS RNA
• virus multiples within tissue and vascular endothelium then through bloodstream
• attracted to liver cells
• can lead to loss of vascular integrity, hemorrhages, and shock
• causes coagulative necrosis of hepatocytes
• Councilman bodies - apoptotic cells
• abrupt onset fever, chills, headache, myalgias, nausea, vomiting, jaundice, loss of clotting factors, bleeding, vomiting blood

Question 15

Ebola virus - HEMORRHAGIC

Answer 15

• fruit bat carried RNA filoviridae
• most severely widespread destructive tissue lesions
• virus replicates in endothelial cells, mononuclear phagocytes, hepatocytes and cause necrosis in liver, kidneys, gonads, spleen, lymph
• Liver shows Kupffer cell hyperplasia, Councilman bodies, microsteatosis
• shock
• incubates 2-21 days with headache, weakness and fever followed by diarrhea, nausea, vomiting

Question 16

West Nile Virus - HEMORRHAGIC

Answer 16

• spread via mosquitos and birds
• RNA flaviviridae
• slightly increased sedimentation rate and mild leukocytosis, varying degress of neuronal degeneration and necrosis
• fever with rash lymphadenopathy and polyarthropathy can develop to aseptic meningitis or encephalitis

Question 17

Adenovirus

Answer 17

• nonenveloped DNA
• acute respiratory disease
• necrotizing bronchitis, interstitial pneumonitis

Question 18

Human Parvovirus B19

Answer 18

• SS DNA
• erythema infectiosum - benign febrile illness in kids, interruption of erythropoiesis
• respiratory spread
• in those with anemia, interruption of RBC can be fatal –> TRANSIENT APLASTIC CRISIS

Question 19

Smallpox

Answer 19

• DNA virus of variola of Poxviridae family
• characteristic rash most prominent on face
• lesions from macules to papules to pustular vesicles

Question 20

Monkeypox

Answer 20

• DNA virus from Poxviridae family

- similar to smallpox but milder

Question 21

Varicella-Zoster

Answer 21

• enveloped DNA Herpesvirus
• first exposure –> chickenpox
• latency and reactivation –> shingles (DRG to one dermatome)
• upper layers of epidermis separate from basal layer to form vesicles

Question 22

Herpes Simplex Viruses

Answer 22

• enveloped DNA
  HSV-1: oral secretions, disease above waist
  HSV-2: genital secretions, disease below waist
• primary infection forms vesicles
• secondary infection may produce vesicles or just shed contagious progeny
• TX: acyclovir

Question 23

Epstein-Barr Virus

Answer 23

• enveloped DNA, herpesvirus
• infectious mononucleosis, Burkitt lymphoma, B-cell lymphoma, nasopharyngeal carcinoma
• polyclonal activator of B cells

Question 24

Cytomegalovirus

Answer 24

• enveloped DNA, herpesvirus

- opportunistic - relevant to fetus or immunocompromised patients

Question 25

Human Papillomavirus

Answer 25

• non enveloped DS DNA herpesvirus
• causes proliferative lesions of squamous epithelium
• Types 1, 2, 4 - warts and plantar warts
• 6, 10, 11, 40 - 45 - anogenital warts
• 16, 18, 31 - squamous carcinomas of female genital tract