RNA Viruses

Question 1

Rubella (German Measels)

Answer 1

Epidemiology: Spreads by respiratory route. World wide locus. Not highly contagious (only 10-15% unvaccinated women remain susceptible into reproductive years). live attenuated viral vaccine prevents rubella.
Pathology: Infects repiratory epithelium and spreads to bloodstream and lymphatics. Rash results from immunologic response to virus and resolves in 3 days. Fetal infection occurs through placenta during viremic phase of maternal illness. Fetus remains persistently infected. Heart, brain, eyes most frequently affected in fetus.
Clinical Features: Febrile illness, rhinorrhea, conjunctivitis, postauricular lymphadenopathy. 30% infections asymptomatic. Fetus: pulmonary valvular stenosis, pulmonary artery hypoplasia, ventricular septal defects, and patent ductus arteriosus. Cataracts, glaucoma, and retinal defects. Microcephally and mental retardation

Question 2

Rubeola (Measels)

Answer 2

• Spread via respiratory tract and secretions (person-person) -Necrosis of respiratory epithelium, with predominate lymphocytic infiltrate.
• Warthin-Finkeldey giant cells (up to 100 nuclei).
• fever, rhinorrhea, cough, and conjunctivitis. -Progresses to characteristic mucosal and skin lesions (Koplik spots) develope -Subacute sclerosing panencephalitis (SSPE) -more deadly in immunocompromised

Question 3

Severe Acute Respiratory Syndrome (SARS)

Answer 3

• SARS-associated coronavirus (SARS-CoV) from bats.
• aerosol respiratory spread -alveolar damage (multinucleate cells without viral inclusions) -fever, headache, cough, dyspnea + some liver involvement (rare)
• higher fatality in elderly

Question 4

Respiratory syncytial Virus (Paramyxoviridae)

Answer 4

• Epidemiology: Belongs to same family as influenza. Spreads rapidly from child to child in aerosols and secretions–daycare centers, hospitals and other areas with confined children.
• Pathology: Viral surface proteins interact with receptors on host respiratory epithelium-viral binding and fusion. Causes necrosis and sloughing off of bronchial, bronchiolar, and alveolar epithelium. Multinucleated syncytial cells seen.
• Clinical Features: Young children with RSV bronchiolitis or pneumonitis have wheezing, cough, and respiratory distress. Illness self-limited (1-2 weeks duration). older adults produces much more mild illness. 20-40% mortality among hospitalized children with congenital heart disease.

Question 5

Influenza Type A, B, C

Answer 5

• Epidemeology: 10-40 million annual cases for 35,000 deaths. Highly contagious and epidemics spread world wide. Hemagluttinin (H) and Neuraminidase (N) designate serotype.
• Pathology: Necrosis and desquamination of ciliated respiratory tract epithelium–lymphocytic infiltrate. infection of lungs leads to necrosis and sloughing of alveolar lining cells.
• Clinical Features: Rapid onset of fever, chills, myalgia, headaches, weakness and nonproductive cough. Upper respiratory infection Deaths from both influenza and its complications. Vaccine 75% effective in preventing influenza.

Question 6

Rotavirus

Answer 6

• Epidemiology: spreads by oral-fecal route. Most common amongst children. siblings, parents, playmates, food, water, and surfaces face contamination. 6 months to 2 years is peak age of infection. (all infected by age 4). 100 deaths in young children in US. 1 million deaths worldwide.
• Pathology: confined to duodenum and jejunem, where there is shortening of intestinal villi and mild infiltrate of neutrophils and lymphocytes
• Clinical Features: Vomiting (2-3 days duration), fever, abdominal pain, and profuse watery diarrhea (5-8 days duration). Without fluid replacement, diarrhea can produce fatal dehydration in young children.

Question 7

Parainfluenza Virus

Answer 7

-Epidemiology: Common in children under 3 years. Spread from person to person through respiratory aerosols and secretions. Highly contagious. Isolated from 10% of young children with acute respiratory tract illness.
-CROUP Pathology: Infect and kill ciliated respiratory epithelial cells and cause inflammatory response. Extends to lower respiratory tract in young children causing bronchiolitis and pneumonitis.
Clinical Features: Local edema of laryngotracheitis compresses upper airway to obstruct breathing and cause croup (laryngotracheobronchitis causing inspiratory stridor and barking cough). Causes fever, hoarseness, and cough. Symptoms mild in adults.

Question 8

Yellow Fever

Answer 8

• mosquito vector (South America + Africa) flavivirus -coagulative necrosis of hepatocytes
• Presence of apoptotic (Councilman) bodies in liver biopsies.
• abrupt onset of fever, chills, headache, myalgias, nausea, and vomiting.
• 3-5 days, hepatic failure with jaundice, clotting factor deficiencies, and diffuse hemorrhages.
• “Black vomit” is classic feature of severe cases.
• High mortality rate

Question 9

Mumps

Answer 9

• Epidemiology: Present worldwide–disease of childhood. Highly contagious–infects 90% of exposed with 60-70% showing symptoms. Live attenuated viral vaccine prevents mumps.
• Pathology: Viral infection of respiratory epithelium–necrosis. Disseminates through blood and lymphatic systems to salivary and parotid glands, CNS, pancreas, and testes. 50% cases involve CNS. Epididymoorchitis (unilateral; no sterility) present in 30% males (swollen to three times normal size)–causing local infarctions. Swollen glands and ducts lined by necrotic epithelium and interstitium infiltrated by lymphocytes.
• Clinical Features: Fever and malaise followed by painful swelling of salivary glands, one or both of parotids. Symptomatic meningeal involvement manifests as headache, stiff neck, and vomiting. Prior to vaccination, mumps was leading cause of viral meningitis. Patients exhibit elevated serum amylase levels though sever pacreatitis is rare.

Question 10

Ebola Virus (Filoviridae)

Answer 10

• Epidemiology: First emerged in Africa, Zaire and Sudan in 1976. Outbreaks caused by Ebola Zaire and Sudan strains primarily. Outbreaks occured in Gabon, Republic of Congo, and Uganda. Fatality rate 53 to 89%. January 2008–Ebola Bundibugyo strain emerged in Uganda. Fruit bats are reservoir for virus. Virus can be spread by bodily secretions, blood, and used needles.
• Pathology: widespread destructive tissue lesions–most damage of all viral hemorrhagic fever agents. Replicates in endothelial cells, mononuclear phagocytes, and hepatocytes. Necrosis is most severe in liver, kidneys, gonads, spleen, and lymph nodes. Hepatocellular necrosis + Kupffer cell hyperplasia, Councilman bodies, and microsteatosis seen in liver biopsies. Lungs hemorrhagic and petechial hemorrhages seen in skin, mucous membranes, and internal organs. Injury to microvasculature–increase vascular permeability leads to shock.
• Clinical Features: incubation time is 2 to 21 days. Initial symptoms headache, weakness, and fever, followed by diarrhea, nausea, and vomiting. Severe disease characterized by overt hemorrhage including bleeding from injection sites, petechia, GI bleeding, and gingival hemorrhage.

Question 11

West Nile Virus (Flaviviridae)

Answer 11

• CSF with leukocytosis,CSF is clear with mild pleocytosis and elevated protein in CNS infection.
• meningoencephalitis (Medulla).
• Fever, Rash, lymphadenopathy, and polyarthropathy.
• not very infectious, but severe disease has moderate mortality