Common Viral Pathogens III

Question 1

Understand the importance of T-cell mediated immunity to VZV infection

Answer 1

There is evidence that lowered cell-mediated immunity to varicella is the critical piece that puts people at risk for shingles. The fact that shingles is more common in the elderly may reflect declining cell mediated immunity in old age. Declining cell-mediated immunity may also be due to fewer exposures to naturally occurring chickenpox in the community (now that most children are vaccinated). Routine exposures used to serve to “boost immunity” in persons regularly

Question 2

Explain the consequences of maternal herpesvirus infection during pregnancy including the risk of the infant developing neonatal HSV

Answer 2

Neonatal herpes is a primary infection of the neonate that can be acquired intrauterine (in utero), peripartum (perinatal) or postpartum (postnatal). The majority of transmissions occur during the peripartum period, e.g. during birth from exposure to maternal secretions with HSV 1 or 2 present (active lesions or asymptomatic viral shedding). Since most genital herpes lesions are caused by HSV-2, most (but not all) neonatal HSV is caused by HSV-2. Because maternal infections can be asymptomatic and because asymptomatic viral shedding can occur, neonatal herpes frequently is diagnosed in babies whose mothers have no history of a known herpes infection. There are three forms of disease: 1) skin, eye and mucous membrane (SEM), 2) CNS, and 3) disseminated, with disseminated being the most severe

Question 3

Explain the consequences of maternal herpesvirus infection during pregnancy including the risk of the infant developing congenital VZV syndrome

Answer 3

• Congenital varicella syndrome—Rare disorder that occurs when varicella is contracted by a pregnant woman in her first 8-20 weeks of pregnancy. The fetus can exhibit multiple tissue and organ abnormalities, such as microcephaly, mental retardation, hypoplasia of extremities, microphthalmia and hypopigmentation.

Question 4

Explain the consequences of maternal herpesvirus infection during pregnancy including the risk of the infant developing CMV syndrome (intrauterine)

Answer 4

When a pregnant woman develops a primary CMV infection, there is a 3-5% chance that the child will be born with a congenital CMV infection. Primary infection in the mother leads to viremia and possible transplacental infection of the fetus. Two thirds of the infants whose mothers contract primary CMV during pregnancy will NOT be infected in utero—1/3 are infected. Fortunately, most of those infected will be asymptomatic. Only 10-15% of the infected infants will have symptoms at birth –this is about 3-5% of the infants born to mothers with primary infections. These babies have congenital CMV. Infection of the fetus can also occur if a pregnant women reactivates CMV, but the risk is much lower (<1% of babies will become infected and even fewer are symptomatic).

Question 5

Explain the consequences of maternal herpesvirus infection during pregnancy including the risk of the infant developing CMV syndrome (perinatally)

Answer 5

CMV may also be transmitted perinatally. Travel through the birth canal may result in infection by aspiration of CMV infected cervical/vaginal secretions. Or the infant may be infected by breastfeeding. More than 50% of infants fed with breast milk that contains infectious virus become infected with CMV. Infants that are infected during the birth process or after delivery (breast milk) do not have the congenital CMV syndrome. These infants usually have asymptomatic infection

Question 6

Know and be able to recognize how CMV can be diagnosed histologically in infected tissues

Answer 6

• characteristic “owl’s eye” appearance, which is diagnostic for CMV infection. The owl’s eye is a dense, dark nuclear body surrounded by a halo. These represent intranuclear inclusions (accumulation of viral proteins or virions).
• There may also be smaller intracytoplasmic inclusions noted

Question 7

CMV serology tests: Positive IgM, negative IgG =

Answer 7

acute CMV disease

Question 8

CMV serology tests: Negative IgM, negative IgG=

Answer 8

patient has never been infected with CMV

Question 9

CMV serology tests: Negative IgM, positive IgG=

Answer 9

patient has previously been infected with CMV at some time in their life

Question 10

CMV serology tests: Positive IgM, positive IgG=

Answer 10

recent CMV reactivation

Question 11

Describe the Chickenpox vaccine

Answer 11

Live attenuated zoster virus vaccine

• initial dose at 12-15 mos of age
• booster at 4-6 years
• DO NOT give to immunocompromised

Question 12

Describe the Shingles vaccine

Answer 12

• Zostavax
• live attenuated vaccine as 1 dose
• 50+
• “boosts” the immune response to VZV and decreases likelihood of developing shingles