Childhood Viruses Flashcards Preview

IAHI Block 3 > Childhood Viruses > Flashcards

Flashcards in Childhood Viruses Deck (36):
1

Viruses of childhood (causing viremia)

Measles Virus
Mumps Virus
Rubella Virus
Parvovirus B19
Varicella zoster

2

Why are vaccines against Measles, Mumps, and Rubella so effective?

- Natural infection protects against re-infection and disease
- Each virus has only a single antigenic type - key to vaccine effectiveness
- Each virus has a systemic replication phase prior to infecting target organ where symptoms develop - antibodies developed as a result of immunization can limit or block virus at this stage
- Humans are the only known host

3

Cilnical consequences of measles virus infection

Measles - cough, conjunctivitis, coryza, photophobia, Koplik spots
Atypical Measles - more intense rash, petechiae, purpura
Postmeasles encephalitis - acute onset of headache, confusion, vomiting
Subacute sclerosing panencephalitis - CNS manifestations

4

Which complication of the measles virus is the most likely to cause death in children?

Pneumonia

5

Measles, mumps, rubella vaccine (MMR)

Live attenuated viruses given as combination
- 12-15 months and 4-6 years
Induce strong long lasting antibody response - prevents infection of target organ

6

Measles is particularly endemic in ______

Kenya

7

Between 2000 and 2010, measles deaths has decrease __%

74

8

Mumps clinical syndromes

Infections often asymptomatic
Parotitis - almost always bilateral and accompanied by fever
Swelling of other glands
CNS involvement

9

Disease mechanisms of Mumps virus

1) Virus infects epithelial cells of respiratory tract
2) Virus spreads systemically by viremia
3) Infection of parotid gland, testes, and central nervous system
4) Principal symptom is swelling of parotid glands caused by inflammation
5) Cell mediated immunity is essential for control of infection and responsible for causing some of the symptoms - antibody is not sufficient because virus spreads from cell to cell

10

Effective live attenuated vaccine (Mumps)

Humans only host
Only one serotype
Lifelong immunity

11

Rubella German Measles (characteristics)

- Is a togavirus
- Only infects humans
- Has only one serotype
- Does not cause readily detectable cytopathologic effects
- Can cause asymptomatic infections

12

Clinical diseases caused by rubella virus
Children:
Adults:
Neonates younger than 20 weeks:

Children: Mild rash disease
Adults: More severe disease with arthritis or arthralgia
Neonates younger than 20 weeks: congenital defects

13

Prominent Clinical Fingings in Congenital Rubella Syndrome

Cataracts and other ocular defects
Heart defects
Deafness
Intrauterine growth retardation
Failure to thrive

14

Parvovirus B19 (characteristics)

- Singe stranded DNA virus
- Icosahedral, non enveloped
- Replicates in nucleus
- Dependent on host DNA replication functions

15

Bocavirus (Parvovirus)

A newly discovered parvovirus responsible for respiratory and gastrointestinal tract infections

16

Parvovirus B19
Infection:
Receptor:
Replication:

Infection: infects actively replicating red blood cell progenitors in blood marrow
Receptor: Blood group P antigen (globoside) - expressed on mature erythrocytes
Replication: Uses cellular DNA polymerase to replicate

17

Parvovirus time course of infection

0-5 days: Incubation
5-14 days: Lytic, infection phase
21-28 days: Noninfectious immunologic phase

18

Parvovirus B19 clinical features

Usually causes clinically inapparent infection
Clinically apparent disease: Erythema infectiosum (Fifth disease)
- Bright red cheeks
- Maculopapular rash
- Circulating immune complexes, do not fix complement, but cause rash, arthralgia and arthritis

19

Complications of Pavrvovirus B19 infection

Causes anemia due to reduced cell number and reduced hemoglobin
In chronic hemolytic anemia patients virus causes aplastic crisis due to destruction of red cell progenitors
When transmitted to the fetus (ventricle): Can cause still births, generalized edema, anemia, congestive heart failure

20

Rotavirus (Reo) and Norovirus (Calici) Transmission

Fecal oral transmission
Replication in GI tract
Gastroenteritis, Diarrhea, Vomiting

21

Most common cause of severe diarrheal illness requiring hospitalization in infants and young children

Rotavirus

22

Rotavirus - "wheel"
Genome and characteristics

11 double stranded RNA segments encoding 12 genes
No envelope - three layer capsid
Multiple antigenic groups (A-E)
Group A - most common cause of human disease
Great diversity of antigenicity - multiple serotypes
Co-infection can lead to reassortment of segments (mutation rate 1000X higher than DNA viruses)

23

Antigens and proteins on Rotavirus molecule

VP4 neutralization antigen (P serotype - 28)
VP7 neutralization antigen (G serotype - 19)
VP6 subgroup antigen (A-E)
Non-structural proteins (NSPs)
NSP4 - acts as enterotoxin

24

Mechanisms by which rotaviruses cause diarrhea

1) infection of initial cell by luminal virus leads to entry, uncoating, transcription and translation of viral proteins
2) Intracellular NSP4 induces release of Ca2+ from internal stores - primarily the ER increasing internal calcium
3) NSP4 produced by the infection disrupts tight junctions allowing paracellular flow of water and electrolytes
4) Increase in calcium also disrupts the microvillar cytoskeleton - stimulates enteric nervous system which induces Cl- secretion

25

Rotavirus Vaccines
RotaTeq:
Rotarix:

RotaTeq:
- Approved by the FDA in 2006
- Live attenuated vaccine, humans - bovine reassortant, mixture of 5 different virus types
- Given 3 times orally between ages 2, 4 and 6 months
Rotarix:
- Approved by FDA in 2008
- Live attenuated single human strain, based on most prevalent circulating strain globally
- Given 2 times orally at about 2 and 4 months

26

Considerations for Rotavirus Vaccines

- Vaccine related intussusception
- Possible reversion to virulent strain
- Viremia - side effects
- Shedding of virus by vaccine recipients
- Immunosuppressed children

27

Norovirus
Discovery:
Symptoms:

Discovery: Discovered in 1972 in an Ohio outbreak
Symptoms: Major cause of acute gastroenteritis in school-aged children and adults

28

Norovirus illness is most common in ______

Winter

29

Norovirus Epidemiology
Low infectious dose:
Prolonged asymptomatic shedding:
Stability:
Substantial strain diversity:
Lack of lasting immunity:

Low infectious dose: person to person spread, secondary spread
Prolonged asymptomatic shedding: Increased risk for secondary spread regarding food handlers
Stability: Difficult to eliminate from contaminated water - virus maintained in ice and steamed oysters
Substantial strain diversity: Requires composite diagnostics
Lack of lasting immunity: Childhood infection does not protect from disease in adulthood

30

Targets for the design of antiviral therapies (for norovirus)

Pro - viral protease
Pol - viral polymerase (RNA dependent)

31

Enteroviruses

Coxsackie virus
Echovirus

32

Clinical syndromes associated with major enterovirus groups

Paralytic disease
Encephalitis, meningitis
Respiratory tract infections
Undifferentiated fever

33

Which month has the highest incidence of enterovirus cases

August

34

Viral meningitis occurs mostly in children younger than age __

5

35

Meningitis
Common symptoms in infants:
Common symptoms in adults:

Common symptoms in infants:
- fever
- irritability
- poor eating
- hard to awaken
Common symptoms in adults:
- Headache
- fever, chills
- nausea, vomiting
- stiff neck
- sensitivity to light

36

Coxsackie A viruses - Hand foot and mouth disease
Symptoms:

Mild fever
Sore throat
Fatigue
Loss of appetite
Vesicular lesions