Viral Infections in Childhood

Question 1

Virion

Answer 1

An entire virus particle, consisting of an outer protein shell called a capsid and an inner core of nucleic acid (either ribonucleic or deoxyribonucleic acid—RNA or DNA)
Nucleic acid
Protein coat (capsid)
+/- envelope

Question 2

Nucleocapsid

Answer 2

Nucleic acid + protein coat

Question 3

Viral nucleic acid

Answer 3

Double stranded DNA
(single stranded DNA in parvovirus)
Single stranded RNA (+ or - polarity)
(double stranded RNA in reoviruses)

Question 4

Viruses as intracellular parasites

Answer 4

Dependent on cells they infect for energy, metabolic intermediates and most enzymes

Question 5

Steps in Viral Life Cycle

Answer 5

Attachment
Entry
Uncoating
Synthesis of Viral Components
Assembly + release

Question 6

Step 1: Viral attachment

Answer 6

Binding sites on the virus
Receptors (+/- co-receptors) on plasma membrane of cell
“cell tropism”
Cell must be permissive (have all the right intracellular components required by the virus to replicate

Question 7

Step 2: Entry

Answer 7

Takes from seconds to several minutes
Enveloped viruses undergo membrane fusion
May undergo receptor-mediated endocytosis

Question 8

Step 3: Uncoating

Answer 8

Can take place in:
–> endosome (receptor mediated endocytosis), due to low pH and lysosomal enzymes
–> cytosol
–> nuclear membrane
Results in transport to right part of cell to begin new virion production

Question 9

Step 4: Synthesis of viral components

Answer 9

Requires viral mRNA to enable viral polypeptides and nucleic acid to be synthesised by cell machinery
DNA viruses that enter the nucleus can use only cellular enzymes
All other viruses must synthesise their viral mRNA
May carry their own enzymes (e.g. RNA polymerase, reverse transcriptase)

Question 10

Step 5: Assembly + release

Answer 10

After synthesis of viral proteins + nucleic acid, virions assembled
Released by cell lysis + budding

Question 11

Important Enveloped DNA viruses

Answer 11

Herpes Viruses
–> herpes simplex, varicella zoster, CMV, Epstein-barr, HHV 6/7/8
Hep B
Poxviruses

Question 12

Important Non-Enveloped DNA viruses

Answer 12

Papillomavirus
Adenovirus
Parvovirus (ssDNA)

Question 13

Disseminated Herpes simplex virus in neonates

Answer 13

Sepsis-like syndrome
Hepatitis, coagulopathy
High mortality
IV aciclovir

Question 14

HSV encephalitis

Answer 14

Fever
Seizures
Haemorrhagic infarction of white matter + cortex

Question 15

Cytomegalovirus

Answer 15

Self-limiting illness

Severe disease in immunosuppressed

Question 16

Congenital CMV

Answer 16

Commonest congenital infection in developed countries

Long term hearing deficit and neuro-developmental delay

Question 17

Congenital CMV Treatment

Answer 17

IV ganciclovir or oral valganciclovir- inhibits DNA synthesis
6 months treatment reduces hearing loss + improves neurodevelopment

Question 18

Chickenpox in adults

Answer 18

Generally more severe than children
Pneumonitis
Particularly severe in pregnant women

Question 19

Epstein-Barr virus

Answer 19

Spread by saliva
Infectious mononucleosis (glandular fever), typically 15-25 years old

Question 20

Burkitt’s lymphoma

Answer 20

Africa

EBV infection at early age

Question 21

EBV impact

Answer 21

Lymphoma in children + adults with advanced HIV disease

Post-transplant lymphoproliferative disease

Question 22

HHV-6 and 7: Roseola infantum

Answer 22

AKA Exanthem subitem
Common 6 months-2yrs
Sudden onset of high fever, lasts few days then stops, rash appears

Question 23

Consequence Hep B Chronic infection

Answer 23

Cirrhosis

Hepatocellular carcinoma

Question 24

Hep B mother to child

Answer 24

Risk of transmission
--> eAg-negative 10-20%
--> eAG-positive 90%
Reduced to <5% with interventions at birth
Vaccine +/- HBIG

Question 25

Molluscum contagiosum

Answer 25

Normal host- moist areas, direct contact, mild but persist several years Immunosuppressed- severe

Question 26

Papillomavirus

Answer 26

Cause of cervical cancer Serotypes 16 + 18 carcinogenic Serotypes 6 + 11 genital wart

Question 27

Papillomavirus vaccines

Answer 27

Cervarix- 16,18 | Gardasil- 6, 11, 16, 18

Question 28

Adenovirus

Answer 28

URTI/pneumonia Conjunctivitis Diarrhoea Disseminated disease in immunocompromised hosts

Question 29

Parvovirus B19

Answer 29

Attaches to blood group P antigen If people lack P antigen, not susceptible Replicates in rapidly dividing cells (red cell precursors)--> in people with haematological problems, leads to aplastic crisis

Question 30

Parvovirus B19 symptoms

Answer 30

``` Asymptomatic "slapped cheek" syndrome Arthropathy Aplastic crisis Foetal loss ```

Question 31

Important Enveloped RNA virus

Answer 31

Measles, mumps, rubella RSV, influenza, parainfluenza Hep C HIV

Question 32

Important non-enveloped RNA virus

Answer 32

Rotavirus Enteroviruses Hep A

Question 33

Measles

Answer 33

``` Fever Cough Conjunctivitis Miserable Koplik spots Rash Subacute sclerosing pan-encephalitis ```

Question 34

Congenital Rubella

Answer 34

Eyes- cataracts, micro-ophthalmia, glaucoma Ears- sensorineural deafness Heart- pulm artery stenosis, VSD Low birth weight, rash, microcephaly

Question 35

Bronchiolitis

Answer 35

``` 70% RSV Inflammation of bronchioles Cough Resp. distress Wheeze Palivizumab (monoclonal Ab) for prevention ```

Question 36

Oral Rotavirus vaccines

Answer 36

RotaTeq | RotaRix