Microbiology-Viral Diseases of Childhood

Question 1

Viral maculopapular rashes

Answer 1

Measles, rubella, echovirus, coxsackievirus, adenovirus, parvovirus B19.

Question 2

Vesicular/papular viral rashes

Answer 2

Varicella, smallpox, molluscum contagiosum, herpes simplex virus, Coxsackievirus group A

Question 3

Viral petechial/purpuric rashes

Answer 3

Coxsackievirus group A and echovirus

Question 4

Where does influenza replicate?

Answer 4

Orthomyxoviruses replicate in the nucleus, despite being an RNA virus

Question 5

Virus with a large, enveloped, -ssRNA with a non-segmented genome that replicates in the cytoplasm.

Answer 5

Paramyxoviruses: parainfluenza (PIV types 1 & 3), measles virus, mumps virus, human PIV types 2, 4a and 4b, RSV and hMPV.

Question 6

How does infection by paramyxovirus occur?

Answer 6

Capsule glycoproteins bind target cell -> -ssRNA genome transcribed by viral RNA-dependent RNA polymerase to form +ssRNA (then goes to more -ssRNA) and mRNA -> Protein translation from mRNA -> Formation of new viral particles -> Budding out of cell membrane

Question 7

What makes up the different glycoproteins on the outside of a cell infected by measles virus?

Answer 7

Fusion protein and hemagglutinin protein. These glycoproteins are what are responsible for formation of the syncytium.

Question 8

How does the lab detect infection by paramyxovirus?

Answer 8

Isolation from body secretions -> inoculation of human cells in culture -> viral replication detected by hemadsorption cell fusion (forms giant cells or syncytia), immunofluorescence or reverse transcriptase PCR.

Question 9

How do we detect the immune response status of a patient infected by paramyxovirus?

Answer 9

Complement Fixation. Hemagglutination Inhibition. Hemadsorption Inhibition. Virus Neutralization.

Question 10

Types of glycoproteins present on paramyxoviruses that will react with neutralizing antibodies.

Answer 10

F (fusion protein that fuses the virus membrane to the cell membrane), H (hemagglutinin), HN (hemagglutinin and neuraminidase, which cleaves sialic acid) and G (glycoproteins).

Question 11

Syndromes associated with parainfluenza virus

Answer 11

All symptoms are confined to the respiratory tract: minor respiratory infection -> Croup (laryngo-tracheitis) -> Bronchitis -> Bronchiolitis -> Bronchopneumonia

Question 12

Why do kids repeatedly get parainfluenza virus?

Answer 12

Secretory IgA is what develops against parainfluenza viruses because you do not get viremia. This type of immunity is not long-lived.

Question 13

A bunch of kids 6 months old to 5 years old present to the hospital with croup in the fall months. What is the most likely paramyxovirus?

Answer 13

Parainfluenza virus types 1 and 2

Question 14

A bunch of kids present within the 1st 6 months of life with bronchiolitis and pneumonia during all months of the year. What is the most likely paramyxovirus?

Answer 14

Parainfluenza virus 3

Question 15

A bunch of kids present with upper respiratory infections during all months of the year. What is the most likely paramyxovirus?

Answer 15

Parainfluenza virus 4.

Question 16

A bunch of kids present in the first six months of life with bronchiolitis and pneumonia as a part of an ongoing winter epidemic. What is the mod likely paramyxovirus?

Answer 16

RSV

Question 17

What is the target for the only antibody therapy approved by the FDA for prophylactic use against RSV?

Answer 17

F (fusion) glycoprotein is the target of palivizumab (Synagis). Since it is a pneumovirus, it does not have hemagglutinin or neuraminidase activity.

Question 18

What is the course of mumps infection?

Answer 18

Initial respiratory tract infection -> Viremia -> Epithelial cells infected in the parotid, tests, ovaries, pancreas, meninges, thyroid, bladder and kidney -> Orchitis, aseptic meningitis or post-infectious encephalitis.

Question 19

Why does infection confer lifelong immunity in people affected by mumps and measles?

Answer 19

There is only one serotype worldwide and viremia develops IgG response.

Question 20

What type of vaccine is MMR?

Answer 20

Live-attenuated

Question 21

What are the major sequelae associate with mumps infection?

Answer 21

Aseptic meningitis, encephalitis, deafness, orchitis and parotitis.

Question 22

What is the course of measles infection?

Answer 22

Initial respiratory tract infection -> Viremia -> Target organs -> Fever + Koplik spots -> Maculopapular rash (skin is last to be infected and rash is caused by CD8 T-cell response to infected epithelial cells)

Question 23

When will a patient not get the maculopapular rash associated with measles?

Answer 23

If they are immunocompromised, particularly in their ability to have a CD8+ T-cell response because these are what cause the rash.

Question 24

Sequelae from measles infection

Answer 24

2-4 weeks = Acute Disseminated Encephalomyelitis (ADEM). 1-12 months = Measles Inclusion Body Encephalitis (MIBE, typically in immunocompromised). 1-12 years = Subacute Sclerosing Panecephalopathy (SSPE, chronic demyelinating syndrome)

Question 25

Lab diagnosis of someone with measles who was immunocompromised? How do you protect these people from infection?

Answer 25

Measles giant cell pneumonia w/syncytia. You can give passive IgG to protect these people.

Question 26

This virus is a small, enveloped, +ssRNA virus with a non-segmented genome that is a very serious gestation infection with dire consequences for the fetus.

Answer 26

Rubella virus (German measles), which is a Togavirus

Question 27

How does infection by rubella virus occur?

Answer 27

Respiratory epithelium -> Glycoproteins attach to host cell -> Enveloped virus endocytosis -> low pH of endosome releases +ssRNA -> translation begins -> Viremia w/lymph node spread -> skin and fetal spread across placenta (Congenital Rubella Syndrome)

Question 28

In many cases, infection with rubella is mild and asymptomatic. How does clinically apparent rubella present?

Answer 28

Maculopapular (rubelliform) rash forms in 95% of cases, lymphadenopathy, fever, conjunctivitis, sore throat and arthralgia.

Question 29

Why do you need to be extra careful when you have a baby that was born with Congenital Rubella Syndrome?

Answer 29

They can shed the virus for months to years and infect other mothers

Question 30

Major sequelae of Congenital Rubella Syndrome?

Answer 30

Deafness, blindness, cataracts, heart and brain defects.

Question 31

Why is the rubella vaccine unique?

Answer 31

It does not benefit the recipient, it is given to prevent congenital rubella syndrome. In the host the vaccine can cause arthritis.

Question 32

How do you confirm congenital rubella infection?

Answer 32

Complement fixation test: presence of antibody to rubella fixates complement and the red blood cells from the patient do not lyse (form a red dot), this is a positive test. If red blood cells lyse, this means there is no antibody to bind complement and the test is negative. You do this with RBCs from the acute and convalescent stages.

Question 33

How do you treat a pregnant woman who may have been exposed to rubella?

Answer 33

You never give a live attenuated vaccine to a pregnant woman because they are immunosuppressed.

Question 34

Neutralizing antibodies against influenza virus most likely react to which viral proteins?

Answer 34

Hemagglutinin

Question 35

What is oseltamivir (tamiflu)?

Answer 35

It prevents virus release from the host cell by inhibiting neuraminidase.

Question 36

Viral characteristics of a child with a slapped cheek appearance

Answer 36

Parvovirus B19 is a small, non-enveloped, icosahedral DNA virus.

Question 37

What diseases are associated with parvovirus B19?

Answer 37

Erythema infectiosum, aplastic crisis, hydrops fetalis (can cross placenta) and polyarthritis are all results of the viral infection of erythroid precursors.

Question 38

When are kids with parvovirus B19 infection most infectious?

Answer 38

BEFORE the rash appears

Question 39

Disease that is ubiquitous in the population and causes serious infections in immunocompromised patients, but a rash in normal people.

Answer 39

Roseola: HHV-6 and HHV-7

Question 40

What viral disease presents with a variable maculopapular rash?

Answer 40

Enteroviruses (polio, coxsackie and echovirus)

Question 41

A patient presents with lymphadenopathy, low-grade fever and a maculopapular rash. What is your differential diagnosis?

Answer 41

Rubella, measles, scarlet fever, roseola, parvovirus B19 and rash-associated enteroviruses.