Viral Diseases of Childhood Flashcards
the 5 common childhood viral xanthemas (rashes)
measles scarlet fever german measles filatov dukes erythema infectiosum roseola infantum
scarlet fever
organism?
symptoms?
group A strep = strep pyogenes)
sore throat, fever and red rash
german measles
organism?
rubella virus
erythema infectiosum
organism and presentations
parvovirus B19
slapped cheek syndrome
roseola infantum
org?
HSV 6 and 7
paramyxoviruses
large, enveloped negative-stranded RNA (-RNA) viruses with a single-stranded non-segmented RNA genome and their own RNA-dependent RNA polymerase
cause common diseases like respiratory tract infections, measles, mumps and neurological disease
route of transmssion for paramyxoviruses is
respiratory
Paramyxoviruses and the childhood viral infections they cause:
1-respirovirus? 2-morbillivirus? 3-rubulavirus? 4-pneumovirus? 5-metapneumovirus?
1 - parainfluenza virus (PIV types 1 and 3)
2 - measles
3 - mumps and parainfluenza types 2 and 4
4 - RSV (respiratory syncytial virus)
5 - hMPV (human metapneumovirus)
paramyxoviruses have their own what?
RNA dependent RNA polymerase!
paramyxovirus replication
virus is a -RNA
transcription by viral RNA dep RNA polymerase
–transcription complex = L(large)-polymerase protein + NP (nucleoprotein) + P (phosphoprotein)
this creates +RNA template and mRNAs
–mRNAs are translated into proteins and the +RNA template makes more -RNA genomes
proteins and RNA genomes are assembled into new viruses
virus particles undergo “budding” from infected cell
paramyxovirus replication is detected by three ways:
1 - hemadsorption cell fusion (syncytia or giant cells)
2 - immunofluorescence
3 - reverse transcriptase PCR (RT-PCR)
paramyxovirus-specific neutralizing antibodies are reactive to what structures of the virus?
reactive to the F glycoproteins and the attachment glycoproteins (H, HN, and G) on the outer envelope
parainfluenza viruses cause what type of infections?
6 syndromes due to parainfluenza virus?
–> local infections of the respiratory tract
1 - inapparent infection
2 - minor respiratory infection
3 - croup (laryngo-tracheitis)
4 - bronchitis
5 - bronchiolitis (lower airway inflammation)
6 - bronchopneumonia (pneumonia localized to smaller bronchial tubes)
upper resp. infection with barking cough
croup
inflammation and infection of the voice box
are vaccines available for parainfluenza virus?
no
Problems: how to induce long-lasting immunity when natural infection does not, viruses cause disease in early infancy, vaccines must be effective in the presence of maternal antibody
parainfluenza virus types 1/2 vs 3 vs 4
major syndrome?
age?
when?
1/2 –> croup, 6mo to 5 yr, in the autumn
3 –> bronchiolitis/pneumonia, 0-6months, endemic
4 –> URI, kids, endemic
RSV
major syndrome?
age?
when?
bronchiolitis/pneumonia
0-6months
winter epidemic
in immunocompromised patients, parainfluenza viruses and RSV have…
prolonged and severe infection (30% mortality in bone marrow recipients)
RSV
a Pneumovirus (no HA or NA activities)
Has a F (fusion) glycoprotein
The MOST important cause of lower respiratory tract disease in young children. Will infect virtually all infants by age 2.
Symptoms resemble the common cold.
In premature infants or those with chronic lung disease, RSV can cause severe to life-threatening illness.
Restricted to the respiratory epithelium.
Immunity is not long-lived.
There is a prophylactic therapy (passive antibody therapies: (palivizumab (Synagis™).
palivizumab
monoclonal Ab prophylaxis against RSV in infants
what will infect almost all infants by 2?
RSV
mumps
a paramyxovirus systemic infection
–viremia that spreads to parotid glands (parotitis) and other epithelium (testes/ovaries, meninges, thyroid, bladder, kidney, and pancreas)
presents 2-3 weeks after exposure
complications of mumps?
meningitis, orchitis (unilateral), encephalitis
how to acquire mumps immunity?
usually acquired in childhood
infection gives lifelong immunity since there is only one serotype and infection is systemic
or MMR vaccine
who is most at risk for mumps?
post pubertal boys
mumps vaccine
a live-attenuated vaccine (part of MMR with measles and rubella)
measles
paramyxovirus systemic infection
VERY contagious - if child is non-immune = will contract virus
2 week incubation period
infects via respiratory tract –> local replication –> spreads to lymphoid tissue via viremia –> infects skin and organs
symptoms = kopliks spots, fever, cough, conjunctivitis, and rash; photophobia
measles rash depends on…
patients with low CMI….
cell mediated immunity
people with low CMI do NOT develop rash but instead get measles giant cell pneumonia
kopliks spots
clustered little white lesions in mouth near molars that appear a few days before MEASLES rash
3 neurologic complications of measles
acute disseminated encephalomyelitis (ADEM) - within a month after infection
measles inclusion body encephalitis (MIBE) - 1-9 months after infections
subacute sclerosing panencephalitis (SSPE) - 3-12 years after BECAUSE virus persists in neurons (CNS inclusions) causing fatal CNS disease
measles immunity acquired how?
one serotype worldwide so infection gives life immunity
CMI is required to clear the infection
MMR vaccine is a live attenuated virus
or
passive immunity with anti-measles IgG
rubella virus
german measles
a togavirus = small enveloped +RNA virus with single stranded nonsegmented RNA genoma
causes congenital rubella syndrome
MMR vaccine
properties of togaviruses
2 types?
(toga) = enveloped
attaches to host cells with glycoprotein spikes
entry through endocytosis (pH dependent)
viral genome is + sense –> serves as template for protein synthesis
rubella and alphavirus
rubella infection
usually mild
respiratory entry –> spread to lymph nodes –> viremia –> skin and fetus (teratogenic)
symptoms: maculopapular rash (rubelliform), lymphadenopathy, low grade fever, conjunctivitis, sore throat, arthralgia
* *rash is main feature and first sign
can rubella cross placenta?
what happens if 1st timester infection?
yes; teratogenic and causes congenital rubella syndrome
esp 1st trimester infection –> deafness, blindness (cataracts), heart or brain defects
baby continues to shed virus after birth for a few months
complement fixation test for rubella?
known antigen is reacted with an unknown antibody in he patients serum
no lysis = prescence of antibody (positive test)
lysis = lack of specific antibody (negative)
CF titers
- -> acute serum titer is 4
- ->convalescent titer is 32
- *this >4 fold increase in CF titer DOES indicate recent rubella infection
titer of 128 = protextion via pre-existing immunity
what diseases are caused by parvovirus B19?
erythema infectiosum (5th disease, slapped cheek disease)
apastic crisis in people with chronic hemolytic anemia (sickle cell anemia)
hydrops fetalis (anemia and CHF)
polyarthritis
parvovirus B19 infection mechanism
through respiratory droplets or contaminated blood
virus infects mitotically active erythroid precursors; establishes viremia
–can cross into placenta -> fetus
vaccine for parvovirus B19?
no
parvovirus B19 structure
small
icosahedral
nonenveloped
linear, nonsegmented, ssDNA
erythema infectiosum (EI)
5th disease “slapped cheek disease”; caused by parvovirus B19
common in school kids
4-14 day incubation
nonspecific symptoms (infectious during this time) = myalgia/arthritis, fever, headache, malaise, chills
maculopapular rash on face occurs about 18 days after exposure (no longer infectious at this stage)
fetal B19 infection
B19 can cross placenta to infect the fetus causing fetal anemia and congestive heart failure (hydrops fetalis) that lead to spontaneous abortion
B19 infection leads to what crisis?
transient aplastic crisis
B19 infection results in a transient depletion of erythrocyte precursors and a reduction in erythropoiesis, which leads to reticulocytopenia and a decrease in hemoglobin level that lasts for 7-10 days.
The reticulocytopenia can be life-threatening in people with hemolytic anemia (sickle cell anemia).
roseola
6th disease
caused by HHV6 and 7 (human herpes virus)
VZV
chickenpox (primary vzv) and shingles (recurrent vzv)
due to HHV6 and 7
transmitted by aerosol and direct contact
viremia allows spread
differential ddx for: lymphadenopathy, low grade fever, and maculopapular rash
measles scarlett fever roseola (Hhv 6/7) parvovirus b19 rashassociated enteroviruses
***to differentiate, must do lab serology or virus isolation
which enteroviruses can also cause rash
coxsackie A and B and echovirus
LIVE vaccines pros and cons
pros –> mimics natural immunity, humoral and cellular responses, durable immunity, and herd immunity
cons –> reversion to virulence, restricted by prior immunity, spread to contacts
non-living vaccines pros and cons
pros–> not restricted by prior immunity, safe (not infectious), potency can be adjusted easily
cons –> poor CTL response, transient immunity, limited herd immunity
all successful viral vaccines induce ____
neutralizing antibodies
what viral vaccine is recomended at birth?
…yearly?
…at 1 year?
…at 11-12?
Hep B
influenza
MMR, varicella, HepA, IPV (polio)
HPV and tDAP
