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Flashcards in Paediatric Infectious Disease Deck (41)
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1

Rubella virology: family, type of virus, enveloped v not, hosts, where does replication occur, genome

Togavirus family, rubivurs genus
Small, enveloped +ss RNA (encodes 3 proteins)
Humans are only natural host
Viral replication occurs in the cytoplasm

2

Incubation period and infectious period of rubella

14-18 day incubation period
Are infectious from 1-2 weeks prior to clinically apparent infection, and should be isolated for 7 days after the onset of the rash (Viral shedding reduces with appearance of the rash)

3

Clinical features of rubella

Acute onset of rash:
- pinpoint maculopapular
- PINK (not red like measles)
- First on face - rapid caudal spread over 24 hours
- Evident for approx 3 days
Lymphadenopathy (post-auricular, suboccipital, posterior cervical)
+/- low-grade fever
Mild nonexudative conjunctivitis
Forchheimer spots on soft palate
Arthralgia (more common in teens/adults)

4

Congenital rubella syndrome

Most likely if maternal rubella infection in first trimester of pregnancy
Hearing loss
Mental retardation
Cardiovascular defects
Ocular defects

5

Diganosis of rubella

Rubella serology (IgM and IgG)
Viral isolation from nasopharyngeal secretions
Viral isolation from cord blood or placenta in neonate
Foetal infection diagnosed by CVS

6

Rubella vaccination

Live attenuated
Recommended at 12 & 18 months
Contraindications: pregnancy, immunocompromised

7

Management of rubella

Paracetamol for supportive relief of symptoms
No specific therapy
Offer termination of pregnancy esp. if prior to 16 weeks GA
Droplet precautions
Isolation for 7 days after onset of rash

8

Epidemiology of pertussis

The least well controlled of all vaccine-preventable disease
Epidemics occur every 3-4 years
Maximum risk of infection and severe morbidity is before infants are old enough to have received at least 2 vaccine doses (4 months)
Parents are the source for more than 50% of cases

9

Microbiology of pertussis

Bordatella pertussis
fastidious Gram-negative, pleomorphic bacillus
spreads by aerosols to 90% of susceptible household contacts
Natural infection does not provide long-term protection and repeat infection can occur

10

Diagnosis of pertussis

Clinical diagnosis
Catarrhal stage:
- mild cough and coryza - NASAL DISCHARGE REMAINS WATERY
- cough gradually increases for 1-2 weeks
Paroxysmal stage:
- Paroxysmal coughing spells increasing in severity with inspiratory whoop. May gag or develop cyanosis
- Post-tussive vomiting
- lasts 2-8 weeks
Convalescent stage: cough subsides over weeks to months (median duration of cough - 100 days)

11

Lab investigations in pertussis

Not necessary for diagnosis
WCC usually high with lymphocytosis
B pertussis culture (more difficult after paroxysmal stage has begun)
PCR or serology also options

12

Complications of pertussis

Apnoea
Pneumonia (most common cause of death)
Weight loss secondary to feeding difficulties and post-tussive vomiting
Seizures and encephalopathy

13

Management of pertussis

Supportive care
Hospitalise if: unable to feed, cyanotic, apnoea, seizures, increased work of breathing, concerned for rapid deterioration
Bronchodilators, steroids and antitussive agents are not beneficial
Antibiotic therapy (macrolides e.g. erythromycin) shortens duration and reduces transmission
Droplet precaution until 5 days of effective therapy or 3 weeks after onset of symptoms if untreated

14

Prevention of pertussis

For protection of children under 3 months:
- direct protection by immunisation of mother in last trimester
- indirect protection by vaccinating all household contacts at least 2 weeks before beginning contact if over 10 years since last dose

15

Transmission of varicella zoster

Aerolised droplets from nasopharyngeal secretions
OR
Direct cutaneous contact with vesicle fluid from skin lesions

16

Virology of varicella zoster

dsDNA virus
Enveloped with glycoprotein spikes

17

Average incubation period of chicken pox

14-16 days

18

Clinical features of chicken pox

GENERALISED VESICULAR RASH + FEVER
Prodrome: low-grade fever, malaise, pharyngitis, anorexia
Rash develops within 24 hours
Begins on trunk/face then spreads to extremities
Rash typically has lesions in different stages (macule-papule-vesicle-pustule-crusted papule)
New vesicle formation ends by day 4
Most lesions fully crusted by day 6

19

Complications of chicken pox

Most common in infants, elderly or immunocompromised
- Skin/soft tissue infections
- Neurological (Encephalitis, Reye syndrome, transient focal deficits, aseptic meningitis, transverse myelitis, vasculitis, hemiplegia)
- Pneumonia
- Hepatitis
Diarrhoea, pharyngitis, otitis media

20

Management of chicken pox

Self-limiting in uncomplicated disease of immunocompetent patients
Isolation until all lesions fully crusted over (generally 6 days)
Symptomatic (calamine lotion, cool compresses, antihistamines at night)
Cut nail shorts to avoid secondary infection
Oral aciclovir if significant pre-existing skin disease
IV or oral acyclovir if complicated or immunocompromised patient

21

Epidemiology of measles
(peak age, complication rate, contagiousness)

Peak age at 6m (vaccination occurs at 12m, maternal antibodies become ineffective at 6m)
Overall complication rate 22% (mainly diarrhoea, AOM, pneumonia)
90% infection rate for susceptible household contacts

22

Risk factors for measles

Children too young for vaccination
Unvaccinated children or those who have not completed their second dose of the vaccine
Travel or contact with ill people from the developing world

23

When is measles contagious

Contagious from 5 days before the onset of the rash to 4 days after
Most contagious during late prodrome phase (fever + respiratory symptoms)

24

Clinical features of measles

Prodrome (2-3 days)
- fever, malaise, anorexia, conjunctivitis, coryza, cough
- may develop Koplik's spots
Exanthem stage:
- maculopapular blanching RED rash begins on face, spreads caudally
- PALMS AND SOLES NOT INVOLVED
- lymphadenopathy
- high fever, peaking 2-3 days after rash appears
- pronounced respiratory symptoms
- cough persists for 1-2 weeks, fever for 3-4 days after rash onset

25

Incubation period of measles

6-19 days (median 13)
ie 2 weeks

26

What are Koplik spots

Pathognomic for measles
1-3mm white/grayish/bluish elevations with erythematous base on buccal mucosa opposite molar teeth, often begin to slough when rash appears

27

Definition of diphtheria

An acute infectious respiratory disease caused by toxigenic strains of Corynebacterium diphtheriae named after the Greek word for leather, referring to the tough pharyngeal membrane that is hallmark of the infection

28

Microbiology of Corynebacterium diphtheria

Gram-positive bacillus
Non-sporing
Non-capsulate

Produces exotoxin that acts locally on mucous membranes of respiratory tract and systemically on myocardium, nervous system and adrenal glands

29

Clinical features of diphtheria

Gradual onset of symptoms
Sore throat, malaise, cervical lymphadenopaty, low-grade fever
Mild erythema, progressing to spots of gray and white exudate
Myocarditis (SOB, red HS, gallop rhythm)
Renal failure
Neurological toxicity (5%)
- local neuropathies (soft palate, posterior pharynx)
- cranial neuropathies (oculomotor, ciliary, facial, laryngeal)

30

Management of diptheria

Erythromycin
Diphtheria antitoxin if severe
Careful airway management
Serial ECGs
Monitor neuro status
Droplet precautions
Isolation until 2 consecutive cultures taken at least 24 hours apart are negative