Paediatric Infectious Disease Flashcards
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
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)
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)
Congenital rubella syndrome
Most likely if maternal rubella infection in first trimester of pregnancy Hearing loss Mental retardation Cardiovascular defects Ocular defects
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
Rubella vaccination
Live attenuated
Recommended at 12 & 18 months
Contraindications: pregnancy, immunocompromised
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
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
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
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)
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
Complications of pertussis
Apnoea
Pneumonia (most common cause of death)
Weight loss secondary to feeding difficulties and post-tussive vomiting
Seizures and encephalopathy
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
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
Transmission of varicella zoster
Aerolised droplets from nasopharyngeal secretions
OR
Direct cutaneous contact with vesicle fluid from skin lesions
Virology of varicella zoster
dsDNA virus
Enveloped with glycoprotein spikes
Average incubation period of chicken pox
14-16 days
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
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
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
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
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
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)
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
Incubation period of measles
6-19 days (median 13)
ie 2 weeks
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
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
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
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)
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
Virology of mumps
Paramyxovirus from Rubulavirus genus
SS RNA genome
Rapidly inactivated by formalin, ether, chloroform and light
transmission via aerosol and direct contact with saliva
Clinical features of mumps
Asymptomatic in 30% Non-specific symptoms: - fever - headache - malaise - myalgia - anorexia Specific symptoms - bilateral parotid swelling (60-70% clinical cases) - meningeal symptoms in 10% - Orchitis (usually unilateral) in 15% of postpubertal males May result in spontaenous abortion in first trimester of pregnancy
Mumps in pregnancy
May result in spontatneous abortion
Maternal infection not associated with increased risk of congenital malformation
Management of mumps
No specific treatment
Supportive management: paracetamol for pain/fever
Avoid sour foods - increase salivation, increase parotid pain
Liquid diet may help if pain on swallowing
Definition of tetanus
A nervous system disorder caused by the tetanus toxoid from Clostridium tetani and characterised by muscle spasms
Microbiology of tetanus
Clostridium tetani:
- obligate anaerobe in soil
- spores gain access to damaged human tissue
- rod-shaped bacterium
- produce tetanus toxin (metalloprotease tetanospasmin)
Toxin reaches spinal cord and brainstem via retrograde axonal transport, irreversibly blocking receptors hence neurotransmission
Predisposing factors for tetanus
Will not grow in healthy tissues, therefore usually requires 2+ of the following:
- penetrating injury resulting in inocculation of C. tetani spores
- Coinfection with other bacteria
- Devitalised tissue
- Foreign body
- Localised ischaemia
Name of tetanus toxin
Metalloprotease tetanospasmin
Clinical features of tetanus
Incubation period 7-10 days (shorter in neonates)
Generalised tetanus:
- trismus (lockjaw)
- Autonomic overactivity in early phases (irritability, sweating, tachycardia)
- stiff neck
- Opisthotonus (arched back)
- Sardonic smile
- Board-like rigid abdomen
- periods of apnoea or upper airway obstruction
- Dysphagia
Management of tetanus
Long lasting effects, 4-6 weeks of clinical symptoms
ICU management
- Penicillin and metronidazole (stop toxin production)
- Neutralisation of unbound toxin (human tetanus Ig)
- Active immunisation - does not confer immunity following recovery from acute illness (3 doses of DTP at least 2 weeks apart)
- Control muscle spasms (benzos, propofol, rocuronium etc.)
- Manage autonomic dysfunction (MgSulfate, beta blockers e.g. labetalol, atropine, clonidine, epidural bupivacaine)
- Airway management (early intubation, tracheostomy likely needed)
- Nutritional support
- VTE prophylaxis
- Physical therapy as soon as spasms ceased
Tetanus prophylaxis
Tetanus vaccine to anyone who has completed only the primary series of immunisation or who received a booster over 5 years ago and has sustained a puncture wound
Tetanus toxoid AND tentaus immune globulin should be given to patients with puncture wounds who have received less than 3 doses of immunisation in the past or whose immunisation status is uncertain
