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Everything is common, and everything is fatal!


  • Viral exanthema
  • Other common viral infections
  • Common bacterial infections
  • Common fungal infections
  • Worm and parasite infestations

Why do children get infections?

Get infections on average 7-8 times per year

  • Heavy mixing: no sense of personal space
  • Poor hygiene: dirty habits
  • Low or absent adaptive immunity (do have innate immunity)

Viral exanthema


Slapped cheek syndrome

  • aka erythema infectiosum, Fifth disease
  • Caused by parvovirus B19
  • Fevers followed several days later by erythema of the cheeks and ‘reticular’ (lace-like) rash of the limbs
  • Also small joint arthritis in adolescents, adults
  • Associated with hydrops fetalis and intrauterine death and also severe anaemia in children with haematologic disorders (affects red cell precursors for a few days - completely wiping them out for a few days. In a normal person that's not a big deal, but people with an underlying problem can have realy problems)


  • aka chicken pox
  • Fever and rash with macules‐papules‐vesicles‐pustules (lesions in each of these stages of infection are present at any one time; characteristic of this infection)
  • Itchy
  • Also in mouth
  • Secondary infection with Strep pyogenes/ Staph aureus
  • Spread by respiratory route and direct contact
  • Vaccine preventable but vaccine is <100% effective
    • Still see cases: not all children are vaccinated and the vaccine isn't 100% effective

Hand, foot and mouth disease

  • Caused by enterovirus infection, of which many types
  • Coxsackie A19 most commonly implicated enterovirus
  • Vesicular lesions on hands and feet and mouth ulcers
  • Low grade fevers
  • Common in pre‐school and early school ages
  • Spread by faecal‐oral route


  • Caused by human herpes virus (HHV) 6 or 7
  • Infection is practically universal between ~6m and 2yr (peak 9‐12m) as maternal antibodies wane.
  • High fever for 2‐3d followed by diffuse rash as fever settles (distinctive rash, diagnostic)
  • Common cause of febrile convulsions


  • Once common, now uncommon because of vaccination
  • High fevers and diffuse rash preceded by coryzal symptoms (runny nose, infection of conjunctiva)
  • Miserable ++
  • Contageous ++
  • Transmission is purely airborn
  • Risk in unvaccinated/undervaccinated and travellers
  • Risk of acute encephalopathy, deafness, death and late complication SSPE (Subacute sclerosing panencephalitis; uniformly fatal)
  • Similar appearance to drug-related rash except they have conjunctivitis and are miserable


  • aka German measles
  • Less severe than measles
  • Also uncommon because of vaccination
  • Starts on the head and then trunk and limbs
  • Occipital lymph nodes
  • Benign infection, but
    • Congenital infection is the most important complication
      • Includes congenital cataracts

Respiratory syncitial virus (RSV)

  • Most common cause of bronchiolitis in infants (~75%)
  • Most severe in infants <6m or those with underling heart, lung or neurological disease
  • ?predisposes to subsequent development of asthma
  • Also important in immunocompromised patients
  • Partially preventable by passive immunisation with monoclonal antibodies -- give to vulnerable children e.g. premature babies (no effective active immunisation)

Infectious mononucleosis

  • Usually caused by Epstein‐Barr virus (part of herpesvirus group including genital herpes and varicella)
  • Sometimes caused by cytomegalovirus
  • Infection in young children usually asymptomatic
  • Infection in adolescence frequently results in fever, exudative tonsillopharyngitis (pus forms on tonsils), lymphadenitis
  • Sometimes hepatitis

Herpes simplex

  • Causes cold sores and genital lesions in adolescents and adults.
  • Primary infection can cause severe gingivo‐stomatitis in young children.
  • Also can cause skin lesions (whitlow), usually on hands, fingers or limbs.
    • Clusters of vesicles = herpes simplex
  • Also can cause encephalitis (fatal) and sepsis‐like syndrome, esp in young infants.

Herpes is for life, remains dormant and recurs (recurrent coldsores and genital lesions)

Molluscum contagiosum

  • Infection with a pox virus
  • Umbilicated papules, 2‐5mm lasting 6m – 2yr
    • Not fluid, but solid and rubbery, with a little core you can squeeze out. Last for a long time (weeks/months/years)
    • Core is where virus lives; squeeze this out and it will resolve
    • Cauterizing can also work (not good if you have many of them)
  • Face, trunk and limbs
  • Lesions may be mechanically removed, frozen, cauterised
  • Transmission via direct contact +/‐ fomites, autoinnoculation

Common warts

  • aka verruca vulgaris
  • Infection with human papilloma virus (same virus responsible for cervical cancer; different strain)
  • Circumscribed, raised or flat, hyperkeratotic lesions 1mm‐ 1cm
  • Usually fingers, limbs, sole of foot
  • Rarely the upper +/‐ lower respiratory tract
    • Especially in infants born to women who have the virus in genital tract
    • Infects vocal cord
  • Transmission via direct contact
  • Flatter on the sole of the foot, difficult to treat

Parainfluenza virus

  • Most common cause of croup in infants and young children
  • Also causes bronchiolitis and ‘common cold’ in children/adults
  • Transmission is by contact with droplets
  • Croup is an infection of the upper part of the airway (trachea, vocal cord, hoarseness, croupy cough)


  • Most common cause of severe gastroenteritis in children
  • All children infected by 5 years, most by age 2 years
  • Easily transmitted by faecal‐ oral route
  • Both vomiting AND diarrhoea
  • Common cause of dehydration and death in developing countries
  • Now preventable by vaccination with a live attenuated vaccine. Expensive vaccine, not used everywhere



  • aka school sores
  • Very common in pre‐school and school‐aged
  • Contageous by direct contact
  • Usually Streptococcus pyogenes (group A strep), sometimes Staph aureus
  • Thin‐walled vesicles/ bullae, honey‐coloured ooze, crusting
    • Vesicles beak open and normally you see them having broken open already
  • Treat with topical disinfectants, oral antibiotics
  • Don't normally get sick from this


  • Usually after inoculation, eg insect bite, wound
  • Usually affecting limb, in children periorbital & perianal cellulitis also occur
  • Strep pyogenes and Staph aureus most common, Strep pneumoniae if periorbital
  • If associated with animal bites or water exposure may be due to other organisms
  • Tracking appears, from following the lymph drainage (typical of group A streptococcus)
  • Periorbital cellulitis is okay, but orbital cellulitis is a big deal (treat aggressively)

Scarlet fever

  • Sequela of Strep pyogenes infection
  • Secondary to scarlatina toxin production, that produces additional manifestations
  • Usually associated with pharyngitis
  • Unusual before 5 yo
  • Distinctive diffuse sand‐paper rash (easier to feel than to see)
  • Strawberry tongue (red beefy tongue with white papillae)
  • Peripheral skin peeling
  • Infection can be severe, more commonly fairly benign
  • For some reason, the types of scarlet fever seen these days are less serious than in years gone by


There's a question about this in the exam.

  • aka whooping cough
  • Caused by Bordetella pertussis
  • Characteristic paroxysmal coughing illness (coughing fits) with post‐tussive whoop
  • Was made uncommon by vaccination
  • Over past 5‐10 years, increasing cases, esp amongst older children and adolescents
  • Vaccine only partially protective (can have mild infection in parents, and it can spread to the infant)
  • Unvaccinated infants < 4m at highest risk
  • Transmission by droplets, esp from infected adults, carers etc
  • Should vaccinate the parents and the immediate household members to prevent infection of those who are too young to be vaccinated.


  • Range of manifestations due to infection with Strep pneumoniae
    • Otitis media/ sinusitis
    • Pneumonia
    • Bacteraemia/ sepsis
    • Meningitis
    • Septic arthritis
    • Common coloniser of the nasopharynx
  • Young infants at highest risk of invasive infection
  • Growing resistance to penicillin
  • Many but not all serotypes preventable by vaccination

Most important cause of bacterial pneumonia in both children and adults.

Urinary tract infections

  • One of the most common bacterial infections of children
  • Usual organisms are enteric, E coli, Klebsiella
  • Uncircumcised boy infants at highest risk. In other age groups females at higher risk.
  • Vesico‐ureteric reflux is a risk factor.
  • May result in bacteraemia, sepsis, meningitis in infants