Infectious Disease

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Infectious Disease

• Hugh Mc Gann
• Department of Infectious Diseases Seacroft
  Hospital

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Assessment of patients with infections

• History
• Examination
• Investigations

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History

• Specific symptoms e.g. fever, rigors, sweats
• Risk factors for infection
• Travel
• Infectious contacts
• Occupation
• Pets/birds
• Sex/needles
• Time since exposure/how long unwell
• Previous medical problems/medications

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Investigations 1

• Baseline blood tests
• Inflammatory markers PV, ESR,CRP
• LFTS
• Culture things
• Pus
• Blood
• Urine
• Sputum
• CSF
• Biopsies

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Investigations 2

• Serology Measure antibodies to specific
  infections IgG/IgM
• Molecular methods
• DNA amplification-PCR
• Radiology
• Plain X-rays
• Ultrasound
• CT/MRI
• Isotope scans

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Immunity and Vaccination
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Immunity 1

• Innate Immunity
• General or non specific host defences which
  provide the initial protection against microbes
• Physical skin, mucous membranes, intestinal
  tract, eye
• Colonisation resistance by the normal flora
• Mechanical removal sneezing, coughing
• Non-specific immune system phagocytosis,
  complement, cytokines, natural killer cells

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Immunity2

• Specific immunity
• Characterised by antigen specificity, memory and
  heightened response on subsequent antigen
  exposure
• Humoral immunity B cell receptors-Antibodies-act
  ivation of complement by classical pathway
• Cell mediated immunity T cell receptors-cytotoxic
  T cells

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Vaccination

• The act of artificially inducing immunity or
  providing protection from disease
• Vaccines have led to the global eradication of
  smallpox, elimination of polio from western world
  and reduced incidence of many common disease

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Vaccination 2

• Active Immunisation
• A vaccine which stimulates bodys immune system
  to produce antibodies or cell mediated immunity
• Live (attenuated infectious agents) Immunological
  response similar to that of natural infection.
  Life long immunity with one dose
• Promote cell mediated immunity
• MMR, polio(o), yellow fever

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Vaccination 3

• Active Immunisation
• Inactivated (contain components of the organism
  or exotoxin) Diptheria, whooping cough, tetanus,
  HiB
• Need repeated vaccinations and boosters to obtain
  high level/long lasting immunity
• 1st(/2nd) injection produces slow antibody
  response-IgM
• Subsequent injections give accelerated and higher
  level of antibodies IgG

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Vaccination 4

• Passive immunisation short term protection by
  injecting human immunoglobulin. Immediate
  protection but only for a few weeks
• Human normal immunoglobulin
• Hepatitis A, measles
• Specific immunoglobulin
• Varicella zoster, hepatitis B

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Vaccination 5

• Childhood vaccine schedule
• 3 doses at 234 months HiB, DTP, Polio,
  Meningococcus group C
• 12-15 months MMR
• 3-5 years DT, Polio, MMR
• 10-15 years DT, P, Polio
• BCG

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Herpes viruses

• Herpes Simplex Virus 1and 2
• Varicella Zoster
• Cytomegalovirus
• Epstein Barr (Infectious Mononucleosis)
• Human Herpes Virus Type 6 and 7
• Human Herpes Virus Type 8(Kaposi sarcoma
  associated herpes virus)

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Herpes Simplex

• HSV 1 and 2 cause clinically indistinguishable
  infection.
• Primary infection systemic illness
• Gingivostomatitis and pharyngitis
• Genital infection
• Reactivation
• Genital HSV 2 more likely to reactivate
• Oral-labial HSV 1 more likely to reactivate

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Varicella Zoster Virus 1

• Causes 2 distinct clinical diseases
• Chicken Pox(varicella zoster) This is the primary
  infection.
• Very contagious
• Incubation period 10-14 days
• Benign illness in children
• Fever, vesicular rash, this then pustulates and
  scabs

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Varicella Zoster virus 2

• Shingles (Herper Zoster) reactivation of VZV
  which is latent in the dorsal root ganglia
• Occurs in those who have had chickenpox, usually
  elderly
• Vesicular rash with dermatomal distribution
• H.Z. ophthalmicus, maxillary/mandibular V
• Ramsay Hunt syndrome

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Infectious Mononucleosis 1

• Epstein Barr virus
• Acute illness with sore throat (bilateral
  exudative tonsillitis), fever and lymphadenopathy
• Ampicillin causes a rash in 90-100
• Palatal petechiae in up to 60
• Abnormal LFTs in 90

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Infectious Mononucleosis 2

• Usually resolves within 2-3 weeks
• Diagnosis by GFST (Paul-Bunell or monospot which
  detect heterophile antibodies
• Atypical lymphocytes on blood film

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Childhood Rashes

• Measles
• Rubella
• Scarlet Fever
• Erythema Infectiosum
• Exanthem Subitum

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Measles

• Marked decrease in incidence since vaccine
• Highly infectious, spread by droplets from
  respiratory secretions
• Incubation period of 10 - 14 days
• Diagnosis, clinical, confirmed by specific IgM in
  blood/saliva
• Complications pneumonia, encephalitis

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Measles Clinical features

• Prodrome, malaise, fever, conjunctivitis and
  coryzal symptoms
• Kopliks spots bluish grey grains on a red base
  on buccal mucosa opposite 2nd molars
• Rash purplish maculopapular, initially on the
  face, extends down the body
• Illness lasts 7-10 days

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Scarlet Fever

• Streptococcal infection- Group A Strep.
• Streptococcal strain wgich produces an
  erythrogenic toxin
• Pharyngitis
• Rash on 2nd day of illness
• Flushed face(circumoral pallor)
• Strawberry tongue

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Rubella

• Mild illness, often subclinical
• Rubella virus first isolated in 1962, recognised
  clinically from 19th century
• Spread droplets from respiratory secretions
• Usually primary school children.
• Infection in pregnancy can cause foetal infection
  (congenital defects, foetal death)

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Rubella, Clinical Features

• Incubation period 10-18 days
• Rash pink macular, face and trunk on day 1,
  limbs day 2, disappears day 3/4
• Lymphadenopathy posterior cervical and sub
  occipital nodes
• Conjunctival and pharyngeal injection
• Diagnosis by specific rubella IgM

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Erythema Infectiosum

• Often called slapped cheek or fifth disease
• Caused by Parvovirus B19
• Facial rash sometimes preceded by mild fever
• Rash slapped cheek appearance, resolves in about
  1 week but can recur with exposure to heat

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Exanthem subitum

• Called roseola infantum or sixth disease
• Caused by HHV-6
• Benign illness of infants/children
• Rash preceded by 3-4 days of high fever, upper
  respiratory symptoms
• Rash maculopapular on trunk/limbs

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Mumps

• Viral illness mostly in children/adolescents
• Spread by droplets, incubation 2-4 weeks
• Prodrome of fever, malaise, headache
• Parotid gland enlargement (lifts ear up and out)
  usually bilateral, unilateral in 25
• May involve other salivary glands
• Complications orchitis and meningitis

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Whooping Cough 1

• Bordetella Pertussis
• Higher incidence and increased severity in girls
• Disease of childhood but now mostly seen in
  adults because of vaccination
• Disease most severe in infants
• Incubation period 1-3 weeks

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Whooping Cough 2

• Catarrhal phase malaise, low grade fever, runny
  nose and eyes
• Paroxysmal phase typical cough-Whoop
• Blood tests show high white cell count
• Complications secondary infection, physical
  sequelae of paroxysms of coughing