Diphtheria Flashcards
What organism causes diphtheria?
Corynebacterium diphtheriae or C. ulcerans
Diphtheria can be caused by toxigenic strains that produce exotoxin.
How is diphtheria transmitted?
Respiratory droplets person-to-person, rarely via fomites
Usually requires close, prolonged contact.
C. ulcerans zoonotic - animal contact, raw milk
What are the clinical features of diphtheria?
Asymptomatic carriage, pharyngitis/laryngitis, thick adherent membrane on pharynx, cervical lymphadenopathy, surrounding edema.
Cutaneous: lesions on exposed parts, vesicles, small well-demarcated ulcers. Can be toxigenic strain or non.
Complications include renal failure, neuropathy, and cardiomyopathy.
What is the case fatality rate (CFR) of diphtheria?
Previously 5-10%
This statistic may vary depending on treatment access and public health measures.
Who are considered high-risk groups for diphtheria?
Children < 5 years old and adults > 40 years old
These groups are more likely to experience severe disease.
What are the case definitions for diphtheria?
Confirmed: isolation of toxigenic strain + clinical.
Probable: isolation toxin production unknown + clinical
OR clinical + epi
Clinical + epidemiological link can also define probable cases.
What is the incubation period for diphtheria?
Usually 2-5 days
How long is the infectious period for diphtheria?
2-4 weeks
Non-infectious after 48 hours of antibiotics. Chronic carriers can shed organisms for > 6months.
What is the vaccination schedule for diphtheria in children?
DTPa at 2, 4, 6, and 18 months, and at 4 years old
Booster dTpa at 12-13 years (year 7). Pregnant women - 1 x dTPA vaccine each pregnancy.
Vaccination (dTpa) also recommended for adults age 50y and 65y if last dose ≥10y ago, and any adolescents/adults who have not been vaccinated (should have 3 dose course plus 2x boosters at 10y intervals).
What treatment is recommended for diphtheria?
Antitoxin (DAT) and 14/7 antibiotics (penicillin or azithromycin)
Clearance testing is required 24 hours after antibiotics.
What are the exclusion criteria for asymptomatic contacts of diphtheria?
Children no school/childcare until 2x negative tests; adults no work until test negative
Especially important for food handling, healthcare, and early childhood care.
What should be done for contacts of diphtheria cases?
Ask about recent travel; nose/throat swabs, wound swabs if applicable
Clearance antibiotics and vaccination are recommended.
What is the definition of a contact of a diphtheria case?
Co-travellers, household, kissing/sexual, HCW if mouth-to-mouth resus / wound dressing, share sleeping area / kitchen, childcare centre (multiple hours)
Consider visitors, school, workplace, other HCWs.
Time period: since wound onset OR previous 7 days.
True or False: Diphtheria is common in Australia.
False
Diphtheria is very rare in Australia; most cases are cutaneous and overseas-acquired. Non-toxigenic strains likely endemic (asymptomatic carriers).
What is the primary method for diagnosing diphtheria?
Pharyngeal/wound swab for culture and toxigenicity testing; PCR for toxigenic status
Reference lab for further confirmation may be required.
What percentage of diphtheria cases in Australia were fully vaccinated?
38%
Indicates a significant portion of cases occurred in unvaccinated individuals.
Fill in the blank: The organism responsible for diphtheria is __________.
Corynebacterium diphtheriae
