Diphtheria

Question 1

What organism causes diphtheria?

Answer 1

Corynebacterium diphtheriae or C. ulcerans

Diphtheria can be caused by toxigenic strains that produce exotoxin.

Question 2

How is diphtheria transmitted?

Answer 2

Respiratory droplets person-to-person (usually requires close, prolonged contact), rarely via fomites.

C. ulcerans zoonotic - animal contact, raw milk

Question 3

What are the clinical features of diphtheria?

Answer 3

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.

Question 4

What is the case fatality rate (CFR) of diphtheria?

Answer 4

Previously 5-10%

This statistic may vary depending on treatment access and public health measures.

Question 5

Who are considered high-risk groups for diphtheria?

Answer 5

Children < 5 years old and adults > 40 years old

These groups are more likely to experience severe disease.

Question 6

What are the case definitions for diphtheria?

Answer 6

Confirmed: isolation of toxigenic strain + clinical.

Probable: isolation toxin production unknown + clinical
OR clinical + epi

Clinical + epidemiological link can also define probable cases.

Question 7

What is the incubation period for diphtheria?

Answer 7

Usually 2-5 days

Question 8

How long is the infectious period for diphtheria?

Answer 8

2-4 weeks

Non-infectious after 48 hours of antibiotics. Chronic carriers can shed organisms for > 6months.

Question 9

What is the vaccination schedule for diphtheria in children?

Answer 9

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).

Question 10

What should be asked in the case interview for diphtheria?

Answer 10

Symptoms, vaccination, travel history, animals/raw milk, contacts, IPC

Question 11

What treatment is recommended for diphtheria?

Answer 11

Antitoxin (DAT) and 14/7 antibiotics (penicillin or azithromycin)

Clearance testing is required 24 hours after antibiotics.

Question 12

How should diphtheria contacts be managed?

Answer 12

• Clearance ABx
• PEPV - 1 x DTPa (vaccinated); full course (unvaccinated)
• Education re: transmission
• Active follow-up 7/7

Question 13

What are the exclusion criteria for asymptomatic contacts of diphtheria?

Answer 13

Children no school/childcare until 2x negative tests; adults no work until test negative

Especially important for food handling, healthcare, and early childhood care.

Question 14

What should be done for contacts of diphtheria cases?

Answer 14

Ask about recent travel; nose/throat swabs, wound swabs if applicable

Clearance antibiotics and vaccination are recommended.

Question 15

How long should cases isolate for?

Answer 15

Until clearance testing complete.

Question 16

What is the definition of a contact of a diphtheria case?

Answer 16

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.

Question 17

True or False: Diphtheria is common in Australia.

Answer 17

False

Diphtheria is very rare in Australia; most cases are cutaneous and overseas-acquired. Non-toxigenic strains likely endemic (asymptomatic carriers).

Question 18

What is the primary method for diagnosing diphtheria?

Answer 18

Pharyngeal/wound swab for culture and toxigenicity testing; PCR for toxigenic status

Reference lab for further confirmation may be required.

Question 19

What percentage of diphtheria cases in Australia were fully vaccinated?

Answer 19

38%

Indicates a significant portion of cases occurred in unvaccinated individuals.

Question 20

Fill in the blank: The organism responsible for diphtheria is __________.

Answer 20

Corynebacterium diphtheriae