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Fatal Case of Diphtheria

문서에서 ENB Quarterly (페이지 25-33)

On 3 August 2017, the Ministry of Health (MOH) was notified of a case of diphtheria involving a 23-year-old Bangladeshi male, who had been working for a construction firm in Singapore. He stayed in a multi-storey dormitory, and had no recent travel history nor any known sick contact. The case developed fever and neck pain on 30 July 2017, and sought treatment at Yishun Polyclinic. However, initial symptomatic treatment and antibiotics did not afford any relief, and he subsequently presented to Khoo Teck Puat Hospital (KTPH) Emergency Department on 1 August 2017 with painful swallowing, difficulty breathing and cough with bloody sputum. During an emergency tracheostomy, severe swelling and the classic pseudomembrane was observed in his airways.

While admitted, the case received intravenous antibiotics and diphtheria anti-toxin. However, despite the prompt treatment, the patient deteriorated rapidly and passed away on 4 August 2017.

Figure 1. Multi-storey workers dormitory in the vicinity where the case lived Reported by Guanhao Chan, Yingqi Lai, Pei Pei Chan

Communicable Diseases Divison, Ministry of Health, Singapore NOTES FROM THE FIELD

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Figure 2. Dormitory room where the case lived with 11 other workers What is diphtheria?

Diphtheria is an acute respiratory or cutaneous infection caused by the gram-positive bacilli Corynebacterium diphtheriae. It is typically transmitted from person-to-person via respiratory droplets or direct contact with respiratory secretions. The bacteria’s pathogenicity stems from the production of diphtheria toxin, which is responsible for the classic manifestations of respiratory diphtheria.

A potentially fatal infectious disease, the average case fatality rate for individuals infected with diphtheria is between 5-10%, and is higher in younger children and older adults. Death usually result from complications such as myocarditis and neuritis, which occur as a result of systemic circulation of the diphtheria toxin.

Despite its virulence, diphtheria is a disease that can be prevented by immunization with diphtheria toxoid-containing vaccine. Since the development of the diphtheria vaccine in 1923, the incidence of diphtheria has gradually declined in most countries, with fewer than 10,000 cases reported globally in 2016.

Why was this case of diphtheria significant?

Singapore had remained free of diphtheria in the past 25 years, with the last local and imported cases occurring in 1992 and 1996 respectively. This could be attributed to the high diphtheria immunization coverage in the local population, as vaccination against diphtheria was made mandatory for Singaporean

children in 1962. Since then, the National Childhood Immunisation Schedule has stipulated that all children should receive a primary course of diphtheria toxoid -containing vaccine (e.g. TDaP or DTP) at four and five months of age, and boosters given at 18 months and 10-11 years of age. Immunization coverage among children aged two has been maintained at 96-98% in the past decade.

Nevertheless, as a global city, there remains the risk of importation and transmission of diphtheria via pockets of unvaccinated individuals in the community. These vulnerable populations include foreign or migrant workers, who are primarily sourced from Bangladesh, India, Myanmar, China and Malaysia, countries which are endemic for diphtheria. In this instance, the case was living in a dormitory with an estimated 8000 other foreign workers, majority of whom had no verifiable history of immunisation against diphtheria. With a fairly high R0 of 6-7, compounded by the cramped living conditions in the dormitory, the infection could have spread quickly and led to a large outbreak of diphtheria within the dormitory.

Furthermore, the infection was undoubtedly acquired locally as the case had not left Singapore in the past ten months. Asymptomatic carriage of diphtheria in the nose and throat is known to occur even in vaccinated individuals, but the level of carriage in the local population is uncertain. To this date, the reservoir of infection remains unknown.


What were the public health measures instituted by MOH?

Upon receiving the notification, MOH acted quickly to confirm the diagnosis of diphtheria. Samples taken from the case’s airway grew C. diphtheriae on non-selective media and selective Tinsdale agar. The National Public Health Laboratory (NPHL) subsequently confirmed the presence of toxin genes in the C. diphtheriae isolates on 4 Aug 2017.

Concurrently with laboratory confirmation, MOH began gathering epidemiological information about the case from the case’s employer and dormitory manager. The employer was instructed to send the case’s close contacts i.e. the dormitory roommates and worksite colleagues, to the Communicable Disease Centre (CDC) on 4 Aug 2017 for screening and post-exposure prophylaxis.

Interviews with the employer, dormitory manager and close contacts were conducted to determine the case’s movement history before his admission to hospital.

Fortunately, his movements were mainly confined to his dormitory room and worksite, which minimised his exposure to the other dormitory residents and the community at large.

All close contacts that were exposed to the case, including healthcare workers providing direct care without personal protective equipment at Yishun Polyclinic and KTPH, were prescribed a course of antibiotics and given a booster vaccine. Screening throat swabs of the dormitory and worksite contacts were obtained and sent for concurrent culture on selective media at National University Hospital Laboratory and for PCR at NPHL. Thankfully, none of the contacts were tested positive for C. diphtheriae or eventually developed symptoms of diphtheria.

What were the challenges faced by MOH managing this case of diphtheria?

With an estimated 8,000 foreign workers who were living in the same dormitory as the case, MOH made

an assessment to clearly define, trace and provide post-exposure prophylaxis (PEP) only for the contacts that were exposed and at greatest risk of developing infection. MOH solicited the aid of the dormitory managers as well as the case’s employer to identify these close contacts for follow-up actions. In addition, the dormitory managers and employer were informed to actively monitor the health of their workers, and to inform MOH if any of them developed respiratory symptoms. Unfortunately, monitoring efforts were beset by indifference on the part of the dormitory supervisors and employers, who neglected to inform Figure 3. Timeline of events and public health actions

Figure 4. One of the worksites of the housing estate in which the case had worked


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Figure 5. Workers at CDC awaiting medical assessment and post-exposure prophylaxis NOTES FROM THE FIELD

MOH when sending sick workers to hospital. This might have led to an exposure of hospital staff and patients, as the hospital Emergency Department could not be informed ahead of time to take the necessary precautions and control measures.

MOH officers encountered significant language difficulty in interviewing the case’s close contacts, who were mainly of Bangladeshi and Burmese nationality.

The language barrier between MOH officers and the contacts impeded the gathering of epidemiological information as well as educating the contacts of public health measures being taken. Luckily, MOH was able to request the help of the worker’s supervisor, who was bilingual in English and Bengali, and also a fellow MOH officer who could speak Burmese.

As with any large operation, MOH experienced some hiccups in the coordination between multiple stakeholders e.g. case’s employer, CDC, KTPH, Yishun Polyclinic, and the Ministry of Manpower. In one instance, the CDC experienced a larger-than-expected number of workers for screening and PEP, due to an unexpected number of workers from the same company who showed up, but who had no contact with the case. Communications with the employer could have been improved to ensure that only contacts were screened and received PEP.

In the modern era of big data analytics, it is easy to discount the astute physician on the ground, who in this case had recognized early the textbook clinical manifestations of diphtheria despite not having encountered the disease before. The prompt diagnosis and notification to MOH enabled public health actions to be taken promptly, reducing the window for spread of the disease to occur. The role of continuing medical education for clinicians cannot be more emphasized in this case.

Despite the high vaccination coverage of the general Singaporean population due to mandatory vaccination, there remain considerable subpopulations that have less than ideal vaccination coverage. This case of a severe, vaccine-preventable disease in a foreign worker, has underscored such a gap in vaccine coverage.

Similar to most other developed countries, Singapore currently has no requirements for vaccination of immigrant workers. MOH will need to engage other relevant agencies to improve vaccination uptake and implement recommendations from the National Adult Immunisation Schedule, for all foreigners seeking work in Singapore.

Image courtesy of A/Prof Hsu Li Yang, TTSH


Figure 6. A worker receiving his booster dose vaccine with a seven day course of oral antibiotics

Image courtesy of A/Prof Hsu Li Yang, TTSH

30 | ENB Quarterly | Vol 44 (1) FAST FACTS




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As of E-Week 52 (24 - 30 Dec 2017)

Infectious Diseases Update


* Preliminary figures, subject to revision when more information is available.

E Week 52 52 Weeks



E Week 52 52 Weeks



E Week 52 52 Weeks









Distribution (%) of influenza type


Monthly Influenza Surveillance

A(H3N2) A(H1N1)pdm09 Indeterminate (low viral titre) B


0 500 1000 1500 2000 2500 3000 3500 4000

1 3 5 7 9 11 13 15 17 19 21 23 25 27 29 31 33 35 37 39 41 43 45 47 49 51 Average daily no.


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