ARCHIVED - Outbreak of tuberculosis in the Laurentian region, 2005

1 October 2006

Volume 32

Number 19

D Décarie, MD (1), J-L Grenier, MD (1), A Allard, MD (1)

1. Équipe des maladies infectieuses, Direction de santé publique des Laurentides,
   Saint-Jérôme, Québec

Introduction

On 3 June 2005, the Direction de santé publique des Laurentides received a phone call from a pediatrician at a children's hospital. The pediatrician stated that a 2-month-old infant had been hospitalized with meningitis. He suspected tuberculous meningitis because the father, originally from Haiti, had been coughing for nearly 1 year and was presenting with cavities on his chest X-rays. The father's sputum was strongly positive for auramine, and the diagnosis was confirmed by PCR and culture. However, the diagnosis could not be confirmed in the child in either the cerebrospinal fluid or the gastric aspirate. Both individuals responded well to standard treatment.

Investigation

An investigation of the source case's immediate family was initiated. This group consisted of individuals who were currently living or had recently lived in the same household (circle 0): the current spouse, ex-spouse and mother of the sick infant, and her daughter from a previous relationship. All had significant TST results. Screening was then performed on the extended family, half-brothers, families of the source case and the two spouses, and then close friends (circle 1). Most of these people were young and born in Quebec, and the significant TST rate in these contacts was substantially above the expected prevalence. One individual, a young girl, was diagnosed with probable tuberculosis based on a cough that had recently appeared, an X-ray compatible with active tuberculosis and adequate response to anti-tuberculosis therapy. A halfbrother was also diagnosed with pulmonary tuberculosis as a result of the investigation that followed screening. It therefore became appropriate to extend the investigation to the workplace, a food service establishment with approximately 150 employees. Study of this environment, based on inspection, an employee questionnaire and analysis of the ventilation system, identified three levels of exposure. The standard method of investigation by concentric circles was used. Investigation began with individuals working in the same room as the source case, the bar (circle 2). Since the significant TST rate here was also very high, the investigation was extended to employees working in the next room, the dining room (circle 3), then to the rest of the staff (circle 4), and finally to some regular patrons who visited the establishment at least twice a month (circle 5).

Genotyping of the Mycobacterium tuberculosis strains found in the source case and his half-brother was ordered at the Quebec Public Health Laboratory. The strains were identical. The genotypic strain of a Mycobacterium tuberculosis from a pleural biopsy performed a few months earlier on a young Quebecker from the same town as the source case was also identical. However, no link could be established between this non-contagious case, the origin of which was still unknown, and previous cases except occasional visits to a pool hall. In light of this, the screening of nine employees of that pool hall, as well as 11 employees of another pool hall often frequented by the source case, was recommended. Only eight employees from the first pool hall were screened. There were no significant TST results (circle 6).

Table 1. TST results by circle

An investigation of hospital staff who had come into contact with the source case during the birth of his child and during the child's hospitalization in two regional hospitals before transfer to the children's hospital was conducted. Six of the 28 people screened at the first hospital had significant TST results, and one of these six was a recent conversion. At the second hospital, extended screening was performed on all staff that had worked in the units concerned. Seven of the 187 people screened had significant TST results, and two were known recent conversions.

Table 2. TST results by age group

The investigation took place over a 1-year period. It required a number of meetings between representatives of the public health department and the managers, owner and public relations firm of the establishment. Four employee information sessions were held in the weeks following the start of the investigation, and letters together with flyers on tuberculosis and the TST were handed out to all. The local Health Centre sent nursing staff to the establishment five times to conduct TSTs; those absent during these sessions were asked to come to the Health Centre. Individuals with significant TST results were sent a letter asking them to make an appointment at the same Health Centre's pneumology clinic. Of the 275 people targeted by the investigation, 236 took the screening test, for a participation rate of 86%. A specific investigation questionnaire revealed the types of contact that the regular patrons and all employees had had with the source case. Numerous phone calls had to be made to reach both the regular patrons and the employees working at the establishment during the investigation, as well as those who had left their employment in the previous 6 months. Numerous callbacks were also made to inform and encourage the few people who did not show up, mainly for the first TST, to be tested, with mixed results.

Note that the source case saw a doctor three times in the 5 months preceding the diagnosis. Based on the symptoms and on chest X-rays showing significant infiltrate, he was diagnosed with pneumonia each time and prescribed antibiotics. In 2002, the source case underwent surgery to remove a neck mass. The pathologist's diagnosis at that time was necrotizing granulomatous lymphadenitis. Neither direct examination nor cultures showed evidence of mycobacteria, and chest X-rays were normal.

Table 3. Description of the five cases of active tuberculosis

Conclusion

The large number of infected young Quebeckers in the contact group confirms that some cases of undiagnosed pulmonary tuberculosis could become highly contagious. This investigation has shown that tuberculosis, although rare in Quebec, must be considered in differential diagnoses for patients of all ages presenting with persistent cough, especially those originally from endemic regions such as the Caribbean, as well as for patients presenting with pneumonia who do not respond to antibiotics.

Acknowledgements

The Direction de santé publique des Laurentides would like to thank Françoise Claessens, Johanne Bourque and the entire nursing staff of the Health Centre. Their valuable collaboration facilitated the investigation by simplifying access to screening tests and referrals to the pneumology clinic when necessary. La Direction de santé publique des Laurentides would also like to thank the professionals at the Health Centre pneumology clinic, who quickly saw and evaluated most of the people who had a significant screening test. The authors would like to thank the following individuals, who collaborated in the investigation: Dr. Panagiota Macrisopoulos, Dr. Blandine Piquet-Gauthier, nurses Hélène Franc and Martine Barette, and Gilles Chaput, an information officer with the Direction de santé publique des Laurentides (QC).