Smear-Positive Tuberculosis in a School Bus Driver
A 41-year-old man who drives a school bus carrying 60 children was diagnosed five days ago with smear-positive pulmonary tuberculosis (3+ acid-fast bacilli, cavitary right upper lobe). He began rifampicin, isoniazid, pyrazinamide and ethambutol under directly observed therapy yesterday and is in his first week of treatment. He lives in a three-bedroom flat with his wife, two children aged 6 and 9, his brother who is on haemodialysis, and a cousin. He shares driving duties on alternate days with one other driver and coaches a children's football team on Saturdays. He feels well, has no cough now, and asks whether he can return to work on Monday because he cannot afford unpaid leave. He has not told his employer the diagnosis and asks you not to.
1. How would you prioritise contact investigation in this cluster, and what does the window period mean for interpreting tests done this week?
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Prioritise by infectiousness plus the host's risk of progressing to disease.
- Household contacts, especially the brother on haemodialysis. Dialysis patients are immunosuppressed and have among the highest rates of progression from latent to active tuberculosis. He is first in line, and screening must include a chest radiograph, not just an interferon-gamma release assay.
- The children aged 6 and 9. Young children have a high risk of rapid progression and of disseminated or meningeal disease, and they may have been infected recently.
- The alternate bus driver. Prolonged, repeated exposure in an enclosed cab is a genuine close contact.
- The school children on his route. A large, ventilated vehicle with short trips makes these lower-risk casual contacts, but duration, window closure and crowding must be assessed route by route; public health should decide, using a structured exposure assessment, whether whole-bus screening is warranted.
- The football team. Outdoor contact is lowest risk, but shared changing rooms and travel need to be considered.
Window period: an interferon-gamma release assay or tuberculin skin test takes roughly 2 to 8 weeks after infection to become positive. A negative test this week does not exclude infection. Take a baseline test now to identify those already infected, then repeat at about 8 weeks after the last exposure. Everyone also needs an active-disease symptom screen and, for high-risk contacts, a chest radiograph, because preventive therapy must never be given while active disease is possible.
2. He asks you to keep the diagnosis from his employer. How do you handle confidentiality, work exclusion and the practical pressures he is facing?
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Start with his situation, not with the rule. He is frightened about income, not being difficult. Say plainly that he cannot drive children while he is smear-positive and coughing, and that this is temporary and treatable.
Confidentiality is not absolute but it is not the nurse's to breach casually. The nurse should not telephone the employer and disclose the diagnosis. The correct route is statutory notification to the public health tuberculosis programme by the treating physician; the programme then conducts contact tracing and advises on exclusion from work, usually without naming the index case to the wider workplace. Explain to him what will be shared, with whom and why, and seek his agreement to a minimal disclosure - for example, that he is under treatment for a respiratory infection and is being followed up by public health.
Work exclusion criteria: for drug-susceptible pulmonary tuberculosis, exclusion typically continues until he has had at least two weeks of effective therapy, is clinically improving, and has consecutive negative sputum smears (programmes vary, so confirm local policy). He started treatment yesterday, so Monday is too early. Ask the occupational health service and public health to issue the exclusion letter and to state the criteria for return, so the decision is carried by an authority rather than by the nurse.
Practical support: involve the social worker about sick leave, statutory sick pay or benefits, and reassure him that directly observed therapy can be delivered near home or work. If he refuses to cooperate and intends to drive anyway, escalate to the treating physician and the public health officer - the legal duty to protect contacts rests with them.
3. Which contacts should be offered preventive therapy, and what else must be arranged for this household?
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Principle: preventive therapy is offered to contacts with evidence of latent infection once active disease has been excluded. In many national programmes, household children under 5 are treated presumptively even before test results, because the risk of rapid progression outweighs the risk of a short course of treatment.
Applying it here
- Children aged 6 and 9: symptom screen and chest radiograph first. If active disease is excluded and the interferon-gamma release assay is positive at baseline or at 8 weeks, offer latent tuberculosis treatment (usually 3 months of weekly isoniazid plus rifapentine, or 6 months of isoniazid, per local protocol). If either child has symptoms, weight loss, or a abnormal radiograph, they move onto the active-disease pathway instead, with gastric aspirate or sputum testing.
- Brother on haemodialysis: highest progression risk. Chest radiograph and assay now, active disease excluded, then latent treatment with careful attention to drug interactions and dialysis timing; coordinate with the renal team.
- Wife and cousin: screen; treat latent infection if positive.
- The co-driver is screened through the public health contact investigation, not by the ward nurse.
Household arrangements: offer HIV testing to the index case and to contacts (a major driver of progression), review the index case's drug interactions and baseline liver function, assess crowding and ventilation in a three-bedroom flat with five adults and two children, arrange directly observed therapy and a treatment supporter, and give written information in the household's first language. Record consent and refusals carefully.