Aim: To describe a secondary school outbreak of tuberculosis in Palmerston North, New Zealand in 2006.
Methods: Case and contact management was conducted by MidCentral District Health Board according to national guidelines.
Results: The index (and source) case was a school student. Delayed diagnosis led to extensive transmission. Contact investigation detected fifteen secondary cases, from six of whom Mycobacterium tuberculosis organism was cultured which was identical to that found in the index case. Latent tuberculosis infection was diagnosed in 235 of 1828 contacts. Following logistic regression, risk of infection was significantly associated with age, exposure setting (household and school vs other settings) and duration of exposure. Large numbers of contacts were infected who had no known contact with the index case, thus indicating probable tertiary transmission from the 7 infectious secondary cases. The secondary healthcare cost of the outbreak was estimated at $279,481. Findings from school tuberculosis (TB) outbreaks since 1990 are summarised.
Conclusion: This was the largest tuberculosis outbreak described in New Zealand and one of the largest school outbreaks reported in the published literature.