Seasonality in various forms of tuberculosis

Abstract

Setting: Newly notified cases of tuberculosis (TB) for 5 years (1998 and 2000-2003) in Japan.

Objective: To study the seasonality of notification for various forms of TB.

Design: Descriptive analyses of newly notified cases by month of the year. Seasonal variations were compared among various forms of TB.

Results: In almost all the forms of TB examined, the numbers of newly notified TB cases were the lowest from November to January. For childhood and pleural TB, the numbers of cases of TB were highest from March to May (spring) and from April to June (spring to early summer), respectively. For sputum smear-positive pulmonary tuberculosis (PTB) in the young, the number of cases was also highest from March to May. For lymph node TB (except mediastinal) and sputum smear-positive PTB in the elderly (aged > or =50 years), the numbers of cases were highest from May to July (late spring to summer) and from June to August (summer), respectively.

Conclusion: The seasonality of TB notification differs for the various forms of TB, which may reflect differences in the seasonality of clinical development of different types of TB disease such as primary, early and late post-primary TB.