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Free Content Seasonality of tuberculosis in New York City, 1990–2007

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SETTING: Several non-US-based studies have found seasonal fluctuations in the incidence of tuberculosis (TB).

OBJECTIVE: The current study examined patterns of TB seasonality for New York City verified TB cases from January 1990 to December 2007.

DESIGN: Autocorrelation functions and Fourier analysis were used to detect a cyclical pattern in monthly incidence rates. Analysis of variance was used to compare seasonal mean case proportions.

RESULTS: A cyclical pattern was detected every 12 months. Of the 34 004 TB cases included, 21.9% were in the fall (September–November), 24.7% in winter (December–February), 27.3% in spring (March–May), and 26.1% in the summer (June–August). The proportion of cases was lowest in fall (P < 0.0001) and highest in the spring (P < 0.0002).

CONCLUSION: Possible explanations for seasonal variations in TB incidence include lower vitamin D levels in winter, leading to immune suppression and subsequent reactivation of latent TB; indoor winter crowding, increasing the likelihood of TB transmission; and providers attributing TB symptoms to other respiratory illnesses in winter, resulting in a delay in TB diagnosis until spring. Understanding TB seasonality may help TB programs better plan and allocate resources for TB control activities.

Keywords: New York City; seasonal variation; statistical models; trends; tuberculosis

Document Type: Research Article


Affiliations: 1: New York City Department of Mental Health and Hygiene, New York, New York, USA; and Department of Epidemiology, Surveillance Concentration, Columbia University Mailman School of Public Health, New York, New York, USA 2: New York City Department of Mental Health and Hygiene, New York, New York, USA

Publication date: 2012-01-01

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  • The International Journal of Tuberculosis and Lung Disease publishes articles on all aspects of lung health, including public health-related issues such as training programmes, cost-benefit analysis, legislation, epidemiology, intervention studies and health systems research. The IJTLD is dedicated to the continuing education of physicians and health personnel and the dissemination of information on tuberculosis and lung health world-wide.

    Certain IJTLD articles are selected for translation into French, Spanish, Chinese or Russian. They are available on the Union website

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