Seasonal Variations in Notification of Active Tuberculosis Cases in China, 2005–2012

Abstract

BackgroundAlthough seasonal variation in tuberculosis (TB) incidence has been described in many countries, it remains unknown in China.MethodsA time series decomposition analysis (X-12-ARIMA) was performed to examine the seasonal variation in active TB cases nationwide from 2005 through 2012 in China. Seasonal amplitude was calculated for the evaluation of TB seasonal variation.ResultsA total of 7.78 million active TB cases were reported over a period of 8 years. A spring peak (April) was observed with seasonal amplitude of 46.3%, compared with the winter trough (February). Most cases in provinces with subtropical and tropical monsoon climate showed lower amplitudes than those in temperate continental, plateau and mountain climate regions. The magnitude of seasonality varied inversely with annual average temperature, r (95% CI) = -0.71 (-0.79, -0.61). The seasonal amplitudes were 56.7, 60.5, 40.6, 46.4 and 50.9% for patients aged ≤14, 15–24, 25–44, 45–64, and ≥65 years, respectively. Students demonstrated greater seasonal amplitude than peasants, migrant workers and workers (115.3% vs. 43.5, 41.6 and 48.1%). Patients with pulmonary TB had lower amplitude compared to patients with pleural and other extra-pulmonary TB (EPTB) (45.9% vs. 52.0 and 56.3%). Relapse cases with sputum smear positive TB (SS+ TB) had significantly higher seasonal amplitude compared to new cases with sputum smear positive TB (52.2% vs. 41.6%).ConclusionsTB is a seasonal disease in China. The peak and trough of TB transmission actually are in winter and in autumn respectively after factors of delay are removed. Higher amplitudes of TB seasonality are more likely to happen in temperate continental, plateau and mountain climate regions and regions with lower annual average temperature, and young person, students, patients with EPTB and relapse cases with SS+ TB are more likely to be affected by TB seasonality.

Seasonality of active tuberculosis notification from 2005 to 2014 in Xinjiang, China

“…The spring peak month was similar to the results from many other studies conducted in the northern hemisphere including those in India [10], Spain [11], Mongolia [12], China [13], the USA [14], Portugal [15], and the Netherlands [16]. The peak TB notification in South Africa [17] and Australia [18] was in October, which is the month of local spring in the southern hemisphere.…”

Spatial-temporal analysis of pulmonary tuberculosis in the northeast of the Yunnan province, People’s Republic of China

“…The possible reason of the symptom onset peak during the winter is a result of the reduction of exposure to ultraviolet rays from the sun and more indoor activities, which increases the possible susceptibility of people to infections with TB bacteria in the winter [21]. Similar trends in seasonal patterns had been reported elsewhere [22]. Resources should be distributed and planned for rationally in order to cope with the arrival of the incidence peak period and increase awareness-raising and running of focus groups during this period.…”

Seasonality of Tuberculosis in Delhi, India: A Time Series Analysis

“…Areas in the north India had the highest seasonal variation and low or no seasonality was noted in central and southern regions of India in that study. Seasonal variations have also been reported from various other countries like China [8] and United Kingdom [9]. Since seasons involve variations in various phenomena like temperature, humidity, precipitation, length of daylight, and so forth and also vary by geography and latitude, the presence of seasonal variation and the timing and magnitude of such seasonal variation may depend on some of these factors in ways not yet fully understood.…”