Tuberculosis (TB) is caused by infection with the pathogen Mycobacterium tuberculosis
]. A recent World Health Organization (WHO) report documented the diagnosis of nearly 10 million new cases of TB in 2007 with an estimated 1.3 million deaths from TB in the same year [2
]. Therefore, TB remains a leading cause of death resulting in high morbidity and mortality worldwide, with an estimate of one-third of world's population is infected with TB bacilli [2
]. On the basis of these statistics, TB is among the top ten causes of death worldwide. Despite predictions of a decline in global incidence, the number of new cases is continuous to grow.
Over 50% of global TB cases are found in Southeastern Asia and the Western Pacific [2
]. The TB incidence and mortality rates in Taiwan varied geographically, with higher rates in southern and eastern regions than in the northern region [3
]. The epidemiological study in Taiwan found that incidence and mortality rate of TB infection were 62.0-74.6 (per 100,000 population) and 3.3-5.7 (per 100,000 per population) in the period 2002-2008, respectively [4
]. The notification rate and mortality rate were higher in eastern Taiwan than in the national scale [5
]. Hsueh et al. [3
] found that aborigines and people living in mountainous regions in eastern Taiwan had higher incidence rates.
Hsueh et al. [3
] and Lee et al. [4
] implicated that high disease burden of TB and inadequate current control infrastructure and training for TB implementation, e.g., directly observed treatment short-course (DOTS) strategy, are posing a great impact on public health in Taiwan, leading to current challenges to TB control such as the increasing burden of patients with multidrug-resistant TB infection, the persistent high rate of mortality, and unsatisfactory compliance of treatment.
Previous studies have reported a strong association between seasonality and TB in temperate, tropical, and subtropical regions [6
]. They found that seasonal peaks of TB cases generally occurred at the end of winter [9
] and at the beginning of the summer season [7
]. They implicated that increased indoor exposure in winter, diagnostic delays, and an association with vitamin D levels explained this phenomenon [6
]. There are strong interactions between the effects of seasonality and the effects of weather because seasonality might influence the season of emergence of active TB, making both sensitive to additional stresses such as climate change. Little is known about the time-series dynamics of TB trends in Taiwan taking into account seasonal patterns and weather effects.
Dye and Williams [15
] have characterized the impact of key demographic and epidemiological factors on TB trends including (i
) epidemiological differences among populations because some infected people are at high risk of developing active TB and some kinds of people and patients transmit more infections than others, (ii
) demographic transition because populations are aging and a relatively high risk of TB among the elderly is a real possibility, and (iii
) rejuvenation of the TB epidemic among young adults.
It is believed that by understanding the factors that affect TB trends will help to make control programs more successful. Despite this far-reaching importance, empirical estimates of long-term trends in TB epidemics in Taiwan remain limited. On the other hand, despite differences in scale and approach, it is clear that long-term estimates of TB trends are a necessary. The purpose of this study was to assess the characteristics of TB trends from 2004-2008 in Taiwan by month, year, gender, age, temperature, seasonality, aborigines/nonaborigines and to provide pronounced generalized regression models to examine the potential predictors for the monthly TB incidence in regional and national scales.