Abstract
BackgroundTuberculosis (TB) is a major global health burden, with an estimated quarter of the world’s population being infected. The World Health Organization (WHO) launched the “End TB Strategy” in 2014 emphasising knowing the epidemic. WHO ranks Vietnam 12th in the world of high burden countries.TB spatial and temporal patterns have been observed globally with evidence of Vitamin D playing a role in seasonality. We explored the presence of temporal and spatial clustering of TB in Vietnam and their determinants to aid public health measures.MethodsData were collected by the National TB program of Vietnam from 2010 to 2015 and linked to the following datasets: socio-demographic characteristics; climatic variables; influenza-like-illness (ILI) incidence; geospatial data. The TB dataset was aggregated by province and quarter. Descriptive time series analyses using LOESS regression were completed per province to determine seasonality and trend. Harmonic regression was used to determine the amplitude of seasonality by province.A mixed-effect linear model was used with province and year as random effects and all other variables as fixed effects.ResultsThere were 610,676 cases of TB notified between 2010 and 2015 in Vietnam. Heat maps of TB incidence per quarter per province showed substantial temporal and geospatial variation. Time series analysis demonstrated seasonality throughout the country, with peaks in spring/summer and troughs in autumn/winter. Incidence was consistently higher in the south, the three provinces with the highest incidence per 100,000 population were Tay Ninh, An Giang and Ho Chi Minh City. However, relative seasonal amplitude was more pronounced in the north.Mixed-effect linear model confirmed that TB incidence was associated with time and latitude. Of the demographic, socio-economic and health related variables, population density, percentage of those under 15 years of age, and HIV infection prevalence per province were associated with TB incidence. Of the climate variables, absolute humidity, average temperature and sunlight were associated with TB incidence.ConclusionPreventative public health measures should be focused in the south of Viet Nam where incidence is highest. Vitamin D is unlikely to be a strong driver of seasonality but supplementation may play a role in a package of interventions.
Highlights
Tuberculosis (TB) is a major global health burden, with an estimated quarter of the world’s population being infected
Preventative public health measures should be focused in the south of Viet Nam where incidence is highest
Vitamin D is unlikely to be a strong driver of seasonality but supplementation may play a role in a package of interventions
Summary
Tuberculosis (TB) is a major global health burden, with an estimated quarter of the world’s population being infected. WHO ranks Vietnam 12th in the world of high burden countries. TB in Vietnam causes a high burden of disease, with an estimated annual incidence of 129 per 100,000 population [4]. Socio-economic factors, poor health system development and scarcity of medical care have been linked with increased risk of TB on individual and population levels in Asia [5, 6]. These variables alone cannot explain the seasonality of TB incidence, which has been documented in many areas of the world. Almost all studies assessing seasonality demonstrate a peak in spring/summer and a trough in autumn/winter, which is the opposite to other respiratory infections [7,8,9,10,11]
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