Nonlinear pattern of pulmonary tuberculosis among migrants at entry in Kuwait: 1997-2006

Seasonality of reported tuberculosis cases from 2006 to 2010 in Wuhan, China

We investigated the seasonality of tuberculosis (TB) in Wuhan, China, to evaluate the increased risk of disease transmission during each season and to develop an effective TB control strategy. We applied spectral analysis to the weekly prevalence data of sputum smear positive (SSP) and sputum smear negative (SSN) pulmonary TB reported from 2006 to 2010. Cases of both SSP and SSN feature 1·0- and 0·5-year periodic modes. The least squares method was used to fit curves to the two periodic modes for SSP and SSN data. The curves demonstrated dominant peaks in spring similar to cases reported previously for other locations. Notably for SSP, dominant peaks were also observed in summer. The spring peaks of SSP and SSN were explained in terms of poorly ventilated and humid rooms and vitamin D deficiency. For the summer peaks of SSP, summer influenza epidemics in Wuhan may contribute to the increase in TB prevalence.

Time series cross-correlation analysis of HIV seropositivity and pulmonary tuberculosis among migrants entering Kuwait

BACKGROUND

There is a paucity of published data on burden and pattern of dual infection with Mycobacterium tuberculosis and HIV among migrants from South Asia, South-east Asia and sub-Saharan Africa entering the Middle-East, particularly Kuwait. Therefore, this study assessed the overall prevalence of HIV infection and pulmonary tuberculosis (TB) and evaluated the ecological relationship between them.

METHODS

Time series cross-correlation analysis was used to determine the ecological time-lagged relationship between the monthly proportions (per 100,000) of HIV seropositive and pulmonary TB cases among migrant workers that entered Kuwait between January 1, 1997 and December 31, 2006.

RESULTS

During the study period, overall prevalence (per 100,000) of HIV seropositivity and pulmonary TB among the migrants was 21 (494/23,28,582) (95% CI: 19-23), and 198 (4608/23,28,582) (95% CI: 192-204), respectively. Estimated cross-correlation function revealed a significant positive correlation (0.292±0.093) at lag -3 representing a positive relationship between the proportions of HIV seropositive (per 100,000) migrants tested 3 months earlier and the proportion of pulmonary TB (per 100,000) cases detected among migrants in a given month. Thus, the peak in proportion of pulmonary TB cases preceded the peak in proportion of HIV seropositive migrants indicating a direct time-lagged association between HIV seropositivity and the prevalence of pulmonary TB among migrants.

CONCLUSIONS

HIV infection seemed to have played a significant role in the re-activation of latent M. tuberculosis infection in this migrant population. While currently less evident, in near future, however, TB and HIV/AIDS control programmes in the countries of origin of migrants may face a crucial challenge. Knowledge of serious consequences of association between HIV infection and pulmonary TB allows the promotion of public heath education to reduce the exposure to these infections. Future studies may focus on evaluating the impact of public health education programs on this dual burden of HIV infection and pulmonary TB in migrants.

Health aspects of the pre-departure phase of migration

In the second article in a six-part PLoS Medicine series on Migration & Health, Brian Gushulak and Douglas MacPherson discuss the pre-departure phase of migration and the specific health risks and policy needs associated with this phase.