Seasonal variations in tuberculosis diagnosis among HIV-positive individuals in Southern Africa: analysis of cohort studies at antiretroviral treatment programmes.

Ballif, Marie; Zürcher, Kathrin; Reid, Stewart E; Boulle, Andrew; Fox, Matthew P; Prozesky, Hans W; Chimbetete, Cleophas; Zwahlen, Marcel; Egger, Matthias; Fenner, Lukas; IeDEA-SA, Int DB to Evaluate AIDS in Southern Africa (2018). Seasonal variations in tuberculosis diagnosis among HIV-positive individuals in Southern Africa: analysis of cohort studies at antiretroviral treatment programmes. BMJ open, 8(1), e017405. BMJ Publishing Group 10.1136/bmjopen-2017-017405

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Seasonal variations in tuberculosis diagnoses have been attributed to seasonal climatic changes and indoor crowding during colder winter months. We investigated trends in pulmonary tuberculosis (PTB) diagnosis at antiretroviral therapy (ART) programmes in Southern Africa.


Five ART programmes participating in the International Epidemiology Database to Evaluate AIDS in South Africa, Zambia and Zimbabwe.


We analysed data of 331 634 HIV-positive adults (>15 years), who initiated ART between January 2004 and December 2014.


We calculated aggregated averages in monthly counts of PTB diagnoses and ART initiations. To account for time trends, we compared deviations of monthly event counts to yearly averages, and calculated correlation coefficients. We used multivariable regressions to assess associations between deviations of monthly ART initiation and PTB diagnosis counts from yearly averages, adjusted for monthly air temperatures and geographical latitude. As controls, we used Kaposi sarcoma and extrapulmonary tuberculosis (EPTB) diagnoses.


All programmes showed monthly variations in PTB diagnoses that paralleled fluctuations in ART initiations, with recurrent patterns across 2004-2014. The strongest drops in PTB diagnoses occurred in December, followed by April-May in Zimbabwe and South Africa. This corresponded to holiday seasons, when clinical activities are reduced. We observed little monthly variation in ART initiations and PTB diagnoses in Zambia. Correlation coefficients supported parallel trends in ART initiations and PTB diagnoses (correlation coefficient: 0.28, 95% CI 0.21 to 0.35, P<0.001). Monthly temperatures and latitude did not substantially change regression coefficients between ART initiations and PTB diagnoses. Trends in Kaposi sarcoma and EPTB diagnoses similarly followed changes in ART initiations throughout the year.


Monthly variations in PTB diagnosis at ART programmes in Southern Africa likely occurred regardless of seasonal variations in temperatures or latitude and reflected fluctuations in clinical activities and changes in health-seeking behaviour throughout the year, rather than climatic factors.

Item Type:

Journal Article (Original Article)


04 Faculty of Medicine > Pre-clinic Human Medicine > Institute of Social and Preventive Medicine (ISPM)
04 Faculty of Medicine > Department of Dermatology, Urology, Rheumatology, Nephrology, Osteoporosis (DURN) > Clinic of Rheumatology, Clinical Immunology and Allergology
04 Faculty of Medicine > Faculty Institutions > Teaching Staff, Faculty of Medicine

UniBE Contributor:

Ballif, Marie; Zürcher, Kathrin; Zwahlen, Marcel; Egger, Matthias and Fenner, Lukas


600 Technology > 610 Medicine & health
300 Social sciences, sociology & anthropology > 360 Social problems & social services




BMJ Publishing Group




Doris Kopp Heim

Date Deposited:

16 Jan 2018 09:32

Last Modified:

25 Oct 2019 04:42

Publisher DOI:


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PubMed ID:


Uncontrolled Keywords:

pulmonary tuberculosis seasonality south africa zambia zimbabwe




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