Tuberculosis case notifications in Malawi have strong seasonal and weather-related trends

Abstract Seasonal trends in tuberculosis (TB) notifications have been observed in several countries but are poorly understood. Explanatory factors may include weather, indoor crowding, seasonal respiratory infections and migration. Using enhanced citywide TB surveillance data collected over nine yea...

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Autores principales:	Amir Kirolos, Deus Thindwa, McEwen Khundi, Rachael M. Burke, Marc Y. R. Henrion, Itaru Nakamura, Titus H. Divala, Marriott Nliwasa, Elizabeth L. Corbett, Peter MacPherson
Formato:	article
Lenguaje:	EN
Publicado:	Nature Portfolio 2021
Materias:	Medicine R Science Q
Acceso en línea:	https://doaj.org/article/d2bcea411d0c4a48afaa64c7f6faae63
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spelling	oai:doaj.org-article:d2bcea411d0c4a48afaa64c7f6faae632021-12-02T11:37:27ZTuberculosis case notifications in Malawi have strong seasonal and weather-related trends10.1038/s41598-021-84124-w2045-2322https://doaj.org/article/d2bcea411d0c4a48afaa64c7f6faae632021-02-01T00:00:00Zhttps://doi.org/10.1038/s41598-021-84124-whttps://doaj.org/toc/2045-2322Abstract Seasonal trends in tuberculosis (TB) notifications have been observed in several countries but are poorly understood. Explanatory factors may include weather, indoor crowding, seasonal respiratory infections and migration. Using enhanced citywide TB surveillance data collected over nine years in Blantyre, Malawi, we set out to investigate how weather and seasonality affect temporal trends in TB case notification rates (CNRs) across different demographic groups. We used data from prospective enhanced surveillance between April 2011 and December 2018, which systematically collected age, HIV status, sex and case notification dates for all registering TB cases in Blantyre. We retrieved temperature and rainfall data from the Global Surface Summary of the Day weather station database. We calculated weekly trends in TB CNRs, rainfall and temperature, and calculated 10-week moving averages. To investigate the associations between rainfall, temperature and TB CNRs, we fitted generalized linear models using a distributed lag nonlinear framework. The estimated Blantyre population increased from 1,068,151 in April 2011 to 1,264,304 in December 2018, with 15,908 TB cases recorded. Overall annual TB CNRs declined from 222 to 145 per 100,000 between 2012 and 2018, with the largest declines seen in HIV-positive people and adults aged over 20 years old. TB CNRs peaks occurred with increasing temperature in September and October before the onset of increased rainfall, and later in the rainy season during January-March, after sustained rainfall. When lag between a change in weather and TB case notifications was accounted for, higher average rainfall was associated with an equivalent six weeks of relatively lower TB notification rates, whereas there were no changes in TB CNR associated with change in average temperatures. TB CNRs in Blantyre have a seasonal pattern of two cyclical peaks per year, coinciding with the start and end of the rainy season. These trends may be explained by increased transmission at certain times of the year, by limited healthcare access, by patterns of seasonal respiratory infections precipitating cough and care-seeking, or by migratory patterns related to planting and harvesting during the rainy season.Amir KirolosDeus ThindwaMcEwen KhundiRachael M. BurkeMarc Y. R. HenrionItaru NakamuraTitus H. DivalaMarriott NliwasaElizabeth L. CorbettPeter MacPhersonNature PortfolioarticleMedicineRScienceQENScientific Reports, Vol 11, Iss 1, Pp 1-9 (2021)
institution	DOAJ
collection	DOAJ
language	EN
topic	Medicine R Science Q
spellingShingle	Medicine R Science Q Amir Kirolos Deus Thindwa McEwen Khundi Rachael M. Burke Marc Y. R. Henrion Itaru Nakamura Titus H. Divala Marriott Nliwasa Elizabeth L. Corbett Peter MacPherson Tuberculosis case notifications in Malawi have strong seasonal and weather-related trends
description	Abstract Seasonal trends in tuberculosis (TB) notifications have been observed in several countries but are poorly understood. Explanatory factors may include weather, indoor crowding, seasonal respiratory infections and migration. Using enhanced citywide TB surveillance data collected over nine years in Blantyre, Malawi, we set out to investigate how weather and seasonality affect temporal trends in TB case notification rates (CNRs) across different demographic groups. We used data from prospective enhanced surveillance between April 2011 and December 2018, which systematically collected age, HIV status, sex and case notification dates for all registering TB cases in Blantyre. We retrieved temperature and rainfall data from the Global Surface Summary of the Day weather station database. We calculated weekly trends in TB CNRs, rainfall and temperature, and calculated 10-week moving averages. To investigate the associations between rainfall, temperature and TB CNRs, we fitted generalized linear models using a distributed lag nonlinear framework. The estimated Blantyre population increased from 1,068,151 in April 2011 to 1,264,304 in December 2018, with 15,908 TB cases recorded. Overall annual TB CNRs declined from 222 to 145 per 100,000 between 2012 and 2018, with the largest declines seen in HIV-positive people and adults aged over 20 years old. TB CNRs peaks occurred with increasing temperature in September and October before the onset of increased rainfall, and later in the rainy season during January-March, after sustained rainfall. When lag between a change in weather and TB case notifications was accounted for, higher average rainfall was associated with an equivalent six weeks of relatively lower TB notification rates, whereas there were no changes in TB CNR associated with change in average temperatures. TB CNRs in Blantyre have a seasonal pattern of two cyclical peaks per year, coinciding with the start and end of the rainy season. These trends may be explained by increased transmission at certain times of the year, by limited healthcare access, by patterns of seasonal respiratory infections precipitating cough and care-seeking, or by migratory patterns related to planting and harvesting during the rainy season.
format	article
author	Amir Kirolos Deus Thindwa McEwen Khundi Rachael M. Burke Marc Y. R. Henrion Itaru Nakamura Titus H. Divala Marriott Nliwasa Elizabeth L. Corbett Peter MacPherson
author_facet	Amir Kirolos Deus Thindwa McEwen Khundi Rachael M. Burke Marc Y. R. Henrion Itaru Nakamura Titus H. Divala Marriott Nliwasa Elizabeth L. Corbett Peter MacPherson
author_sort	Amir Kirolos
title	Tuberculosis case notifications in Malawi have strong seasonal and weather-related trends
title_short	Tuberculosis case notifications in Malawi have strong seasonal and weather-related trends
title_full	Tuberculosis case notifications in Malawi have strong seasonal and weather-related trends
title_fullStr	Tuberculosis case notifications in Malawi have strong seasonal and weather-related trends
title_full_unstemmed	Tuberculosis case notifications in Malawi have strong seasonal and weather-related trends
title_sort	tuberculosis case notifications in malawi have strong seasonal and weather-related trends
publisher	Nature Portfolio
publishDate	2021
url	https://doaj.org/article/d2bcea411d0c4a48afaa64c7f6faae63
work_keys_str_mv	AT amirkirolos tuberculosiscasenotificationsinmalawihavestrongseasonalandweatherrelatedtrends AT deusthindwa tuberculosiscasenotificationsinmalawihavestrongseasonalandweatherrelatedtrends AT mcewenkhundi tuberculosiscasenotificationsinmalawihavestrongseasonalandweatherrelatedtrends AT rachaelmburke tuberculosiscasenotificationsinmalawihavestrongseasonalandweatherrelatedtrends AT marcyrhenrion tuberculosiscasenotificationsinmalawihavestrongseasonalandweatherrelatedtrends AT itarunakamura tuberculosiscasenotificationsinmalawihavestrongseasonalandweatherrelatedtrends AT titushdivala tuberculosiscasenotificationsinmalawihavestrongseasonalandweatherrelatedtrends AT marriottnliwasa tuberculosiscasenotificationsinmalawihavestrongseasonalandweatherrelatedtrends AT elizabethlcorbett tuberculosiscasenotificationsinmalawihavestrongseasonalandweatherrelatedtrends AT petermacpherson tuberculosiscasenotificationsinmalawihavestrongseasonalandweatherrelatedtrends
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Tuberculosis case notifications in Malawi have strong seasonal and weather-related trends

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