RESEARCH ARTICLE
Excess Mortality Associated with Influenza among Tuberculosis Deaths in South Africa, 1999–2009 Sibongile Walaza1,4*, Cheryl Cohen1,4, Ananta Nanoo1, Adam L. Cohen2,3, Johanna McAnerney1, Claire von Mollendorf1,4, Jocelyn Moyes1,4, Stefano Tempia1,2,3* 1 National Institute for Communicable Diseases of the National Health Laboratory Service, Johannesburg, South Africa, 2 Influenza Division, Centers for Disease Control and Prevention, Atlanta, Georgia, United States of America, 3 Influenza Division, Centers for Disease Control and Prevention, Pretoria, South Africa, 4 Faculty of Health Sciences, University of the Witwatersrand, Johannesburg, South Africa * [email protected] (SW); [email protected] (ST)
Abstract Background
OPEN ACCESS Citation: Walaza S, Cohen C, Nanoo A, Cohen AL, McAnerney J, von Mollendorf C, et al. (2015) Excess Mortality Associated with Influenza among Tuberculosis Deaths in South Africa, 1999–2009. PLoS ONE 10(6): e0129173. doi:10.1371/journal. pone.0129173 Academic Editor: Katalin Andrea Wilkinson, University of Cape Town, SOUTH AFRICA Received: November 24, 2014
Published data on the interaction between influenza and pulmonary tuberculosis (PTB) are limited. We aimed to estimate the influenza-associated mortality among individuals with PTB in South Africa from 1999–2009.
Methods We modelled the excess influenza-associated mortality by applying Poisson regression models to monthly PTB and non-tuberculosis respiratory deaths, using laboratoryconfirmed influenza as a covariate.
Results
Data Availability Statement: All relevant data are within the paper.
PTB deaths increased each winter, coinciding with influenza virus circulation. Among individuals of any age, mean annual influenza-associated PTB mortality rate was 164/ 100,000 person-years (n = 439). The rate of non-tuberculosis respiratory deaths was 27/ 100,000 (n = 1125) for HIV-infected and 5/100,000 (n = 2367) for HIV-uninfected individuals of all ages. Among individuals aged 80% of TB-associated deaths were in individuals coinfected with HIV (Personal communication Cohen 2014), and HIV was a risk factor for influenzaassociated mortality [5–7]. To investigate whether the rate of influenza-associated mortality among PTB deaths was greater than expected simply as a result of underlying HIV infection, we compared the rate of influenza-associated mortality among PTB deaths to the rate
PLOS ONE | DOI:10.1371/journal.pone.0129173 June 15, 2015
2 / 12
Influenza-Associated Mortality in Tuberculosis
of influenza-associated mortality among non-tuberculosis respiratory deaths in HIV-infected and-uninfected individuals. In addition, we estimated the rates of influenza-associated mortality among PTB and non-tuberculosis respiratory deaths in individuals aged
Excess Mortality Associated with Influenza among Tuberculosis Deaths in South Africa, 1999–2009 Sibongile Walaza1,4*, Cheryl Cohen1,4, Ananta Nanoo1, Adam L. Cohen2,3, Johanna McAnerney1, Claire von Mollendorf1,4, Jocelyn Moyes1,4, Stefano Tempia1,2,3* 1 National Institute for Communicable Diseases of the National Health Laboratory Service, Johannesburg, South Africa, 2 Influenza Division, Centers for Disease Control and Prevention, Atlanta, Georgia, United States of America, 3 Influenza Division, Centers for Disease Control and Prevention, Pretoria, South Africa, 4 Faculty of Health Sciences, University of the Witwatersrand, Johannesburg, South Africa * [email protected] (SW); [email protected] (ST)
Abstract Background
OPEN ACCESS Citation: Walaza S, Cohen C, Nanoo A, Cohen AL, McAnerney J, von Mollendorf C, et al. (2015) Excess Mortality Associated with Influenza among Tuberculosis Deaths in South Africa, 1999–2009. PLoS ONE 10(6): e0129173. doi:10.1371/journal. pone.0129173 Academic Editor: Katalin Andrea Wilkinson, University of Cape Town, SOUTH AFRICA Received: November 24, 2014
Published data on the interaction between influenza and pulmonary tuberculosis (PTB) are limited. We aimed to estimate the influenza-associated mortality among individuals with PTB in South Africa from 1999–2009.
Methods We modelled the excess influenza-associated mortality by applying Poisson regression models to monthly PTB and non-tuberculosis respiratory deaths, using laboratoryconfirmed influenza as a covariate.
Results
Data Availability Statement: All relevant data are within the paper.
PTB deaths increased each winter, coinciding with influenza virus circulation. Among individuals of any age, mean annual influenza-associated PTB mortality rate was 164/ 100,000 person-years (n = 439). The rate of non-tuberculosis respiratory deaths was 27/ 100,000 (n = 1125) for HIV-infected and 5/100,000 (n = 2367) for HIV-uninfected individuals of all ages. Among individuals aged 80% of TB-associated deaths were in individuals coinfected with HIV (Personal communication Cohen 2014), and HIV was a risk factor for influenzaassociated mortality [5–7]. To investigate whether the rate of influenza-associated mortality among PTB deaths was greater than expected simply as a result of underlying HIV infection, we compared the rate of influenza-associated mortality among PTB deaths to the rate
PLOS ONE | DOI:10.1371/journal.pone.0129173 June 15, 2015
2 / 12
Influenza-Associated Mortality in Tuberculosis
of influenza-associated mortality among non-tuberculosis respiratory deaths in HIV-infected and-uninfected individuals. In addition, we estimated the rates of influenza-associated mortality among PTB and non-tuberculosis respiratory deaths in individuals aged
