Abstract
BackgroundPublished 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.MethodsWe modelled the excess influenza-associated mortality by applying Poisson regression models to monthly PTB and non-tuberculosis respiratory deaths, using laboratory-confirmed influenza as a covariate.ResultsPTB 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 <65 years, influenza-associated PTB mortality risk was elevated compared to influenza-associated non-tuberculosis respiratory deaths in HIV-infected (relative risk (RR): 5.2; 95% CI: 4.6–5.9) and HIV-uninfected individuals (RR: 61.0; CI: 41.4–91.0). Among individuals aged ≥65 years, influenza-associated PTB mortality risk was elevated compared to influenza-associated non-tuberculosis respiratory deaths in HIV-uninfected individuals (RR: 13.0; 95% CI: 12.0–14.0).ConclusionWe observed an increased risk of influenza-associated mortality in persons with PTB compared to non-tuberculosis respiratory deaths. If confirmed in other settings, our findings may support recommendations for active inclusion of patients with TB for influenza vaccination and empiric influenza anti-viral treatment of patients with TB during influenza epidemics.
Highlights
In 2010, there were an estimated 8.8 million incident cases of tuberculosis globally [1]
Among individuals aged
Among individuals aged 65 years, influenza-associated PTB mortality risk was elevated compared to influenza-associated non-tuberculosis respiratory deaths in HIVuninfected individuals (RR: 13.0; 95% CI: 12.0–14.0)
Summary
In 2010, there were an estimated 8.8 million incident cases of tuberculosis globally [1]. HIV is the most important risk factor for tuberculosis disease in South Africa. In South Africa, there were an estimated 390,000 incident cases of tuberculosis in 2011 of which 65% were co-infected with HIV [2]. It is estimated that annual influenza epidemics result in three to five million cases of severe illness, and 250,000–500,000 deaths [3]. In 2010 in South Africa, after tuberculosis, pneumonia and influenza was the second leading underlying natural cause of death [4]. HIV infection is an important risk factor for influenza–associated mortality. We aimed to estimate the influenza-associated mortality among individuals with PTB in South Africa from 1999–2009
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