Tropical Medicine and Infectious Disease Article Tuberculosis as a Risk Factor for 1918 Influenza Pandemic Outcomes Svenn-Erik Mamelund 1,* and Jessica Dimka 2 1 Work Research Institute, OsloMet—Oslo Metropolitan University, PO. Box 4, St. Olavs Plass, 0130 Oslo, Norway 2 Department of Anthropology, University of Pittsburgh, Pittsburgh, PA 15260, USA;
[email protected] * Correspondence:
[email protected]; Tel.: +47-97100044 Received: 30 December 2018; Accepted: 26 April 2019; Published: 29 April 2019 Abstract: Tuberculosis (TB) mortality declined after the 1918 pandemic, suggesting that influenza killed those who would have died from TB. Few studies have analyzed TB as a direct risk factor for 1918 influenza morbidity and mortality by age and sex. We study the impacts of TB on influenza-like illness (% of population sick) and case fatality (% of cases dying) by age and sex through case-control comparisons of patients (N = 201) and employees (N = 97) from two Norwegian sanatoriums. Female patients, patients at Landeskogen sanatorium, and patients aged 10–39 years had significantly lower morbidity than the controls. None of the 62 sick employees died, while 15 of 84 sick patients did. The case-control difference in case fatality by sex was only significant for females at Lyster sanatorium and females at both sanatoriums combined. Non-significant case-control differences in case fatality for males were likely due to small samples. Patients 20–29 years for both sexes combined at Lyster sanatorium and at both sanatoriums combined, as well as females 20–29 years for both sanatoriums combined, had significantly higher case fatality. We conclude that TB was associated with higher case fatality, but morbidity was lower for patients than for employees.