Tuberculosis as a Risk Factor for 1918 Influenza Pandemic Outcomes

Frailty and survival in the 1918 influenza pandemic

One of the most well-known yet least understood aspects of the 1918 influenza pandemic is the disproportionately high mortality among young adults. Contemporary accounts further describe the victims as healthy young adults, which is contrary to the understanding of selective mortality, which posits that individuals with the highest frailty within a group are at the greatest risk of death. We use a bioarchaeological approach, combining individual-level information on health and stress gleaned from the skeletal remains of individuals who died in 1918 to determine whether healthy individuals were dying during the 1918 pandemic or whether underlying frailty contributed to an increased risk of mortality. Skeletal data on tibial periosteal new bone formation were obtained from 369 individuals from the Hamann-Todd documented osteological collection in Cleveland, Ohio. Skeletal data were analyzed alongside known age at death using Kaplan-Meier survival and Cox proportional hazards analysis. The results suggest that frail or unhealthy individuals were more likely to die during the pandemic than those who were not frail. During the flu, the estimated hazards for individuals with periosteal lesions that were active at the time of death were over two times higher compared to the control group. The results contradict prior assumptions about selective mortality during the 1918 influenza pandemic. Even among young adults, not everyone was equally likely to die-those with evidence of systemic stress suffered greater mortality. These findings provide time depth to our understanding of how variation in life experiences can impact morbidity and mortality even during a pandemic caused by a novel pathogen.

Differences in hospitalizations associated with severe COVID-19 disease among foreign- and Swedish-born

BACKGROUND

Differences in pre-existing health conditions are hypothesized to explain immigrants' excess COVID-19 mortality compared to natives. In this study, we evaluate whether immigrants residing in Sweden before the outbreak were more likely to be hospitalized for conditions associated with severe COVID-19 disease.

METHODS

A cohort study using population-register data was conducted with follow-up between 1 January 1997 and 31 December 2017. Poisson regression was fitted to estimate incidence rate ratio (RR) and 95% confident intervals (95% CI) for 10 causes of hospitalization.

RESULTS

Compared to Swedish-born individuals, most immigrant groups showed a decreased risk of hospitalization for respiratory chronic conditions, CVD, cancer, chronic liver conditions and neurological problems. All immigrant groups had increased risk of hospitalization for tuberculosis [RR between 88.49 (95% CI 77.21; 101.40) for the Horn of Africa and 1.69 (95% CI 1.11; 2.58) for North America], HIV [RR between 33.23 (95% CI 25.17; 43.88) for the rest of Africa and 1.31 (95% CI 0.93; 1.83) for the Middle East] and, with a few exceptions, also for chronic kidney conditions, diabetes and thalassemia.

CONCLUSIONS

Foreign-born individuals-including origins with excess COVID-19 mortality in Sweden-did not show increased risk of hospitalizations for most causes associated with severe COVID-19 disease. However, all groups showed increased risks of hospitalization for tuberculosis and HIV and, with exceptions, for chronic kidney conditions, diabetes and thalassemia. Although studies should determine whether these health conditions explain the observed excess COVID-19 mortality, our study alerts to an increased risk of hospitalization that can be avoidable via treatment or preventive measures.

Unequal excess mortality during the Spanish Flu pandemic in the Netherlands

A century after the Spanish Flu, the COVID-19 pandemic has brought renewed attention to socioeconomic and occupational differences in mortality in the earlier pandemic. The magnitude of these differences and the pathways between occupation and increased mortality remain unclear, however. In this paper, we explore the relation between occupational characteristics and excess mortality among men during the Spanish Flu pandemic in the Netherlands. By creating a new occupational coding for exposure to disease at work, we separate social status and occupational conditions for viral transmission. We use a new data set based on men's death certificates to calculate excess mortality rates by region, age group, and occupational group. Using OLS regression models, we estimate whether social position, regular interaction in the workplace, and working in an enclosed space affected excess mortality among men in the Netherlands in the autumn of 1918. We find some evidence that men with occupations that featured high levels of social contact had higher mortality in this period. Above all, however, we find a strong socioeconomic gradient to excess mortality among men during the Spanish Flu pandemic, even after accounting for exposure in the workplace.

Biocultural perspectives of infectious diseases and demographic evolution: Tuberculosis and its comorbidities through history

Anthropologists recognize the importance of conceptualizing health in the context of the mutually evolving nature of biology and culture through the biocultural approach, but biocultural anthropological perspectives of infectious diseases and their impacts on humans (and vice versa) through time are relatively underrepresented. Tuberculosis (TB) has been a constant companion of humans for thousands of years and has heavily influenced population health in almost every phase of cultural and demographic evolution. TB in human populations has been dramatically influenced by behavior, demographic and epidemiological shifts, and other comorbidities through history. This paper critically discusses TB and some of its major comorbidities through history within a biocultural framework to show how transitions in human demography and culture affected the disease-scape of TB. In doing so, I address the potential synthesis of biocultural and epidemiological transition theory to better comprehend the mutual evolution of infectious diseases and humans.

Pandemics, past and present: The role of biological anthropology in interdisciplinary pandemic studies

Biological anthropologists are ideally suited for the study of pandemics given their strengths in human biology, health, culture, and behavior, yet pandemics have historically not been a major focus of research. The COVID‐19 pandemic has reinforced the need to understand pandemic causes and unequal consequences at multiple levels. Insights from past pandemics can strengthen the knowledge base and inform the study of current and future pandemics through an anthropological lens. In this paper, we discuss the distinctive social and epidemiological features of pandemics, as well as the ways in which biological anthropologists have previously studied infectious diseases, epidemics, and pandemics. We then review interdisciplinary research on three pandemics–1918 influenza, 2009 influenza, and COVID‐19–focusing on persistent social inequalities in morbidity and mortality related to sex and gender; race, ethnicity, and Indigeneity; and pre‐existing health and disability. Following this review of the current state of pandemic research on these topics, we conclude with a discussion of ways biological anthropologists can contribute to this field moving forward. Biological anthropologists can add rich historical and cross‐cultural depth to the study of pandemics, provide insights into the biosocial complexities of pandemics using the theory of syndemics, investigate the social and health impacts of stress and stigma, and address important methodological and ethical issues. As COVID‐19 is unlikely to be the last global pandemic, stronger involvement of biological anthropology in pandemic studies and public health policy and research is vital.

Not the great equalizers: Covid-19, 1918-20 influenza, and the need for a paradigm shift in pandemic preparedness

Despite common perceptions to the contrary, pandemic diseases do not affect populations indiscriminately. In this paper, we review literature produced by demographers, historians, epidemiologists, and other researchers on disparities during the 1918-20 influenza pandemic and the Covid-19 pandemic. Evidence from these studies demonstrates that lower socio-economic status and minority/stigmatized race or ethnicity are associated with higher morbidity and mortality. However, such research often lacks theoretical frameworks or appropriate data to explain the mechanisms underlying these disparities fully. We suggest using a framework that considers proximal and distal factors contributing to differential exposure, susceptibility, and consequences as one way to move this research forward. Further, current pandemic preparedness plans emphasize medically defined risk groups and epidemiological approaches. Therefore, we conclude by arguing in favour of a transdisciplinary paradigm that recognizes socially defined risk groups, includes input from the social sciences and humanities and other diverse perspectives, and contributes to the reduction of health disparities before a pandemic hits.

Syndemics and the history of disease: Towards a new engagement

Historians of medicine and disease have yet to think through a syndemic lens. This commentary aims to point out why they should. Although there are several hurdles to overcome, our histories of disease and our understanding of current syndemics both stand to gain should historians begin to explore episodes of cooccurring diseases that share root causes.

The association between socioeconomic status and pandemic influenza: Systematic review and meta-analysis

BACKGROUND

The objective of this study is to document whether and to what extent there is an association between socioeconomic status (SES) and disease outcomes in the last five influenza pandemics.

METHODS/PRINCIPLE FINDINGS

The review included studies published in English, Danish, Norwegian and Swedish. Records were identified through systematic literature searches in six databases. We summarized results narratively and through meta-analytic strategies. Only studies for the 1918 and 2009 pandemics were identified. Of 14 studies on the 2009 pandemic including data on both medical and social risk factors, after controlling for medical risk factors 8 demonstrated independent impact of SES. In the random effect analysis of 46 estimates from 35 studies we found a pooled mean odds ratio of 1.4 (95% CI: 1.2-1.7, p < 0.001), comparing the lowest to the highest SES, but with substantial effect heterogeneity across studies,-reflecting differences in outcome measures and definitions of case and control samples. Analyses by pandemic period (1918 or 2009) and by level of SES measure (individual or ecological) indicated no differences along these dimensions. Studies using healthy controls tended to document that low SES was associated with worse influenza outcome, and studies using infected controls find low SES associated with more severe outcomes. A few studies compared severe outcomes (ICU or death) to hospital admissions but these did not find significant SES associations in any direction. Studies with more unusual comparisons (e.g., pandemic vs seasonal influenza, seasonal influenza vs other patient groups) reported no or negative non-significant associations.

CONCLUSIONS/SIGNIFICANCE

We found that SES was significantly associated with pandemic influenza outcomes with people of lower SES having the highest disease burden in both 1918 and 2009. To prepare for future pandemics, we must consider social vulnerability. The protocol for this study has been registered in PROSPERO (ref. no 87922) and has been published Mamelund et al. (2019).

The 1918 influenza pandemic did not accelerate tuberculosis mortality decline in early-20th century Newfoundland: Investigating historical and social explanations

OBJECTIVES

The selective mortality hypothesis of tuberculosis after the 1918 influenza pandemic, laid out by Noymer and colleagues, suggests that acute exposure or pre-existing infection with tuberculosis (TB) increased the probability of pneumonia and influenza (P&I) mortality during the 1918 influenza pandemic, leading to a hastened decline of TB mortality in post-pandemic years. This study describes cultural determinants of the post-pandemic TB mortality patterns in Newfoundland and evaluates whether there is support for this observation.

MATERIALS AND METHODS

Death records and historical documents from the Provincial Archives of Newfoundland and Labrador were used to calculate age-standardized island-wide and sex-based TB mortality, as well as region-level TB mortality, for 1900-1939. The Joinpoint Regression Program (version 4.8.0.1) was used to estimate statistically significant changes in mortality rates.

RESULTS

Island-wide, females had consistently higher TB mortality for the duration of the study period and a significant shift to lower TB mortality beginning in 1928. There was no similar predicted significant decline for males. On the regional level, no models predicted a significant decline after the 1918 influenza pandemic, except for the West, where significant decline was predicted in the late-1930s.

DISCUSSION

Although there was no significant decline in TB mortality observed immediately post-pandemic, as has been shown for other Western nations, the female post-pandemic pattern suggests a decline much later. The general lack of significant decrease in TB mortality rate is likely due to Newfoundland's poor nutrition and lack of centralized healthcare rather than a biological interaction between P&I and TB.

Race and 1918 Influenza Pandemic in the United States: A Review of the Literature

During epidemics, the poorest part of the population usually suffers the most. Alfred Crosby noted that the norm changed during the 1918 influenza pandemic in the US: The black population (which were expected to have higher influenza morbidity and mortality) had lower morbidity and mortality than the white population during the autumn of 1918. Crosby's explanation for this was that black people were more exposed to a mild spring/summer wave of influenza earlier that same year. In this paper, we review the literature from the pandemic of 1918 to better understand the crossover in the role of race on mortality. The literature has used insurance, military, survey, and routine notification data. Results show that the black population had lower morbidity, and during September, October, and November, lower mortality but higher case fatality than the white population. The results also show that the black population had lower influenza morbidity prior to 1918. The reasons for lower morbidity among the black population both at baseline and during the herald and later waves in 1918 remain unclear. Results may imply that black people had a lower risk of developing the disease given exposure, but when they did get sick, they had a higher risk of dying.