Associations between Minority Health Social Vulnerability Index Scores, Rurality, and Histoplasmosis Incidence, 8 US States

Abstract

To explore associations between histoplasmosis and race and ethnicity, socioeconomic status, and rurality, we conducted an in-depth analysis of social determinants of health and histoplasmosis in 8 US states. Using the Minority Health Social Vulnerability Index (MH SVI), we analyzed county-level histoplasmosis incidence (cases/100,000 population) from the 8 states by applying generalized linear mixed hurdle models. We found that histoplasmosis incidence was higher in counties with limited healthcare infrastructure and access as measured by the MH SVI and in more rural counties. Other social determinants of health measured by the MH SVI tool either were not significantly or were inconsistently associated with histoplasmosis incidence. Increased awareness of histoplasmosis, more accessible diagnostic tests, and investment in rural health services could address histoplasmosis-related health disparities.

Keywords: United States; dimorphic fungi; fungi; health equity; healthcare access; healthcare infrastructure; histoplasmosis; rural health; social vulnerability index.

Figure 1

County-level histoplasmosis incidence (cases/100,000 persons) in 8 US states for which data were available, 2011–2014 and 2019–2020. Inset map indicates the 8 states.

Figure 2

Percentage of counties in each state with >1 reported case of histoplasmosis in 8 US states for which data were available, 2011–2014 and 2019–2020.

Figure 3

Distribution of county-level incidence (ordered from highest mean incidence to lowest mean incidence) in 8 US states for which data were available, 2011–2014 and 2019–2020. Boxplots show the medians (vertical black lines), interquartile ranges (box left and right ends), and range +1.5 × interquartile range (error bars); the points show the raw data.

Figure 4

Associations between rurality and histoplasmosis incidence for counties reporting >1 case in 8 US states for which data were available, 2011–2014 and 2019–2020. Incidence rate ratios for conditional component (green) and odds ratios for the probability of observing >1 case in the zero-inflated component (orange) are shown 95% CIs (error bars) by county rural classification; reference group is large metropolitan counties.

Figure 5

Associations between rurality and histoplasmosis incidence for counties reporting >1 case in 8 US states for which data were available, 2011–2014 and 2019–2020. For counties with >1 case of histoplasmosis, bivariate map shows county incidence (split into low-, mid-, and high-incidence tertiles) versus rurality (micropolitan and noncore, medium and small metropolitan, and large metropolitan counties); colors indicate the combination of incidence-rurality levels for each county. Counties without a case are shown in white. Inset map indicates names of the 8 states.

Figure 6

Model effect estimates for association of histoplasmosis incidence with MH SVI themes in 8 US states for which data were available, 2011–2014 and 2019–2020. MH SVI theme scores are interpreted as percentiles; higher scores represent more vulnerable counties. Left column shows incidence rate ratios for the conditional component; right column shows odds ratios for the probability of observing a case in the zero-inflated component. Error bars indicate 95% CIs. Shapes indicate the tertile (mid-tertile or high-tertile, with low-tertile as the reference level), and color indicates the model (model with all counties vs. those stratified by rural classification). Statistically significant effects are indicated by a black outline and increased opacity of points. MH SVI, Minority Health Social Vulnerability Index.