Surveillance for Coccidioidomycosis, Histoplasmosis, and Blastomycosis During the COVID-19 Pandemic — United States, 2019–2021

Discussion

Coccidioidomycosis, histoplasmosis, and blastomycosis caused substantial illness nationwide during 2019–2021. The predominance among males, older adults, and AI/AN persons aligns with previous data and historical trends (5). Yearly case count fluctuations during 2019–2021, changes in seasonality, and increase in the blastomycosis CFR in 2021 were atypical and are potentially related to the COVID-19 pandemic, which might have affected acquisition, diagnosis, management, and reporting of these three fungal diseases. Seasonality is not typically observed nationally for these diseases, and the low percentage of cases observed during spring 2020 compared with spring 2019 and spring 2021 might be related to reduced health care–seeking behavior associated with concerns about potential COVID-19 transmission in health care settings. This delay or avoidance of medical care, which was prevalent in the early months of the pandemic (6), likely exacerbated misdiagnosis and diagnostic delays. Fewer reported coccidioidomycosis and histoplasmosis cases in 2020 compared with both 2019 and 2021 might also reflect changes in health care–seeking behavior, preventative measures for respiratory diseases such as mask-wearing, reduced travel to areas endemic for these fungal diseases, lower clinical suspicion of fungal infections given the focus on COVID-19, or underreporting by overwhelmed public health agencies (5). Until 2020, coccidioidomycosis cases had been consistently increasing each year since 2014.^†† Compared with 2019, histoplasmosis case counts declined by 10% in 2020, but subsequently increased 44% in 2021 compared with 2020 (5). COVID-19 transmission concerns that prompted persons to spend more time outdoors in 2020 and 2021 than in 2019^§§ might have increased exposure to pathogenic fungi. Further research is needed to understand the marked rise in reported histoplasmosis cases from 2020 to 2021.

Although in-hospital blastomycosis mortality has increased in recent years (9), the 2021 blastomycosis CFR (17%) was unusually high, particularly given the stable hospitalization rates during the reporting period, which was consistent with prepandemic rates; blastomycosis CFR generally ranges from 8%–10% (5,9). Diagnosis of blastomycosis is challenging because symptoms are nonspecific and the availability of laboratory tests is limited; diagnostic delays exacerbated by the pandemic might have impeded prompt management of blastomycosis or associated comorbidities, which could have led to more severe or disseminated disease during the pandemic. Some health departments noted that COVID-19 prompted better access to death reports and additional scrutiny of contributing causes of death, which might have influenced the observed CFR (10).

The racial and ethnic disparities observed in 2020–2021 generally align with those reported in 2019, with higher incidence of all three diseases among AI/AN persons as well as higher incidence of coccidioidomycosis among Hispanic persons and higher incidence of blastomycosis among A/NHOPI persons compared with incidence in White populations (5). Similar to coccidioidomycosis and blastomycosis, histoplasmosis incidence was also higher among AI/AN than White persons, which differed from 2019, when incidence was similar across racial and ethnic groups (5). How these racial and ethnic disparities might be affected by geographic, biologic, or sociodemographic differences is not clear. More complete and detailed race and ethnicity data are needed to better understand how these factors influence disease and to guide actionable public health responses.

Limitations

The findings in this report are subject to at least three limitations. First, because of longstanding diagnostic challenges, case counts underestimate the actual number of coccidioidomycosis, histoplasmosis, and blastomycosis cases, and data are limited to the subset of states where each disease is reportable (4). Second, data related to potential exposures, underlying conditions, laboratory testing, clinical course, and treatment were not available, hindering the ability to distinguish the potential effects of the COVID-19 pandemic from other influences, including weather patterns, awareness, or testing and reporting practices. Data were incomplete for race and ethnicity, event month, hospitalization, and death, and the lack of event date standardization could lead to misclassification of monthly case counts. Finally, only aggregate-level data were available for histoplasmosis and blastomycosis, which precluded bivariate analyses.

Implications for Public Health Practice

Increased awareness is needed to improve prompt diagnosis and treatment of coccidioidomycosis, histoplasmosis, and blastomycosis, particularly during periods of increased incidence of other respiratory diseases. To reduce misdiagnosis of these three fungal infections, standardized diagnostic guidance and informational resources for pan-respiratory testing, including fungal diseases, are needed and could be incorporated into broader respiratory disease awareness and preparedness efforts. Education to help clinicians distinguish fungal pneumonia from other respiratory infections might improve accurate diagnosis. Enhanced and expanded surveillance can also improve understanding of risk factors and epidemiologic trends to help guide efforts to raise awareness and improve diagnosis, management, and patient outcomes.