Title: Changing Geographic Distributions of Coccidioides spp. in the United States: A Narrative Review of Climate Change Implications
Authors: Jackie Chung OMS4; Zachary Parker OMS3; Beeta Shasti OMS3; Kimberly Taylor, PhD
Introduction
Coccidiodes spp. Is a respiratory disease causing fungus historically considered endemic to the southwestern U.S. but is increasingly recognized outside of this classic endemic zone. We analyze alterations in the United States prevalence of coccidiomycosis in geographic regions historically considered to not be endemic for the Coccidioides spp. pathogen with an evaluation of changing climate patterns within those areas.
Methods
The databases MEDLINE, Google Scholar, PubMed, and CINAHL were searched for English-language sources with combinations of the following keywords: climate change, Coccidioides, distribution, and United States with relevant synonyms. Preference was given within the inclusion criteria to sources published in the past 20 years. The bibliographies of the retrieved publications were also searched. Exclusion criteria included sources relative to areas outside the continental United States.
Results
Although Coccidioides species have classically been recognized as endemic to the southwestern United States, isolates have been found far outside this area and recent investigations have demonstrated a growing endemic zone. Ecological and outbreak data supports the conclusion that these findings result from a growing endemic range that is estimated to be as far east as Texas and as far north as Washington State. Investigations point to climate change as the underlying cause primarily via regional climate changes and large dust storms.
Discussion
The geographic distribution of Coccidioides fungus is known to be larger than classically recognized or potentially considered in the formation of diagnostic differentials in the clinical setting. Timely diagnosis, appropriate treatment approaches, and accurate reporting for public health surveillance rely on a recognition of endemic range expansion. Physician education (via medical school curriculums and continuing education offerings), interprofessional team-based approach, and enhancement of surveillance in locations in potentially geographically novel areas are appropriate measures in improving the identification of coccidiomycosis cases.
Case studies from local outbreaks and natural disasters support adding coccidioidomycosis to a list of other infectious diseases (e.g., those that are vector borne) whose endemic areas are spreading due to climate change. Recognition of underlying climate change related mechanisms should also prompt steps to reduce environmental spread where mitigation is possible. Current climate model predictions support an expected increase in Coccidioides spp. infection; further research is recommended to clearly define the relationship between climate change and Coccidioides spp. geographic expansion.
Nice presentation. My question is whether the disease distribution and endemic can be used interchangeably. For example, if a disease is found only occasionally in an area, is that still considered “endemic”? What is the criteria to determine if a disease is “endemic”?
Thank you for pointing this out.
We should be more careful in our discussion to specify geographic range.
Endemic is defined as the constant presence and/or usual prevalence of a disease or infectious agent in a population within a geographic area (CDC).
So in several of the places including WA, where the disease is not regularly found it would be more appropriate to refer to it as part of the geographic range rather than endemic zone.
There is an assumption that the disease is underreported in many areas that don’t regularly test for it. So the actual endemic range may evolve as more providers are aware of the disease as well. I did not find quantitative criteria to define endemic.
Thank you for your presentation, Student Dr. Parker. I have been assigned as a judge for your project. know you said this can lead to “indolent pulmonary infections in most,” , but can you more specifically describe the age-related distributions of this condition and overall prevalence and/or incidence? Thanks again.
No problem. Per CDC data, incidence in 2019 was about 18,000 with highest rates in people of 60 and older.
The disease is believed to be underreported. It is not a reportable disease in all states and even in highly endemic areas such as Phoenix and Tucson, there are low testing rates.
When clinical disease is present it most often presents similar to a community acquired pneumonia, but in immunocompromised people can disseminate to other body systems. In the immunocompetent, an infection may be cleared before that person presents for testing
OK thank you, Student Dr. Parker!
Thanks for this presentation, I am also one of your judges. I’m wondering if the spread of Coccidioides spp. has been associated increases in the prevalence or severity of chronic pulmonary conditions, such as asthma or COPD. Thanks!
Interesting question. I don’t believe our team came across any investigational data looking at this specifically.
I can say that Coccidioidomycosis cases have generally increased since 1998 (with some spikes following natural disasters) per CDC.
While according to the American Lung Association, rates of chronic bronchitis have decreased over the past 2 decades; emphysema for men has also decreased while emphysema in women has slightly increased.
This is just big picture, but I agree that it would be very interesting to look at populations highly affected by Coccidioides and chronic pulmonary conditions