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California: Occupational Infections and Workers' Compensation: Proving Industrial Exposure in Valley Fever Cases

January 27, 2022 (10 min read)

With the novel COVID-19 pandemic still looming so large in our collective vision, it is sometimes easy to forget that infections have long been part of the landscape of our workers’ compensation system. An infection may be bacterial, like tuberculosis; viral, like some forms of pneumonia; or it may be fungal, like coccidiomycosis (aka valley fever). Of course, whether any infection is covered by workers’ compensation liability turns on whether it arose out of and occurred in the course of employment. Two recent Appeals Board panel decisions revisit the question of whether or not an employer has workers’ compensation liability for the valley fever infections sustained by their respective employees. The cases are Shuere v. State of California, Department of Youth Authority (Shuere) (ADJ11413863, December 20, 2021) and Dieball v. State of California, Department of Corrections—Men’s Colony (Dieball) (ADJ11330624, January 13, 2022). These two panel opinions serve as practical reminders of the elements required to establish industrial causation when the claimed industrial injury is an infection.

The Facts

The underlying facts in Shuere and Diebal are quite similar. Both Shuere and Diebell became infected with valley fever and sustained injury to their respiratory systems. Valley fever is an infection caused by a fungus, coccidioides, which is found in the soil in certain parts of California. When soil is disturbed the fungal spores can become airborne, allowing them to be inhaled. Shuere, a vocational instructor employed by the California Youth Authority, claimed that his work location exposed him to the fungus because the facility’s layout required him to spend a great deal of time outside to travel from the parking lot to his actual work premises. Shuere’s employer disputed the claim, arguing that Shuere could have become infected elsewhere because his work site did not place him at a greater risk of exposure to valley fever than the general public. Shuere was evaluated by a Panel Qualified Medical Evaluator (PQME). The PQME acknowledged that the fungus that causes valley fever lives in soil and exposure to it typically occurs after the soil has been disturbed. He also admitted that it would be extremely difficult if not impossible to prove that soil from a particular location harbored the fungus that caused the infection. Thus, to assess the cause of Shuere’s valley fever, the PQME explained that it was necessary to compare the proportion of time Shuere was exposed to dirt outdoors at work with the proportion of time he was exposed outside of work. Based on that proportional comparison, the PQME concluded that it was medically probable that Shuere was exposed to the fungus at work. The WCJ accepted the PQME’s opinion as substantial medical evidence and found that Shuere sustained an industrial injury in the form of valley fever.

Dieball, a correctional officer, claimed that his one to two-hour daily shifts patrolling the prison yard where he worked exposed him to open areas of dirt, one of which was under construction. Defendant disputed the claim, contending that it was just as likely that Dieball became infected at his own home or some other location outside of the work site. Dieball was evaluated by a physician appointed by the WCJ pursuant to Labor Code section 5701. That physician, Dr. Tirmizi, explained that a construction site is not the only venue in which a coccidioides spore can become airborne and inhaled—rather, inhalation of a spore can occur simply if a person walks in an area with dirt where wind gusts can aerosolize the spores. Dr. Tirmizi considered Dieball’s exposure to dirt at work while patrolling outside in comparison with his exposure outside of work. Dr. Tirmizi characterized any home exposure as “low risk,” noting that a home setting is not conducive to wind gusts that aerosolize spores to be inhaled. In contrast, Dr. Tirmizi found the environment around the prison to present a more significant risk for inhalation of spores since a prison complex typically is clear of greenery and foliage, which can cause soil to become dry and aerosolized. The WCJ found Dr. Tirmizi’s opinions substantial medical evidence that Dieball’s valley fever infection arose out of and occurred in the course of his employment.

The Issues on Reconsideration

The defendant in Shuere and the defendant in Dieball each sought reconsideration of the findings in their respective cases. In Shuere, defendant argued that the opinions of the PQME did not constitute substantial medical evidence of industrial injury because his analysis of the facts was flawed. Defendant also argued that Shuere’s work site did not place him at a greater risk than the general public for contracting valley fever. In Dieball, defendant argued that valley fever is a nonoccupational infection caused by spores that are present in the environment of Dieball’s home as well as his work site. Defendant also challenged Dr. Timrizi’s opinions as lacking substantial medical evidence.

The Panels’ Analyses

The Appeals Board panels’ opinions in Shuere and Dieball are especially instructive because of their step-by-step review of the requisite elements to support a finding of injury arising out of and occurring in the course of employment (AOE/COE). Foremost, they acknowledge that the employee has the burden of proving reasonable probability of industrial causation, but that does not require proof of causation to a scientific certainty; rather, it is sufficient if work is a contributing cause of the injury. (McAllister v. Workmen’s Comp. Appeals Bd. (1968) 69 Cal. 2d 408 [33 Cal. Comp. Cases 660; South Coast Framing, Inc. v. Workers’ Comp. Appeals Bd. (2015) 61 Cal. 4th 291, 298 [80 Cal. Comp. Cases 489].)

Next, each opinion points to the well-established two-part test for determining whether an injury is AOE/COE. (La Tourette v. Workers’ Comp. Appeals Bd. (1998) 17 Cal. 4th 644 [63 Cal. Comp. Cases 253].) Part one requires the injury to occur in the course of employment, which refers to the time, place and circumstances under which an injury occurs. (La Tourette, supra, 63 Cal. Comp. Cases 256). An employee acts within the course of employment when they do those reasonable things that the contract of employment expressly or impliedly permits to be done. Part two requires the injury to arise out of employment, which means that the injury and employment must be linked in some causal manner. In other words, the injury must occur by reason of a condition or incident of employment (Employers Mutual Liability Ins. Co. of Wisconsin v. Industrial Acc. Com. (1953) 41 Cal. 2d 676 [18 Cal. Comp. Cases 286]; Maher v. Workers’ Comp. Appeals Bd. (1983) 33 Cal. 3d 729 [48 Cal. Comp. Cases 326, 329].)

In many instances, the issue of whether an injury is industrial requires expert medical opinion. To constitute substantial medical evidence, the expert’s opinion must be framed in terms of reasonable medical probability, must be based on an accurate history and examination, and must set forth a rationale to support the expert conclusions reached. (E.L. Yeager v. Workers’ Comp. Appeals Bd. (Gatten) (2006) 145 Cal. App. 4th 922, 928 [71 Cal. Comp. Cases 1687].) Any medical opinion that falls short of these requirements cannot rise to the level of substantial evidence. (Zemke v. Workmen’s Comp. Appeals Bd. (1968) 68 Cal. 2d 794 [33 Cal. Comp. Cases 358].)

When an injury is claimed to have been caused by an infectious process, it may not be possible to answer the questions when and where the employee contracted the disease with any certainty. How can the employee prove that the infection arose out of and occurred in the course of employment? The Shuere and Dieball opinions give us the answer. The employee can establish industrial causation by demonstrating that it is more probable that they acquired the disease at work, or that the employment subjected the employee to a special risk of exposure in excess of that of the general public. (Bethlehem Steel Co. v. Industrial Acci. Com. (1943) 21 Cal. 2d 742 [8 Cal. Comp. Cases 61].) Shuere and Dieball specifically discuss two cases that found industrially caused infection based on medical opinion that it was more likely than not that the employee contracted the virus at work. The first case is City of Turlock v. Workers’ Comp. Appeals Bd. (2007) 72 Cal. Comp. Cases 931, 934 (writ den.) In City of Turlock, a sewage employee’s Hepatitis C infection was found industrial based on medical opinion that it was more probable than not that work was the source of the employee’s infection. The second case is Pacific Employers Ins. Co. v. Industrial Acci. Com. (1942) 19 Cal. 2d 622 [7 Cal. Comp. Cases 71], wherein the Supreme Court considered whether a traveling salesman’s valley fever infection arose out of and occurred in the course of his employment. In affirming the finding of industrial injury, the Court explained that it is the medical expert’s job to assess whether it is medically probable that transmission of the infection occurred at work. The Court went on to emphasize that the opinions of physicians are entitled to consideration because it is part of their vocation to observe diseases and how they are spread and draw conclusions from them.

The majority on the Shuere panel affirmed the WCJ’s finding that applicant met his burden of proof that his valley fever infection arose out of and occurred in the course of his employment based on the substantial medical reporting of the PQME, which was unrebutted. The PQME opined that in the case of valley fever it is not possible to pinpoint the exact location of exposure by taking samples of dirt from different possible sources. Therefore, a proportional assessment regarding potential exposure is the best method to use to identify the most likely source. Taking into consideration the amount of time Shuere spent outdoors at work exposed to dirt that could have harbored coccidioides in comparison to the amount of time Shuere spent outdoors exposed in all other locations, the PQME concluded that it was more probable than not that Shuere contracted valley fever through his work exposure. Because Shuere satisfied his burden of proving injury AOE/COE on the “more probable than not” theory of exposure, the majority agreed that it was not necessary to develop the record on an alternative theory of causation.

It is important to note that one Commissioner dissented. The dissenting Commissioner would have returned the case to the trial level for further development of the record as to whether or not Shuere’s employment placed him at a greater risk of exposure to valley fever than the general public. The dissent contends that the requisite causal link between Shuere’s infection and work can only be shown by evidence that the work site exposed Shuere to a greater risk of exposure than that of the general public.

The Dieball panel affirmed the WCJ’s finding of injury AOE/COE after concluding that Dieball met his burden of proving injury AOE/COE based on the medical reporting of Dr. Tirmizi. In a unanimous opinion, the panel explains why it found Dr. Tirmizi’s opinion that it was more likely than not that Dieball’s work site was the source of exposure to valley fever to be substantial evidence. Specifically, Dr. Tirmizi discussed the typical environment around a prison as being devoid of greenery and foliage, causing soil to become dry and more likely to become aerosolized by a gust of wind. In contrast, Dr. Tirmizi described a home environment as one that would not typically allow for aerosolization of dirt or spores. Dr. Tirmizi found it significant that Dieball’s job duties required him to spend up to two hours a day outside on patrol near areas with dirt. These factors caused Dr. Tirmizi to conclude that Dieball’s work as a yard supervisor exposed him to a greater risk of exposure to aerosolized coccidioides than the general public, making it more probable that exposure to the infection occurred at work.


We live in a time of impressive scientific advancements. Nonetheless, it is highly unlikely that disease and infection will not become relics of the past anytime soon. What is a certainty is that infections will continue to occur and some infections will be claimed to be of industrial origin. An industrial infection claim may be more complex than many other types of injuries, but it is not impossible for the injured worker to demonstrate that the infection arose out of and occurred in the course of employment. The Shuere and Dieball opinions are two excellent examples of the factors required to make a successful showing of injury AOE/COE.

Reminder: Panel decisions are not binding precedent.

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