COVID-19 and Wildland Firefighters

Posted on by Kathleen Navarro, PhD, MPH; Daniel Hardt, MS, CIH; and Kathleen Clark PhD, MS, RRT

Wildfires do not stop during a pandemic. The 2020 fire season saw the first-ever single wildfire to burn over 1 million acres, with 44 days at the highest fire preparedness level (and 30 days higher than the 5-year average) when fire personnel and resources are extremely scarce. Circumstances surrounding wildfire incidents can put wildland firefighters at increased risk for the transmission of infectious diseases including COVID-19, due to the fact that firefighters:

  • Work and live in close conditions (riding in shared vehicles, performing fire suppression tasks in close contact, and eating and sleeping in congregate housing).
  • Have limited access to hygiene supplies due to the remote nature of fire camp locations.
  • Need to respond to incidents all over the country on short notice, resulting in frequent travel and possible close contact with the public and other fire resources and personnel.

Additionally, occupational factors that increase stress on the body such as arduous work, long work shifts, and environmental exposures (including wildfire smoke) may contribute to increased susceptibility and potentially more severe illness for COVID-19 [1,2].

In the review article Wildland firefighter exposure to smoke and COVID-19: A new risk on the fire line, researchers examined how exposure to wildfire smoke can contribute to an increased likelihood of infection with SARS-CoV-2 (the virus that causes COVID-19) and increased severity of COVID-19.

Considerable evidence indicates an association between exposure to air pollution, including particulate matter (PM) from wildfire smoke, and increased risk for lower respiratory infections. Wildfire smoke exposure has been associated with lower respiratory infections such as acute bronchitis and pneumonia in many epidemiological studies of the public’s exposure to smoke [2-5]. Preliminary studies have found positive associations between SARS-CoV-2 infection and ambient air pollution levels (including PM) [6-8].

Two hypotheses may explain the association between increased cases of COVID-19 and elevated PM exposure. The first hypothesis suggests that SARS-CoV-2 viral clusters stick to PM that can be breathed in, which promotes spread of SARS-CoV-2 through the air by increasing viral transmissibility and viability [9]. Another hypothesis about the association of COVID-19 severity and mortality with elevated exposure to PM involves changes in gene expression (upregulation) of a cellular protein (the angiotensin-converting enzyme two or ACE-2 receptor) that provides the primary entry point for SAR-CoV-2 into specific types of cells [10].

Although these health outcomes have not been studied specifically in wildland firefighters, they can be exposed to elevated concentrations of PM from wildfire smoke. Between 2009 and 2012, the United States Department of Agriculture Forest Service (USFS) reported that 22% of wildfire and 20% of prescribed burn (fires intentionally set for resource benefit) work shifts exceeded the recommended daily occupational exposure limit of PM smaller than 4 microns (PM4, or 0.7 mg/m3) specifically recommended for wildland firefighters [11]. In addition, wildland firefighters, incident management personnel, and fire camp support crews can be exposed to smoke at incident command posts (ICPs) that support thousands of individuals while off the fire line, which can contribute to a higher cumulative work exposure [12,13]. Incident command personnel are often older, not as physically active as wildland firefighter crews, and are more likely to have underlying health conditions that put them at increased risk for severe illness from COVID-19.

Wildfire smoke exposure may also make wildland firefighters more likely to experience severe illness from COVID-19. Chen et al., reported that severe cases of COVID-19 had elevated inflammation biomarkers compared to less severe COVID-19 cases, possibly leading to cytokine release syndrome or “cytokine storm” [14-16]. These biomarkers have historically been shown to be elevated in firefighters during fire suppression activities, so firefighters may be predisposed to suffering from more severe illness if they do get sick with COVID-19 [17,18].

Mitigating exposure to smoke

Mitigating exposures to smoke can be difficult for fire managers and wildland firefighters as smoke is part of the wildfire environment. Mitigation strategies will be dependent on fire behavior, available resources and personnel, and operational objectives. Current mitigations to reduce smoke exposure include:

  • rotating fire personnel in areas of high unavoidable smoke exposure,
  • using air resource advisors to monitor and address smoke issues, and
  • locating ICPs and remote camps in areas with the least smoke exposure practicable [19].

Preventing transmission of SARS-CoV-2

Preventing the spread of COVID-19 may be difficult in the extreme work environments of wildland firefighting personnel. All wildland fire personnel should stay up to date on the basic understanding of COVID-19, how it spreads, symptoms, and what measures they can take to protect themselves and others, including vaccination.

Wildland fire personnel can take the following steps to protect their health, prevent disease, and maintain critical fire operations:

  • Get a COVID-19 vaccine.
  • Adhere to social distancing guidelines.
  • Wear well fitted masks, especially when social distancing is not possible.
  • “Isolate as a unit” or create a “module as one” within their crew to reduce outside exposure to SARS-CoV-2 from the public or other crews [1,20].
  • Screen daily for symptoms of COVID-19 and let your supervisor know if you are experiencing any symptoms to prevent spreading COVID-19 to others.
  • Wash your hands often.

As wildland firefighters continue to do their jobs during this pandemic, steps must be taken to protect these workers from COVID-19 while they put their lives on the line to protect public safety. CDC continues to update the Wildland Firefighter FAQ page to provide wildland fire personnel the most up-to-date information.


Kathleen Navarro, PhD, MPH, is a Senior Service Fellow in the NIOSH Western States Division.

Daniel Hardt, MS, CIH, is an Industrial Hygienist in the NIOSH Western States Division. 

Kathleen Clark PhD, MS, RRT, is a Health Scientist/Research Epidemiologist in the NIOSH Respiratory Health Division.



  1. CDC. [2020]. FAQs for Wildland Firefighters. Centers for Disease Control and Prevention.
  2. Bryant P, Trinder J, Curtis N. Sick and tired: does sleep have a vital role in the immune system? Nature Reviews Immunology. 2004;4:457-467.
  3. Delfino R.J., Brummel S, Wu J, Stern H, Ostro B , Lipsett M, et al [2009].The relationship of respiratory and cardiovascular hospital admissions to the southern California wildfires of 2003. Occup. Environ. Med. 66: 189-197.
  4. Morgan G, Sheppeard V, Khalaj B, Ayyar A, Lincoln D, Jalaludin B, et al. [2010]. Effects of bushfire smoke on daily mortality and hospital admissions in Sydney, Australia. Epidemiology (Cambridge, Mass.), 21: 47-55.
  5. Rappold A.G., Stone S.L., Cascio W.E., Neas L.M., Kilaru V.J., Carraway M.S., et al. [2011]. Peat bog wildfire smoke exposure in rural North Carolina is associated with cardiopulmonary emergency department visits assessed through syndromic surveillance. Environ. Health Perspect., 119:1415-1420.
  6. Zhu Y, Xie J, Huang F, Cao L. [2020]. Association between short-term exposure to air pollution and COVID-19 infection: evidence from China. Sci. Total Environ., 727: 138704.
  7. Accarino G, Lorenzetti S, Aloisio G. [2021]. Assessing correlations between short-term exposure to atmospheric pollutants and COVID-19 spread in all Italian territorial areas. Environ. Pollut., 268:115714.
  8. Wu X, Nethery RC, Sabath MB, Braun D, Dominici F. [2020]. Air pollution and COVID-19 mortality in the United States: strengths and limitations of an ecological regression analysis. Science Advances, 6, eabd4049.
  9. Setti L, Passarini F, De Gennaro G, Barbieri P, Pallavicini A, Ruscio M, et al. [2020]. Searching for SARS-COV-2 on particulate matter: a possible early Indicator of COVID-19 epidemic recurrence. Int. J. Environ. Res. Public Health, 17.
  10. Frontera A, Cianfanelli L, Vlachos K, Landoni G, Cremona G, [2020]. Severe air pollution links to higher mortality in COVID-19 patients: the “double-hit” hypothesis. JoI.
  11. 11 Reinhardt TE, Broyles G. [2019]. Factors affecting smoke and crystalline silica exposure among wildland firefighters. J. Occup. Environ. Hyg., 16: 151-164.
  12. 12.McNamara ML, Semmens EO, Gaskill S, Palmer C, Noonan CW, Ward TJ. [2012]. Base camp personnel exposure to particulate matter during wildland fire suppression activities. J. Occup. Environ. Hyg., 9:149-156.
  13. Navarro KM, Cisneros R, Schweizer D, Chowdhary P, Noth EM, Balmes JR, et al. [2019]. Incident command post exposure to polycyclic aromatic hydrocarbons and particulate matter during a wildfire. J. Occup. Environ. Hyg., 16:735-744.
  14. Chen G, Wu D, Guo W, Cao Y, Huang D, Wang H, et al. [2020]. Clinical and immunological features of severe and moderate coronavirus disease 2019. J. Clin. Invest., 130:2620-2629.
  15. Moore JB, June CH. [2020]. Cytokine release syndrome in severe COVID-19. Science, 368:473.
  16. Pedersen SF, Ho Y-C. [2020]. SARS-CoV-2: a storm is raging. J. Clin. Invest., 130: 2202-2205.
  17. Main LC, Wolkow AP, Tait JL, Della Gatta P, Raines J, Snow R, et al. [2020]. Firefighter’s acute inflammatory response to wildfire suppression. J. Occup. Environ. Med., 62: 145-148.
  18. Adetona AM, Martin WK, Warren SH, Hanley NM, Adetona O, Zhang JJ, et al. [2019]. Urinary mutagenicity and other biomarkers of occupational smoke exposure of wildland firefighters and oxidative stress. Inhal. Toxicol., 31:73-87.
  19. Group NRC. [2020]. Wildland Fire Response Plan COVID-19 Pandemic Northern Rockies Geographic Area. Northern Rockies Coordinating Group National Interagency Fire Center.
  20. MPHAT. [2020]. Interim Guidance for Prevention and Management of COVID-19 during Wildland Fire Operations. Fire Management Board.
Posted on by Kathleen Navarro, PhD, MPH; Daniel Hardt, MS, CIH; and Kathleen Clark PhD, MS, RRT

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Page last reviewed: March 30, 2021
Page last updated: March 30, 2021