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Over the past several days, wildfires have ravaged vast parts of Los Angeles, leaving behind scenes of devastation. The widespread damage to landscapes, homes, businesses, and infrastructure is only part of the story. Fires of this magnitude carry far-reaching effects on human health, many of which remain less understood but no less concerning.
While the immediate harm of fires—burns, smoke inhalation, and loss of life—is evident, the long-term consequences of wildfire exposure are equally alarming. With a current death toll of at least 24 people in Los Angeles, the focus is now turning to the often-overlooked health risks that come from fires of this scale: infections.
Immune System Disruption
The effects of fire on the human body extend beyond the physical trauma of burns or inhaling toxic smoke. Both burns and smoke inhalation are known to induce significant changes in the immune system, rendering those affected more vulnerable to infections. When severe burns occur, certain immune responses become overstimulated, leading to hyper-inflammation that can result in sepsis or organ failure. Simultaneously, other immune functions are suppressed, impairing the body’s ability to fight infections, making individuals prone to diseases such as pneumonia and respiratory infections for years after the injury.
Wildfire smoke, a hazardous mixture of particulate matter, volatile organic compounds, ozone, and toxic gases, further exacerbates the situation. Studies show that smoke inhalation can increase inflammation in the respiratory system, heightening susceptibility to respiratory infections and asthma. After Australia’s devastating 2019–20 bushfires, a study found a higher risk of COVID-19 infections in areas of New South Wales where fires had occurred weeks earlier, suggesting that the effects of smoke exposure could linger long after the flames subside.
While research on these long-term immune responses is ongoing, it is clear that the impact of wildfire exposure on immune health can be severe and prolonged.
Microbes in the Air
Wildfires also facilitate the movement of microbes—bacteria, fungi, and other pathogens—into populated areas. When fires burn through forests and natural areas, they disturb the soil, releasing microbes that are normally confined to these environments. These microbes travel with smoke and can be carried for hundreds of miles. Some species remain viable in the air for extended periods, landing in urban areas and potentially causing infections.
Studies from Utah have shown that wildfire smoke can carry live microbial species long distances, some of which are capable of infecting humans. In particular, soil-borne fungi such as Coccidioides immitis and Coccidioides posadasii are of concern. These fungi, which thrive in dry soils, can cause valley fever—a lung infection that mimics flu symptoms and is common in the arid regions of the western United States. Research has shown elevated rates of valley fever infections in wildland firefighters and an increased risk of hospital admissions for valley fever in populations exposed to wildfire smoke.
However, findings have been mixed. While some studies report a clear connection between wildfire smoke exposure and higher infection rates, others show limited evidence of increased infections. These contrasting results highlight the need for further investigation to understand the full scope of wildfire smoke’s infectious potential.
Preventive Measures and Public Health Response
As the wildfire season intensifies, the risk of infection among affected populations grows. While more research is needed to fully understand the pathways through which wildfires promote infection, public health responses should include infection prevention strategies, such as the use of effective masks and respiratory protection for those at risk. Moreover, it is essential to establish surveillance systems that can detect and manage potential outbreaks before they spread.
The overcrowding often seen in emergency shelters following major disasters like wildfires further compounds the risk of infections spreading. The risk is not only due to smoke exposure but also due to the close quarters in which displaced people are forced to live.
As the world watches, it is clear that the aftermath of wildfires presents significant public health challenges that extend far beyond the immediate trauma. By better understanding the long-term effects on the immune system and the spread of infectious agents, we can prepare for the ongoing health threats posed by these increasingly frequent disasters.
