Smoke from the growing number of annual wildfires across the western United States and Australia has led to lengthy periods of unhealthy and hazardous air quality for millions of people living in these regions. In a Perspective, Leda Kobziar and George Thompson III highlight a little-known and poorly understood threat potentially lurking in the plumes - infectious microbes. According to Kobziar and Thompson, wildfire smoke contains living microbes - bacteria and fungi known to affect human health - aerosolized from burning materials such as soils, detritus and wild woods and transported in smoke plumes. However, while the pulmonary and cardiovascular consequences of smoke exposure are well known and recognized, the potential for wildfire smoke to be a source of infection has been overlooked and remains unaddressed in public health and wildfire science. To date, very little research has been done to determine whether the transport of smoke-borne microbes poses a health risk, in addition to the risk known from particulate inhalation, despite compelling evidence that shows increasing rates of certain fungal infections in areas with increased levels of wildfire smoke. Kobziar and Thompson argue that the potential for a wildfire's microbial content to affect humans who breathe in smoke, particularly from large fires and over long periods, is appreciable. Thus, atmospheric and public health sciences must expand their focus to include the potential impact of smoke's microbial cargo on human populations - a goal that is especially relevant where smokey skies are more likely to become a seasonal norm rather than a rare event, write the authors.