A recent study presented at the American Society for Microbiology's annual meeting (ASM Microbe 2025) in Los Angeles has uncovered a surprising link between airborne fungal spores and short-term spikes in flu and COVID-19 cases. The research, conducted by scientists from Lynn University in Florida, suggests that monitoring outdoor levels of fungal spores could provide an early warning system for potential outbreaks.Not Just Human Contact: A New Environmental PlayerTraditionally, respiratory illnesses like flu and COVID-19 have been associated mainly with human-to-human transmission. But this new research introduces an environmental twist: airborne fungal spores — microscopic particles released by fungi into the air — may play a significant role in triggering infection surges.Researchers found that when levels of fungal spores in the outdoor air increased, there was a corresponding rise in COVID-19 and flu infections in the days that followed. What’s more, the relationship was strong enough that statistical and machine learning models could predict these spikes with a high degree of accuracy.Interestingly, the same predictive relationship did not hold true for pollen, another common airborne particle. This indicates that fungal spores may have a more specific and direct impact on respiratory health than previously assumed.Data from the Tropics: What Puerto Rico RevealedThe research team focused their study on two major health regions in Puerto Rico — San Juan and Caguas — collecting data from 2022 to 2024. They tracked the daily incidence of flu and COVID-19 diagnoses alongside environmental measurements of fungal spores and pollen.Using both traditional statistical analysis and machine learning models, they examined whether spikes in fungal spore concentrations could predict increases in infections within the same week or the following week — a concept known as a lag effect. The results were striking: in many instances, elevated levels of fungal spores were followed by noticeable jumps in flu and COVID-19 cases.A Tool for Better Public Health Planning“This research gives us a new lens through which to view respiratory virus outbreaks,” said Felix E. Rivera-Mariani, Associate Professor of Biochemistry at Lynn University and lead researcher on the study. “By monitoring environmental data like fungal spores, we can potentially issue earlier warnings and protect high-risk communities.”Rivera-Mariani emphasized that this approach could be especially useful in the fall — a season that already sees increased viral transmission — when fungal spore levels are often high due to decaying plant matter and damp conditions.He added that this discovery highlights a broader message: “Environmental triggers, not just interpersonal contact, may influence how and when people get sick. That insight could help shape future public health responses and inform protective guidelines, particularly in regions with high fungal activity.”Who Stands to Benefit?The findings may be especially valuable for protecting vulnerable populations such as the elderly, individuals with asthma, or people with allergic rhinitis. These groups are not only more prone to respiratory infections but may also be more sensitive to environmental irritants like fungal spores.By incorporating airborne fungal spore monitoring into existing public health surveillance systems, authorities could issue timely alerts and recommendations — including when to wear masks, avoid outdoor exposure, or ramp up testing.While more research is needed to fully understand the biological mechanism behind this connection, the evidence presented marks a promising step toward using environmental data to predict — and possibly prevent — future outbreaks.