August 25, 2025 – An unexpected culprit has been found to be fueling the severity of one of the most dangerous fungal infections in humans: a virus living inside the fungus, according to Hebrew University of Jerusalem (HU) researchers. 

The Aspergillus fumigatus fungus is already notorious in medical circles. Responsible for the majority of invasive fungal infections in humans, it is especially lethal for people with weakened immune systems. Despite decades of research, mortality rates from infections remain alarmingly high, approaching 50%. 

According to research published in Nature Microbiology, Aspergillus fumigatus significantly boosts the fungus’s ability to survive stress and cause severe infections in mammals. Removing the virus made the fungus weaker and less virulent, while antiviral treatments improved survival outcomes. This finding reveals a hidden factor driving the deadliness of fungal infections and opens the door to potential new treatments that target the virus rather than the fungus itself. 

The research was led by Dr. Marina Campos Rocha, Dr. Vanda Lerer, Ph.D., and student John Adeoye under the supervision of Dr. Neta Shlezinger, all from the Hebrew University Koret School of Veterinary Medicine. Their work showed that Aspergillus fumigatus fungus gives the virus a powerful survival advantage—making it tougher, more resilient, and ultimately, more dangerous to human health. 

“These viruses are like molecular backseat drivers,” says Dr. Shlezinger. “They don’t cause disease on their own, but they influence how aggressively the fungus behaves once it’s inside the body.” 

Virus-Cured Fungi Lose Their Edge 

To test the virus’s impact, the researchers removed it from fungal strains and compared their behavior to that of their virus-infected counterparts. The difference was striking. The virus-free fungi lost their ability to reproduce effectively, showed weaker defenses like reduced melanin production, and became significantly less dangerous when introduced into mammalian lungs. 

The findings suggest that these so-called “mycoviruses” may play a quiet but critical role in the development and progression of fungal diseases in humans, a role that has largely gone unnoticed in the medical mycology field. 

When antiviral treatments were used to suppress the virus during infection, survival outcomes improved in the mammalian model. This could open a whole new avenue for new treatment—not just targeting the fungus itself, but the virus helping it thrive. 

This discovery also indicates a rethinking of how fungal infections are treated. By targeting the virus within the fungus, researchers may one day weaken the pathogen enough for the immune system—or existing antifungal drugs—to fight back more effectively. 

The research paper titled  “Aspergillus fumigatus dsRNA virus promotes fungal fitness and pathogenicity in the mammalian host” is now available in  Nature Microbiology  and can be accessed here.

Researchers:

Marina Campos Rocha¹, Vanda Lerer¹, John Adeoye¹, Hilla Hayby¹, Maria Laura Fabre², Amelia E. Barber², Neta Shlezinger¹

Institutions:

1. Koret School of Veterinary Medicine, Faculty of Agriculture, The Hebrew University
2. Institute of Microbiology, Friedrich Schiller University