It's a plotline straight out of science fiction: humans infected by plant pathogens. But experts confirm it is possible, though incredibly rare.
Dr. Soma Dutta, a physician and medical microbiologist at Apollo Multispeciality Hospitals in Kolkata, India, explains that it is extremely rare for a pathogen to jump from a plant to a human because our biological architectures are fundamentally different. Plant pathogens have evolved to breach thick, rigid walls of cellulose, while human cells are protected by lipid membranes. Additionally, the higher average temperature of the human body acts as a furnace, denaturing their proteins.
However, there are exceptions. In 2023, Dutta and colleague Ujjwayini Ray published a case report about a 61-year-old plant mycologist who developed a persistent cough and sore throat. Doctors found a pus-filled abscess beside his windpipe containing spores from Chondrostereum purpureum, a fungus that causes silver leaf disease in plants. The patient recovered after a course of antifungal tablets.
Silver leaf fungus (Chondrostereum purpureum), which typically harms plants, infected a man in India. (Credit: Adrian Crook/Getty Images)
In rare situations, plant pathogens typically affect those with weakened immune systems, which can be fatal. For example, the bacterium Pantoea agglomerans causes disease in food crops like rice and maize, and if it enters the human bloodstream, it can be deadly. Burkholderia causes rot in onions and rice and has infected cystic fibrosis patients, causing pneumonia and blood poisoning.
As for plant viruses, they are generally believed not to pose a risk to humans. However, researchers found RNA of pepper mild mottle virus in human stool samples, correlated with fever and itchy skin. Tobacco mosaic virus has been detected in cigarette brands and in the saliva of smokers, raising tentative questions about its role in smoking-related cancers.
Plant pathogens have evolved to breach the thick, rigid walls of cellulose or hemicellulose inside plants cells (right). Meanwhile, human cells (left) are protected by lipid membranes, which plant pathogens generally don't have the tools to break through. (Credit: Photo By Encyclopaedia Britannica/UIG Via Getty Images)
Dr. Dutta warns that climate change may be eroding the most significant barrier: temperature. As global temperatures rise, plant pathogens may adapt to warmer conditions, equipping them to survive in human bodies. The final message: 'Rare' does not mean 'impossible.'