Slovenian researchers prove plant viruses remain infective in wastewater

Ljubljana, 21 April - Slovenian researchers are believed to be the first to have proved the existence of abundant plant viruses in waste water that remain infective after conventional wastewater treatment, which means they can infect plants and cause disease when released into the environment.

The latest achievement by researchers of the National Institute of Biology's Department of Biotechnology and Systems Biology has been published in Water Research, a journal of the International Water Association that publishes research on the science and technology of water quality and its management.

The scientists note that presence of plant, animal and human viruses in water is a major risk when wasterwaters are recycled for example for watering plants, a practice applied extensively in many parts of the world.

The release of viruses into rivers may lead to viral transmission if the river water is used for irrigation or if the viruses find a new host such as plants growing near the water.

Considering new findings about the great diversity of viruses in water and their infectivity the Ljubljana-based institute says that effective methods are needed to monitor the presence of pathogenic viruses in water.

The institute has been researching viruses in various water samples for years and is currently focusing on detecting the novel coronavirus in wastewater.

Katarina Bačnik, the lead author of the article published in Water Research, says that plant viruses, that is those that cause disease in plants, are present both when wastewater enters a purifying plant as well as when it is released into a nearby river.

Applying viral concentration technology with the help of purification media made by the Slovenian company BIA Separations and the sequencing of viral nucleic acids, the researchers detected 47 different types of plant viruses, including those not previously reported in Slovenia.

They also proved their infectivity, that is the ability to infect plants both before and after passing through the purifying plant as the plants infected with wastewater showed signs of disease.

Although the study focused on plant viruses, the researchers also detected in wastewater samples the presence of bacteriophages (viruses that infect and replicate within bacteria) and some human viruses that cause gastrointestinal diseases.

Maja Ravnikar, the head of the Department of Biotechnology and Systems Biology at the National Institute of Biology, says that, at the time when virus has become an everyday word, it has become even more obvious how little humanity knows about viruses and how important it is to study them.

The research had been conducted under the leadership of Maja Ravnikar, with young researcher Katarina Bačnik as the lead author and also involving Denis Kutnjak, Ion Gutierrez Aguirre, Nataša Mehle, Anja Pecman and Magda Tušek Žnidarič.

Apart from research project and programme financiers, the study was also supported by the Domžale-Kamnik central purifying plant, a long-term partner of the National Institute of Biology, which collected waster water samples.

The article is available at