Viruses could become harder to kill

Most of the pathogenic viruses in lakes are naturally rendered harmless by sunlight, warm temperatures and bacteria normally present in the water. But a team of scientists at EPFL’s Environmental Chemistry Laboratory (LCE), within the School of Architecture, Civil and Environmental Engineering (ENAC), has found that some human enteroviruses – which can cause gastro-intestinal infections or severe diseases such as meningitis, and are found in feces, meaning they could make their way into wastewater effluent – may have the capacity to adapt to higher water temperatures. The study was led in collaboration with a scientist from the Swiss Federal Institute of Aquatic Science and Technology, Eawag.

Resistant to disinfectants

In their study, the research team created four human enterovirus populations by incubating samples in lake water at 10°C and 30°C in both the presence and the absence of sunlight. They found that the viruses surviving in the warmer water became increasingly resistant to temperature, unlike those in the colder water.

The scientists’ findings have just been published in Environmental Science and Technology.

A consequence of globalization

What’s more, the chances of resistant viruses traveling from one world region to another are growing as a result of globalization, since people and goods (like fruits and vegetables), which could potentially be contaminated, are moving about more readily. For example, a pathogen that is perfectly adapted to the warm water of an equatorial region could inadvertently be carried into Switzerland, where it is likely to survive for a long time because it would be resistant to the ambient temperatures. This would heighten the risk of the virus spreading a benign disease or a more serious one like polio.

“The other implication of our study is that if temperatures rise, there could be more world regions where viruses develop this capability to resist,” says Kohn. That wouldn’t be a direct consequence of global warming – because even a 3°C rise would be too small to make a difference – but of an increase in the number of long heat waves. The next step for the research team will be to test their findings in a series of field experiments.