Human viruses are ubiquitous contaminants in surface waters, where they can persist over extended periods of time. Among the factors governing their environmental persistence, the control (removal or inactivation) by microorganisms remains poorly understood. Here, we determined the contribution of indigenous bacteria and protists to the decay of human viruses in surface waters. Incubation of echovirus 11 (E11) in freshwater from Lake Geneva and seawater from the Mediterranean Sea led to a 2.5-log₁₀ reduction in the infectious virus concentration within 48 h at 22°C, whereas E11 was stable in sterile controls. The observed virus reduction was attributed to the action of both bacteria and protists in the biologically active matrices. The effect of microorganisms on viruses was temperature dependent, with a complete inhibition of microbial virus control in lake water at temperatures of ≤16°C. Among three protist isolates tested (Paraphysomonas sp., Uronema marinum, and Caecitellus paraparvulus), Caecitellus paraparvulus was particularly efficient at controlling E11 (2.1-log₁₀ reduction over 4 days with an initial protist concentration of 10³ cells ml^–1). In addition, other viruses (human adenovirus type 2 and bacteriophage H6) exhibited different grazing kinetics than E11, indicating that the efficacy of antiviral action also depended on the type of virus. In conclusion, indigenous bacteria and protists in lake water and seawater can modulate the persistence of E11. These results pave the way for further research to understand how microorganisms control human viral pathogens in aquatic ecosystems and to exploit this process as a treatment solution to enhance microbial water safety.

IMPORTANCE Waterborne human viruses can persist in the environment, causing a risk to human health over long periods of time. In this work, we demonstrate that in both freshwater and seawater environments, indigenous bacteria and protists can graze on waterborne viruses and thereby reduce their persistence. We furthermore demonstrate that the efficiency of the grazing process depends on temperature, virus type, and protist species. These findings may facilitate the design of biological methods for the disinfection of water and wastewater.

人病毒是地表水中普遍存在的污染物，它们可以在很长一段时间内持续存在。在控制其环境持久性的因素中，对微生物的控制（去除或灭活）仍然知之甚少。在这里，我们确定了本地细菌和原生生物对人类病毒在地表水中衰变的贡献。回声病毒11（E11）在日内瓦湖的淡水和地中海的海水中的孵育导致2.5 log ₁₀在22°C下48小时内感染性病毒浓度降低，而E11在无菌对照中稳定。观察到的病毒减少归因于细菌和原生生物在生物活性基质中的作用。微生物对病毒的影响取决于温度，在≤16°C的温度下，完全抑制了湖水中微生物对病毒的控制。在测试的三个原生质分离株中（副藻，Uronema marinum和小白蜡虫），小白蜡虫在控制E11方面特别有效（初始原虫浓度为10 ³细胞ml ^–1，在4天内减少了2.1 log _10）。）。此外，其他病毒（2型人类腺病毒和噬菌体H6）表现出与E11不同的放牧动力学，表明抗病毒作用的功效也取决于病毒的类型。总之，湖水和海水中的本地细菌和原生生物可以调节E11的持久性。这些结果为进一步研究奠定了基础，以了解微生物如何控制水生生态系统中的人类病毒病原体，并将这一过程用作提高微生物水安全性的处理解决方案。

重要信息水性人类病毒会长期存在于环境中，对人类健康构成威胁。在这项工作中，我们证明了在淡水和海水环境中，本地细菌和原生生物都可以在水传播的病毒上吃草，从而减少其持久性。我们进一步证明放牧过程的效率取决于温度，病毒类型和原生物种。这些发现可能有助于设计用于水和废水消毒的生物方法。