The COVID-19 outbreak has forced countries to introduce severe restrictive measures to contain its spread. In particular, physical distancing and restriction of movement have had important consequences on human behaviour and potentially also on illicit drug use and supply. These changes can be associated with additional risks for users, in particular due to reduced access to prevention and harm reduction activities. Furthermore, there have been limitations in the amount of data about drug use which can be collected due to restrictions. To goal of this study was to obtain information about potential changes in illicit drug use impacted by COVID-19 restrictions. Wastewater samples were collected in seven cities in the Netherlands, Belgium, Spain and Italy at the beginning of lockdowns (March-May 2020). Using previously established and validated methods, levels of amphetamine (AMP), methamphetamine (METH), MDMA, benzoylecgonine (BE, the main metabolite of cocaine) and 11-nor-9-carboxy-Δ⁹-tetrahydrocannabinol (THC-COOH, main metabolite of tetrahydrocannabinol (THC)) were measured and compared with findings from previous years. Important differences in levels of consumed drugs were observed across the considered countries. Whilst for some substances and locations, marked decreases in consumption could be observed (e.g., 50% decrease in MDMA levels compared to previous years). In some cases, similar or even higher levels compared to previous years could be found. Changes in weekly patterns were also observed, however these were not clearly defined for all locations and/or substances. Findings confirm that the current situation is highly heterogeneous and that it remains very difficult to explain and/or predict the effect that the present pandemic has on illicit drug use and availability. However, given the current difficulty in obtaining data due to restrictions, wastewater analysis can provide relevant information about the situation at the local level, which would be hard to obtain otherwise.

COVID-19疫情迫使各国采取严格的限制性措施来遏制其蔓延。特别是，身体疏远和行动受限对人类行为以及潜在的非法药物使用和供应都产生了重要影响。这些变化可能给用户带来额外的风险，尤其是由于减少了预防和减少危害活动的机会。此外，由于限制，可以收集的有关药物使用的数据量也受到限制。这项研究的目的是获得有关受COVID-19限制影响的非法药物使用的潜在变化的信息。在封锁开始之时（2020年3月至5月），在荷兰，比利时，西班牙和意大利的7个城市中收集了废水样本。⁹测量了四氢大麻酚（THC-COOH，四氢大麻酚（THC）的主要代谢产物）并将其与前几年的发现进行了比较。在所审议的国家中，人们观察到毒品消费水平的重要差异。尽管对于某些物质和地点，可以观察到消费量显着下降（例如，与往年相比，MDMA水平下降了50％）。在某些情况下，可以发现与前几年相近甚至更高的水平。还观察到每周模式的变化，但是并未针对所有位置和/或物质明确定义这些变化。调查结果证实，目前的情况高度不同，并且仍然很难解释和/或预测目前的流行对非法药物的使用和可获得性的影响。然而，