The COVID-19 pandemic has induced dramatic effects on the population of the industrialized north of Italy, whereas it has not heavily affected inhabitants of the southern regions. This might be explained in part by human exposure to high levels of fine particulate matter (PM) in the air of northern Italy, thus exacerbating the mortality. Since trees mitigate air pollution by intercepting PM onto plant surfaces and bolster the human immune system by emitting bioactive volatile organic compounds (VOCs), we hypothesize a protective role of evergreen forested areas in southern Italy. We compared the mortality rate due to COVID-19, the death number, the positivity rate and the forest coverage per capita in various Italian regions. Hectares of forest per capita and prevalence of deciduous versus evergreen forestal species were also estimated. In silico docking studies of potentially protective compounds found in Laurus nobilis L., a typical Mediterranean plant, were performed to search for potential antivirals. We found that the pandemic’s severity was generally lower in southern regions, especially those with more than 0.3 hectares of forest per capita. The lowest mortality rates were found in southern Italy, mainly in regions like Molise (0.007%) and Basilicata (0.005%) where the forest per capita ratio is higher than 0.5 Ha/person. Our findings suggest that evergreen Mediterranean forests and shrubland plants could have protected the southern population by emission of immuno-modulating VOCs and provision of dietary sources of bioactive compounds. Moreover, in silico studies revealed a potential anti-COVID-19 activity in laurusides, which are unexplored glycosides from bay laurel. Overall, our results highlight the importance of nature conservation and applications to the search for natural antivirals.

COVID-19 大流行对意大利北部工业化地区的人口产生了巨大影响，但并未严重影响南部地区的居民。这可能部分是由于人类暴露于意大利北部空气中高水平的细颗粒物 (PM)，从而加剧了死亡率。由于树木通过将 PM 拦截到植物表面来减轻空气污染，并通过释放具有生物活性的挥发性有机化合物 (VOC) 来增强人体免疫系统，因此我们假设意大利南部常绿森林地区的保护作用。我们比较了意大利各个地区因 COVID-19 导致的死亡率、死亡人数、阳性率和人均森林覆盖率。还估计了人均森林面积和落叶与常绿森林物种的流行率。Laurus nobilis L.，一种典型的地中海植物，被用来寻找潜在的抗病毒药物。我们发现，南方地区的疫情严重程度普遍较低，尤其是人均森林面积超过 0.3 公顷的地区。意大利南部的死亡率最低，主要是在莫利塞（0.007%）和巴西利卡塔（0.005%）等地区，人均森林比率高于 0.5 公顷/人。我们的研究结果表明，常绿的地中海森林和灌木丛植物可以通过释放免疫调节 VOC 和提供生物活性化合物的饮食来源来保护南方人口。此外，在计算机研究中揭示了月桂苷中潜在的抗 COVID-19 活性，月桂苷是月桂中未开发的糖苷。总体而言，我们的结果突出了自然保护和应用在寻找天然抗病毒药物中的重要性。