MOSCOW—Russia warned on Monday of a possible increase in West Nile virus infections this autumn as mild temperatures and heavy precipitation create favorable conditions for the mosquitoes that carry it. Originally from Africa, the virus has spread in Europe, Asia, and North America. It is mainly transmitted through mosquito bites and can lead to a fatal neurological disease in humans, although most people infected never develop any symptoms. Scientists have said that milder temperatures attributed to climate change could cause diseases such as the West Nile virus to become more widespread. “In light of favorable climatic conditions this year—an abundance of precipitation … a warm and long autumn, a high number of [virus] carriers could be observed in the autumn,” Rospotrebnadzor, Russia’s consumer health watchdog, said. The virus causes West Nile fever in around 20 percent of cases, the World Health Organization (WHO) has said. It is related to the …