A virus spread by biting midges never before seen in Switzerland is thought to be responsible for a surge in sickness in Swiss dairy cows, authorities said Monday. Several Swiss regions have recorded a spike in illnesses since mid-July, with cows suffering from fever and diarrhoea and producing less milk, the Federal Food Safety and Veterinary Office (FSVO) said. Orthobunyaviruses of the Simbu group are primarily transmitted by biting midges, and no vaccines are currently available, the FSVO said. Advertisement"It is currently unclear whether there is a connection between the current heatwave and the reported cases of illness," it added. "However, high temperatures pose a significant stress, especially for high-yielding dairy cows, and can make them more susceptible to disease."