West Nile Virus activity apparently on the rise in Butte County. Officials Monday said 11 humans have tested positive for the virus. The increasing number of mosquito pools and dead birds are having an effect. County mosquito officials say people should take all precautions to deal with the causes of the virus. Since West Nile was first detected in Butte County 10 years ago, there have been 139 human infections, with 7 deaths.