West Nile virus has been found in another mosquito sample in Rhode Island. The state’s Department of Environmental Management said Friday that the sample from Charlestown is the fourth time this year that mosquitoes with the virus have been found in the state. The state said the findings are not unexpected this time of year. On Thursday the state said another mosquito sample taken in Barrington had tested positive for Eastern equine encephalitis. Officials also announced this week the diagnosis of the state’s first human case of West Nile fever, in a Newport County man in his 50s. He has recovered.