PIERRE, S.D. (AP) — State health officials are reminding residents to use mosquito repellent and take other precautions to protect themselves against West Nile virus.

State epidemiologist Lon Kightlinger says neuroinvasive disease can be particularly serious for the elderly and those with health conditions such as cancer, diabetes and high blood pressure or a history of alcohol abuse.

South Dakota as of this week has reported 21 human West Nile cases, followed by California with 18. Ten of South Dakota's cases were neuroinvasive, while the next highest were Minnesota and Mississippi with eight cases each.

Kightlinger said South Dakota has also reported 172 West Nile virus-positive mosquito pools.

He says the virus clearly is circulating in the state, and residents should use mosquito repellents and limit evening exposure by wearing pants and long sleeves.

Copyright 2013 The Associated Press.