PIERRE, S.D. – Culex tarsalis mosquito numbers are increasing across the state and more of the mosquitoes are positive for the West Nile virus (WNV), says a state health official. The Culex tarsalis is the primary carrier of WNV in South Dakota.

“From the first week of July to the second, we saw a substantial increase in Culex mosquitoes and also a rise in the number of West Nile positives,” said Lon Kightlinger, state epidemiologist for the Department of Health. “Those higher numbers mean an increased risk of disease transmission so it’s important that people protect themselves with appropriate repellent.”

Kightlinger noted that historically 90 percent of South Dakota’s WNV cases have occurred from mid-July to mid-September. To date, South Dakota has reported four cases of human West Nile (Brookings, Buffalo, Jones and Spink counties) and 23 positive mosquito pools.

To prevent mosquito bites and reduce the risk of WNV:

• Use mosquito repellents (DEET, picaridin, oil of lemon eucalyptus, or IR3535) and limit exposure by wearing pants and long sleeves in the evening.
• Limit time outdoors from dusk to midnight when Culex mosquitoes are most active.
• Get rid of standing water that gives mosquitoes a place to breed.
• Support local mosquito control efforts.

Personal precautions are especially important for those at high risk for WNV – people over 50, pregnant women, transplant patients, individuals with diabetes or high blood pressure, and those with a history of alcohol abuse. People with severe or unusual headaches should see their physicians.

Find WNV prevention information on the Web at http://westnile.sd.gov.