Mosquitoes collected in Weld County have tested positive for West Nile virus, the mosquito-borne disease that can cause fever and headaches, and in some cases lead to encephalitis, a brain infection.

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The positive tests represent the first confirmed case of the virus in the Colorado this year, and officials said the mosquitoes are more pregnant now than ever. The virus was found in Culex mosquitos, a type that can carry a variety of diseases and are the most common mosquito found in urban areas in the U.S.

“The increasing hot weather and afternoon thunderstorms have created favorable conditions for the Culex mosquito that carries West Nile virus,” Mark Lawley, executive director fo the Weld County Health Department, said in a statement. 

The number of Culex mosquitoes in the county now is three times higher than the 5-year average, according to a news release from the county’s health department. 

As of Wednesday, no humans have contracted the virus in Weld County, but that could change and as a result officials are urging residents to be aware of the risk. 

“The public needs to be vigilant because West Nile virus has a permanent summer presence in Colorado,” Lawley said. 

Symptoms of the virus can appear between three and 14 days after infection and include fever, headache, nausea and vomiting, muscle aches, weakness and a rash. Most people don’t show any symptoms of the virus, officials said. 

If someone develops symptoms they are urged to seek medical treatment immediately. In less than 1% of each infection people have developed a a sometimes fatal, nervous system illness. No medication exists to treat the disease nor is there a vaccine to prevent infection.

Health officials recommend using the four “D’s” to prevent mosquito bites:

• DRAIN standing water around your house weekly, including from tires, cans, flowerpots, clogged rain gutters, rain barrels, toys and puddles.
• DUSK and DAWN are when mosquitoes are most active. Limit outdoor activities and take precaution to prevent mosquito bites during these times
• DEET is an effective ingredient to look for in insects repellents. Other repellents containing pinardin, IR3535, oil of lemon eucalyptus, or para-menthane-diol are also effective against mosquitoes.
• DRESS in long sleeves and pants, and a hat, in areas where mosquitoes are active.

Those interested in learning more about preventing mosquito bites and the West Nile virus can click here.