By Melissa Garcia

LARIMER COUNTY, Colo. (CBS4) – A record number of mosquitoes are testing positive for the West Nile virus in Boulder, Weld, and Larimer counties.

Officials said that between 80 and 90 percent of the insects tested last week were the type of mosquito with the potential to carry the deadly disease — culex mosquitoes.

Colorado has seen 13 cases in humans so far in 2016.

The state’s first West Nile virus death was announced last week.

Health officials said that while many regions of Colorado are seeing fewer mosquitoes this year than last, the disease is far more active this year.

The culex genus mosquito, the carrier of the West Nile virus, is separated from other mosquitos in a lab in Arizona in 2004 (credit: Jeff Topping/Getty Images)

The culex genus mosquito, the carrier of the West Nile virus, is separated from other mosquitos in a lab in Arizona in 2004 (credit: Jeff Topping/Getty Images)

Fort Collins residents took cover inside their homes on Monday and Wednesday as trucks sprayed pesticides to kill mosquitoes on contact.

“The sooner the better,” said Mary Ruhlman, a Fort Collins resident. “We need to have the neighborhood sprayed if we have West Nile.”

Her neighborhood was one of three high-risk zones sprayed in Larimer County.

Researchers at Colorado Mosquito Control were seeing a surge in the number of mosquitoes infected with the West Nile virus.

Up to 90 percent of the species trapped over the last week were the type that can carry and transmit the virus, compared to just 10 percent last year.

“West Nile virus is a concern,” said Michael Orcutt, another Fort Collins resident. “If there’s any chance of mosquitoes being out, we normally stay inside.”

(credit: CBS)

(credit: CBS)

While the Zika virus may be the topic of concern on many minds, state health experts said that West Nile was the real risk in Colorado.

“This is a virus that can be deadly to people. It is here. We’re not going to get rid of it. We know it’s here, it is in our bird population. And unfortunately, every summer, we do see cases,” said Jennifer House, a spokesperson with the Colorado Department of Public Health and Environment.

The recent spraying was believed to be only the second time mosquito control has sprayed in Fort Collins in the last decade.

(credit: CBS)

(credit: CBS)

Officials said that they may need to spray again in the next couple months, while the risk is still high before the first freeze of the season.

“I’m surprised that Fort Collins has a higher standard for spraying than the county does,” Orcutt said. “I just wish they would spray more often.”

Health authorities said that the best way to protect against the West Nile virus was to use an insect repellent with DEET. Residents should also drain any standing water from their properties. Even a tablespoon of water can become a breeding ground for mosquitoes.

LINK: Colorado Department of Health’s West Nile Virus Page

Additional Information From The Colorado Department Of Public Health And Environment

To help prevent West Nile virus infection, follow the four D’s:

– DRAIN standing water around your house weekly. Remember to drain water 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 precautions to prevent mosquito bites during these times.
– DEET is an effective ingredient to look for in insect repellents. Always follow label instructions carefully.
– DRESS in long sleeves and pants in areas where mosquitoes are active.
For more information about West Nile virus, visit FightTheBiteColorado.com.

Check out Dr. Dave Hnida’s recent blog entry on how to protect yourself against West Nile.

Melissa Garcia has been reporting for CBS4 News since March 2014. Find her bio here, follow her on Twitter @MelissaGarciaTV, or send your story idea to mkgarcia@cbs.com.