Denver sees first case of West Nile virus

The first case of West Nile virus has been found in a Denver resident, Denver Public Health and Environment confirmed.

So far, the 2024 West Nile season is on track to be way less dangerous than last year’s unusually high count, which followed a wet spring and early summer.

So far this year, 14 Coloradans have contracted the virus. Of those, seven have been hospitalized and no one has died from West Nile, according to the state public health website.

In 2023, 51 Coloradans were killed by the mosquito-transmitted West Nile Virus among 634 documented cases – an 8% death rate and the highest number of deaths since the record-setting year of 2003 when the virus caused 66 deaths. It's also worth noting that there were 386 hospitalizations related to the virus last year. The death toll of 2023 was far above the average number of deaths for the previous 10 years — 7.7 deaths annually.

The Colorado Department of Health and Environment reported that as of this week, counties where residents have contracted the virus are Arapahoe, Kit Carson, La Plata, Mesa, Weld and Larimer. Arapahoe and Weld counties have seen the most cases with three each.

The type of mosquito which carries West Nile virus, called Culex, lay their eggs in standing water, which could be as small as a backyard flower-pot or as large as a fresh-water lake.

They breed in over-watered lawns and they are attracted to the smell of carbon dioxide and sweat, which means that joggers and bicyclists are prime candidates for infection.

Once eggs are laid, they have been known to take only two days to hatch.

In Colorado, most West Nile virus cases are diagnosed in August and September, but cases can be identified as early as May and as late as December. Generally, the mosquito season extends from late-April until mid-October, with the end usually signaled by the first freeze in the fall.

There is no cure for the West Nile virus in humans, but there is a vaccine for horses, which are hit particularly hard by the disease.

This story was written with the help of OutThere Colorado writer Spencer McKee.