First Human Case of West Nile Reported in the Centennial State

Following the recent announcement reporting the first human case of West Nile virus of the season in Colorado, health officials there, and around the country, are emphasizing the importance of mosquito control and bite prevention in the summer months.

The Centers for Disease Control and Prevention (CDC) reports that in 2016, the United States saw 2,039 human cases of West Nile virus; of those cases, 149 occurred in Colorado, resulting in 8 deaths. The areas that were hardest hit were the state’s Boulder, Larimer, and Weld counties, which saw 82 human cases of the virus collectively. Colorado reported its first West Nile case in 2002, and the following year, the state reported 2,947 human cases—its highest number of reported cases since the virus first appeared there. Health officials in the state note that while they likely can’t eradicate West Nile in Colorado for good, mosquito control efforts have helped to minimize the impact of seasonal outbreaks and mitigate the number of human infections.

On June 30, 2017, the Colorado Department of Public Health and Environment (CDPHE) reported the state’s first human West Nile case of the season. The Denver Post reported that the case occurred in a Jefferson County resident who was recovering at home. Since state health officials began conducting weekly mosquito testing on June 12, 2017, they’ve detected West Nile virus-positive mosquitoes in Larimer County. While the higher elevation areas of Colorado’s Rocky Mountains experience shorter transmission seasons, and thus, see a reduced risk of West Nile, the Culex mosquito species that commonly carries the virus can be found at elevations as high as 10,000 feet. Therefore, officials are reminding state residents as well as visitors to take preventive measures against infection.

“When the virus is present, people are at risk,” Jennifer House, DVM, MPH, a Colorado public health veterinarian, said in a recent statement. “Protecting yourself from mosquito bites is the number 1 way to avoid getting any mosquito-borne illness. Use an effective insect repellent, wear protective clothing or stay indoors when mosquitoes are active, and mosquito-proof your home.” The CDPHE is reminding the public that those over the age of 60 or who have certain medical conditions are at greater risk of developing series illness from West Nile, and thus, should take extra precautions against mosquitoes.

Along with the news from Colorado, on June 30, 2017, the California Department of Public Health reported the state’s third human case of West Nile virus of the season, which occurred in Kern County. The case is the county’s first human case of the season, and involved a resident living near Bakersfield. So far this season, Kern County has reported 7 mosquito samples testing positive for West Nile.

As some states are managing their first human cases, states such as Massachusetts, have just recently reported their first West Nile-positive mosquitoes, prompting calls from state health officials for residents to mosquito proof their homes and protect animals such as horses, as they, too, can fall ill with West Nile virus.