West Nile Virus Reported in Majority of US States

The number of human cases of West Nile virus continues to rise around the United States; now, more than 80% of states have reported detecting the virus so far this season.

The Centers for Disease Control and Prevention (CDC) is reporting that, as of August 8, 2017, 42 states along with the District of Columbia have reported cases of West Nile virus infection in either birds, mosquitoes, or humans. Of the 159 human cases of the virus reported so far this season, 91 were classified as neuroinvasive, resulting in illness such as meningitis or encephalitis, while 68 cases were non-neuroinvasive. While severe symptoms, such as neuroinvasive disease, occur in only about 1% of all West Nile cases, as many as 80% of those infected with the virus do not present with any symptoms of illness, and thus, those cases are more likely to go unreported. Based on CDC data, Maine, New Hampshire, and Rhode Island are among the only states that haven’t reported any West Nile activity yet for 2017.

In Pennsylvania, Department of Health officials reported the state’s first probable human case of West Nile virus on August 8, 2017. The case involves a resident of Montgomery County, but health officials have yet to release any details on the current health status of the individual. While a number of Pennsylvania counties have no active West Nile surveillance programs, 38 counties this season have reported detecting either birds, mosquitoes, or humans positive for the virus.

“Detecting the first human case of West Nile Virus this year serves as a great reminder for Pennsylvanians to take the proper precautions when they are outside or near areas where mosquitoes are prevalent,” said Rachel Levine, MD, Pennsylvania’s acting secretary of health and physician general, in a recent statement. “There are some simple steps you can take to protect yourself and your loved ones from mosquito-related diseases.” Such steps include removing standing water from plastic kiddie pools and wheelbarrows, and drilling holes in the bottom of recycling bins so that they don’t collect water for mosquitoes to breed in.

Additional human cases of West Nile were reported in Reno, Nevada, on August 2, 2017 by the Washoe County Health District and in Idaho’s Kootenai County by the Idaho Department of Health and Welfare; these are the first human cases of the virus for both states thus far this summer season. The case in Reno involved a local resident who had traveled outside of the county, so although West Nile-positive mosquito pools had been detected in the area, local health officials could not confirm where the resident became exposed to the virus. The case reported in Idaho’s Kootenai County on August 3, 2017, occurred in a resident over the age of 50, who became ill with neuroinvasive disease as a result of the infection but was reported to be recovering from the illness.

“West Nile activity has ramped up significantly during the last few weeks, so people are strongly encouraged to fight the bite of mosquitoes to protect themselves and their families,” said Idaho’s state public health veterinarian, Leslie Tengelsen, PhD, DVM, in a recent statement. “This is a good warning for all of us to take protective measures, including wearing insect repellent and reducing mosquito habitat, such as standing water, around our gardens and homes.”