It is mosquito season in Montana. Mosquito bites aren’t just annoying. Depending on the species, mosquitos can carry disease. One of those diseases of concern in Montana is West Nile virus (WNV). Montana Department of Public Health and Human Services (DPHHS) recently announced the first two human WNV infections of the summer. In addition to human infections, mosquito pools in several counties have tested positive for the virus and a few counties have reported infections in horses.
The infection often goes unnoticed, as the majority of people have no symptoms. It can cause headache, body aches, joint pain and fever in about 20 percent of those who are infected. Fewer than one percent develop severe illness that can cause swelling of the brain and other neurologic manifestations including death.
WNV arrived in the U.S. in 1999 and reached Montana in 2002. The reported number of infections have varied widely in Montana over the past 17 years, ranging from fewer than two to more than 200 in 2003 and 2007. In 2003, 75 of those human infections were considered neuroinvasive, the more severe form of infection. Montana has had deaths attributed to WNV infection in six of the past 16 years. The two human cases so far this year have been considered neuroinvasive; both people were over 60 years of age and were hospitalized.
