FORT COLLINS, Colo. -

Larimer County health officials say this year's outbreak of the West Nile virus is the worst in years.

Health officials say 30 people have been infected with virus so far this year and those numbers are expected to climb.
    
The virus was first reported in the United States in 1999, according to the Centers for Disease Control and Prevention.
    
Human infections from the mosquito-borne disease can occur without symptoms or can cause mild or severe illness, fever and aches. Infections can also lead to disability and even death.