Cold weather has forced West Nile virus into hibernation, but research on the mosquito-borne illness is heating up.
Colorado State University scientists are retracing the path of the virus in hopes of answering questions about why certain animals are vulnerable to the disease.
About 380 horses statewide were infected after the virus was discovered in the state in August.
The virus was also found in birds, including some at two zoos.
Twelve human cases have been confirmed in Colorado.
One research project will focus on infected horses in Colorado and Nebraska. The rate of infection among horses has been higher in the West than other parts of the country.