(CNN) – Searing heat may have played a role in the infections of five workers who fell ill last week while culling a large flock of chickens infected with the H5N1 virus in Colorado, health officials said Tuesday.

“At the time transmission is thought to have occurred, Colorado was experiencing 104-plus-degree heat,” and it was probably hotter inside the barns, said Dr. Nirav Shah, principal deputy director of the US Centers for Disease Control and Prevention. The CDC is investigating the outbreak along with the Colorado Department of Public Health and Environment. This made the use of personal protective equipment a challenge, Shah said. (Read More)