UNDATED (WTAQ) – Wisconsin U.S. Senator Ron Johnson is asking the head of the Centers for Disease Control and Prevention seeking more information on how the agency is dealing with the bacterial outbreak Elizabethkingia.

In a letter sent Tuesday to CDC director Thomas Frieden, M.D., Johnson is asking what steps they are taking to find the source of the rare bloodstream infections.

At least 17 people have died in Wisconsin and Michigan from Elizabethkingia, while another 52 confirmed cases exist in the Badger State.

Health officials say most of the people affected are over age 65 with underlying health problems.

So far it’s unclear where the infections came from, but the CDC previously tested and ruled out health care products, water sources and the environment.

Johnson’s letter gives Frieden and the CDC until April 5 to provide answers to his questions.