The nation’s public health agency says it’s beefing up the ability of labs around the country to test for the Zika virus, which has now infected more than 3,100 people in the U.S.

The Centers for Disease Control and Prevention announced Tuesday it has sent materials to labs in 43 states, the District of Columbia and Puerto Rico allowing them to conduct a Zika test that detects antibodies to fight the virus. So far, labs in 41 of the states, along with D.C. and Puerto Rico, have completed the process required to start testing.