The move makes Illinois the second US state to join the program in defiance of Republican President Donald Trump after California, also led by a Democratic governor, joined in January.

The US formally left the WHO last month after completing a one-year waiting period following an executive order that Trump signed on his first day back in office in January 2025.

“I refuse to sit by as Donald Trump undermines science and weakens our nation’s ability to detect and respond to global health threats,” Pritzker, an outspoken Trump critic, said in a post on social media website X.

“By joining the World Health Organization’s coordinated network, GOARN, we are ensuring that our public health leaders – and the public – have the information, expertise, and partnerships they need to protect the people of our state,” Pritzker said in a statement.

The network responds to public health events around the world, such as pandemics and disease outbreaks, and comprises more than 360 technical institutions.