The US contributes around a fifth of the budget for the World Health Organization – its withdrawal from the public health body will impede efforts to control the global spread of diseases and could pu

Ooh, that’s a big one,” Donald Trump said Monday as he signed an executive order – one of dozens during his first hours as president – to withdraw the United States from the World Health Organization.

It’s an action many scientists fear could roll back decadeslong gains made in fighting infectious diseases like AIDS, malaria and tuberculosis.