Across the United States and the globe, scientists are racing to develop a vaccine and a treatment to contain the novel coronavirus. (Video: The Washington Post)

Governments intensified their efforts Sunday to combat the global spread of the novel coronavirus, as Saudi Arabia followed Italy in enacting new travel restrictions, Iran suspended flights to Europe, and the United States, where the number of cases topped 500, warned citizens against cruise travel.

Uncertainty continued to permeate the response effort, however, amid muddled directives from the Trump administration and reports of some patients unable to access testing. A virus-stricken cruise ship made its way to California to dock — only for Housing and Urban Development Secretary Ben Carson to decline to discuss the details of the federal response plan during a national television interview.