A cache of internal emails offers a look at the pressure the nation’s public health officials faced from the new health secretary in the early months of the Trump administration.

© Haiyun Jiang for The New York Times

In a tense congressional hearing, the health secretary also said he bore no responsibility for the measles outbreak in the United States.

© Haiyun Jiang/The New York Times

Dr. Jay Bhattacharya will serve as the acting director of the Centers for Disease Control and Prevention until President Trump appoints a permanent director.

© Eric Lee/The New York Times

A former director of the Centers for Disease Control and Prevention and a former chief medical officer of the agency will advise the state on public health issues.