9 babies have died from whooping cough in California

The foreign affairs department said a number of American states had been hit by the disease including California, where local reports say nine babies have died.

"Several US states have reported an increase in cases and/or localised outbreaks of pertussis (whooping cough), including a state-wide epidemic in California," the travel advice says.

"The United States government's Centers for Disease Control and Prevention advises it is not necessary to delay travel to an area that is experiencing a pertussis outbreak, but visitors should make sure they are up to date on their vaccines."

The department maintained its overall advice at "exercise caution", the second of a five-level warning system.

A report on the Los Angeles Times website posted on Tuesday said a ninth baby had died from whooping cough, making it the deadliest outbreak in California in five years.

Whooping cough is a highly contagious bacterial infection affecting the lungs which is usually relatively mild in adults but has a high mortality rate among children.