The number of whooping-cough cases in California is now at an epidemic level, state health officials said Friday.

More than 800 whooping-cough cases were reported over the past two weeks, suggesting that the infection, which is also known as pertussis, is spreading rapidly, according to a statement by the California Department of Public Health.

As of June 10, there were 3,458 reported cases — more than in all of 2013. There have been two reported infant deaths.

The infection is cyclical and peaks every three to five years, officials said. The previous whooping-cough peak was in 2010, when an epidemic struck 9,159 people and killed 10 infants in the state.

Infants are most susceptible to the disease, so parents are encouraged to vaccinate their children as early as possible. Pregnant women are also encouraged to get vaccinated.

The disease has also raised national concerns. Although California is the only state to declare an epidemic, there has been a 24 percent increase of reported pertussis cases nationally from this time last year, according to the federal Centers for Disease Control and Prevention.

Whooping cough begins with cold-like symptoms and can progress to severe coughing fits that leave people gasping for breath.

California officials said they were working closely with local health departments and schools to inform the public of the importance of vaccinations.