The number of whooping cough cases in Indiana has doubled in the past year, state health officials warned on Thursday, urging parents to make sure their children are vaccinated.

There were 136 confirmed cases of whooping cough in the state, including one that was fatal, in the first half of 2017 — compared with 66 cases, none of them fatal, in the first half of 2016, according to the Indiana State Department of Health.

While the spike was startling, Dr. James D. Cherry, a whooping cough expert at the University of California, Los Angeles’s David Geffen School of Medicine, said it was not particularly worrying. Whooping cough rates tend to be cyclical, he noted, peaking every three years on average. And although a study in 2016 found a correlation between vaccination rates and the rates of both whooping cough and measles, confirmed cases have also risen because of increased awareness and better diagnostic tests.

Nonetheless, Aurora Le, project coordinator of the Biosafety and Infectious Disease Training Initiative at Indiana University School of Public Health in Bloomington, said she “cannot stress enough” the importance of administering childhood vaccines on a standard schedule. “Whooping cough and measles, especially, are two of the most preventable infectious diseases in the Western world,” she said.