Washington state has seen more than 430 cases of pertussis, also called whooping cough, this year, in comparison to 378 at this time last year, according to the Washington State Department of Health.

Whidbey Island has confirmed just one case, said Island County Public Health Officer Roger Case.

“This is a little bit below normal for the disease but we shouldn’t let our guard down,” Case said last week.

The rate of whooping cough in babies is nearly 10 times greater than the rate of all other ages combined in Washington, according to the DOH. Twenty-two babies were hospitalized, including two who died.

Whooping cough is very contagious and spreads easily from person to person through coughing and sneezing. It causes coughing spells so severe that it’s hard for infants to eat, drink and breathe. These spells can last for weeks. It can lead to pneumonia, seizures and even death, according to the DOH.

Adults may have milder symptoms than babies and may mistake their symptoms for a cold or persistent cough while continuing to spread the illness.

“The disease is mainly spread by adults that don’t know they have it because they think it’s a child’s disease,” Case said, adding that people should get checked if they’ve been coughing for two to three weeks.

Immunization is key. After a severe outbreak of whooping cough on Whidbey Island three years ago, most children were immunized, contributing to the low level of cases on the island now, Case said.

Teenagers and adults should get the Tdap booster immunization, especially grandparents and others who are around children often, Case said.