The alarm sounded by county and state health officials about whooping cough isn’t alarmist. The threat, especially to young babies, is real and potentially lethal. The call for everyone — children and adults — to be vaccinated needs to be heeded.

Whooping cough, also known as pertussis, was declared an epidemic in Washington last month. It has hit especially hard in Snohomish County, where more cases were reported in the first four months of this year than in all of 2011.

Infants, who can’t receive their first vaccination until they’re about 2 months old, are particularly vulnerable to the disease. It can cause a number of serious problems, including pneumonia, seizures, breathing trouble, and even death.

It’s less of a threat to adults, but they can transmit whooping cough to infants. Last year, a 27-day-old baby girl from Lake Stevens died after contracting whooping cough from her mother.

That’s why it’s so critical for everyone to get a shot of protection. And since immunizations only last about 10 years, it’s important for adults to check with their doctor to see when they were last vaccinated.

Adults who have insurance but haven’t been to a doctor in the past year have another good reason to make an appointment for a physical exam. A single shot during that visit can protect against tetanus, diphtheria and pertussis for a decade. A physical isn’t required to get the shot, but it’s a good idea to have one regularly.

Low-cost or free vaccines are available for uninsured adults. For options, visit the Snohomish Health District website at www.snohd.org/Shd_CD/CDcontrol.aspx.

This is the first epidemic declared by state Health Secretary Mary Selecky in her 13 years in office. Given how rapidly the pertussis outbreak was spreading, she told the Associated Press, she felt she had to take action.

Now it’s up to individuals to take action. Whooping cough is spread through person-to-person contact. Even an adult who isn’t in direct contact with infants can transmit the disease to an adult who is. Historical patterns show that pertussis is cyclical, with cases growing every three to five years as vaccines wear off, and subsiding as more adults get shots. The current cycle has been particularly harsh.

This epidemic won’t go away on its own. Our youngest children are at risk. This isn’t a warning responsible adults can ignore. The responsible choice is to get vaccinated.