The Centers for Disease Control and Prevention is now calling the number of whooping cough cases through the country an epidemic.

Wisconsin has had more than 3,000 so far this year. There have been 18,000 across the country. If the cases continue to climb, it could rival 1959, when 40,000 illnesses were reported for the year.

In Marathon County, the health department has investigated 380 cases. In a normal year, they see about 12.

An epidemiologist says whooping cough, or pertussis, tends to appear in a cyclical nature, and there are some theories as to why this year the cases have spiked.

"There is a theory that the new acellular type does not produce as good of an immune response and that it wears off more quickly," Ruth Marx said.

She says some of those who've gotten the illness have been age-appropriately vaccinated, but the vaccine is only 75 to 80 percent effective.

Those who have been vaccinated and still get pertussis have a milder version, but that presents another problem.

Since those individuals aren't as sick, they're going about their normal routine while exposing others.

Pertussis is most dangerous to infants, the elderly and those with compromised immune systems.

Marx says the health department recommends all individuals get pertussis vaccines, and adults get boosters.