There are more cases of whooping cough in Minnesota than at any time in 65 years, according to data released by the Minnesota Department of Health.
From the start of the year until July 20, there have been 1,881 reports of whooping cough in Minnesota. That number is higher than any year since 1947, although the state's population is significantly higher now. There have been no deaths to date in Minnesota this year.
Whooping cough, also known as pertussis, can cause sufferers to cough so violently that they break ribs or vomit, said Kris Ehresmann, DHS director of infectious diseases.
Over the last 50 years, vaccines kept pertussis in check.
The number of pertussis cases is rising across the country. The Centers for Disease Control and Prevention reports that over 18,000 cases have been reported nationwide so far in 2012. Nine children have died.
"Pertussis is a disease that is cyclical, so, typically every three to four years, we'll see a peak in pertussis incidents," Ehresmann said. "But what's been happening over the last several peaks is that those peaks have been escalating."
The vaccine is most important for infants and small children, who are more likely to die from pertussis, Ehresmann said. Most infants in Minnesota are vaccinated against pertussis.
However, the vaccine's effectiveness can wear off, which explains an increase in cases of pertussis among pre-teens.
"We know that within three to four years, they'll start to have some waning immunity," she said. "By the time they get to adolescence, their protection could have completely declined."
Ehresmann said everyone, especially small children and those who spend time around them, should be vaccinated against pertussis.
Another possible reason for part of the disease's resurgence is the increased number of parents who choose not to get their children vaccinated. In the 2011-2012 school year, 1 percent of school-enrolled students in Minnesota lacked vaccinations because their parents decided against it.
Ehresmann said her department seeks to debunk unsubstantiated rumors that vaccines lead to autism.
"The preponderance of evidence suggests that those are not issues related to vaccination," Ehresmann said. "We continue to want to educate parents that vaccines — they're not perfect — but they're safe, and they're certainly a better option than the diseases they prevent."