Washington saw more than 11 percent of the nation's pertussis cases during the 2012 epidemic, and ranked fourth in incident rates of the disease.
Data from the federal Centers for Disease Control and Prevention show Washington had a pertussis incident rate of 64.3 cases per 100,000 people -- almost six times the national average of 11.6 per 100,000, as of late November.
Wisconsin had the highest rate with 93.4 cases per 100,000. Minnesota came in second with a rate of 78.1, and Vermont ranked third with a rate of 66.1.
The nation overall saw 41,880 reported cases of the disease, commonly known as whooping cough, across 49 states in 2012 -- the worst year for the disease since the almost 63,000 cases reported in 1955, according to the Associated Press.
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Washington had 4,744 reported cases for the year, making up 11.3 percent of all cases nationally.
That was an almost 500 percent increase compared to the 807 cases reported in 2011, according to state Department of Health data published this week.
Benton County finished the year with 82 reported cases and an incidence rate of 47.4 per 100,000.
Franklin County had 45 reported cases and 59.6 per 100,000 incidence rate, health department statistics showed.
That was about in the middle of the pack for the state. The highest whooping cough rates were seen in Skagit County, with 471.1 cases per 100,000 population. Yakima County was second with 190.7 per 100,000, and Whatcom County was third with a rate of 169.3. No other counties in the state reported triple-digit incidence rates.
Only Garfield County had no reported ccases in 2012.
The lowest rate was seen in Whitman County, which had a rate of 4.6 and was the only county reporting any cases in the single digits.
Pertussis activity peaked around mid-year and has dropped off in the last few months.
Whooping cough, also known as pertussis, is a highly contagious respiratory illness caused by Bordatella pertussis bacteria, and has symptoms similar to a nasty cold -- sneezing, runny nose, fever and cough.
The cough is what makes pertussis distinctive. Children tend to make a whooping sound with a pertussis cough because they're struggling to catch their breath, according to a state health department fact sheet.
But the whooping is less prevalent in adults and teenagers, who may just have a prolonged cough that persists for weeks or even a couple of months.
Complications for infants include pneumonia, ear infection, loss of appetite, brain disorders or death.
Adults and teenagers may develop pneumonia or experience problems sleeping, urine leakage or broken ribs from severe coughing.