Pertussis, a disease better known as whooping cough because of the severe coughing fits it causes, is making a resurgence in Kentucky, with recent outbreaks in central and northern parts of the state.
According to the Kentucky Department of Health, 113 cases of the infectious respiratory disease have been reported this year, including outbreaks in Madison, Estill and Fayette counties. The statewide numbers are on pace to surpass last year's total of 168 and continue a spike in numbers that closely follows a national trend.
The bacterial disease particularly affects infants and older children, who are required to receive the five-dose vaccine before entering sixth grade. But the outbreaks have state and local health officials urging "boosters" — immunizations for children and adults 11 and older.
"One of the biggest ways to intercept an outbreak is to offer the vaccine in the community," said Christie Green, spokeswoman for the Madison County Health Department.
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Madison County has reported 11 confirmed cases of whooping cough since May 17, while seven others were "probable" or "pending."
Green said the department is investigating the outbreak by testing those who have had close contact with the confirmed cases and issuing a round of antibiotics to all of them.
"The possibility exists that within that group of people ... that there still may be some more positive" tests, she said.
The Estill County Health Department has confirmed nine cases and 10 probable cases.
"We're right in the middle of it," said Paula Watson, a health official in Estill County, which borders Madison County.
Watson said the public should know that investigations of the outbreak are a top priority.
"The doctors are doing a wonderful job," she said. "They're testing and starting treatment the same day. All close contacts get treatment."
In an investigation that ended June 4, the Fayette County Health Department found seven confirmed cases of the disease and 12 that were probable. Spokesman Kevin Hall called the numbers "higher than usual;" the county had reported just 31 cases since 2005.
Most children are protected from the disease by a series of immunizations they receive during the first four to six years of life, but state health officials say the increased number of cases could be caused by waning immunities to the vaccination in children older than 10.
Emily Gresham, spokeswoman for the Northern Kentucky Health Department, said whooping cough outbreaks could stem from the difficulty of diagnosing the disease.
"The illness is very mild in adults," she said. "It's a cough that just won't go away. You might not think a lot of it."
Health officials in Northern Kentucky announced Wednesday an outbreak of 38 cases since January, compared to an average of 25 cases a year from 2003 to 2009. The region's last outbreak was in 2010, when 127 cases were reported.
More than half of all cases involving children younger than 12 months result in hospitalization, a fifth result in pneumonia and about 1 percent are fatal, according to the Centers for Disease Control and Prevention.
Green said there's no particular reason for the sudden outbreaks but said doctors, fooled by symptoms, might not be doing the proper tests.
"We might not even realize we have a whooping cough case," she said "It's written off as bronchitis or something like that."
Reported cases nationwide have been increasing steadily since the 1980s, according to the CDC. In 2010, 27,550 cases of whooping cough were reported, the highest since 40,000 were reported in 1959.
Worldwide, the CDC estimates 30 million to 50 million cases and nearly 300,000 deaths a year, mostly in developing countries. According to the CDC, "periodic epidemics and frequent outbreaks" have occurred in recent years.
In 2010, California had the highest number of cases — 9,143 — in 63 years. This year, Washington state has reported 2,325 cases; last year's total was 965.
The New York Times reported in May that some in Washington and Oregon voluntarily exempted their children from one or more vaccines, out of fear of side effects or for philosophical reasons. However, health officials say that does not appear to be a factor in Kentucky.