A growing awareness of the booster vaccine, which some middle schools require for entrance, could help stem the tide. In the meantime, both parents and patients still seem surprised when they find out they have whooping cough.
"I didn't think that disease existed anymore," is the response Dr. Judith Guzman-Cottrill, an assistant professor of pediatric infectious disease at Oregon Health and Science University in Portland, often gets when she tells a parent that their child has been diagnosed with pertussis.
And when she tells teenagers they have whooping cough, the typical reaction is "I thought that was a baby disease."
The first stage of the illness typically starts out with a watery, runny nose, sneezing, redness of the eyes, a mild cough, and a low fever for the first week or two. To doctors and parents, it looks very much like the common cold.
The tricky thing about pertussis is that although it resembles a cold in this early stage, this is also when it's most contagious, pointed out Guzman-Cottrill.
But during the second stage, the cough worsens. An infant gets intense coughing fits and brings up thick phlegm. At the end of a severe coughing spell, the baby will try to catch its breath to recover and often takes a long inhalation, which sounds like a whoop. That's where the name whooping cough comes from.
Babies often "whoop," but teens and adults might not. And more than half of patients cough so severely that they vomit afterward.
"The forcefulness of the cough is really dramatic sometimes to the point of rib fracture," said Guzman-Cottrill. Or worse still. Some babies have such severe breathing difficulties that their tiny lungs and heart give out.
When they have whooping cough, infants are most always hospitalized, explained Robert Jacobson, chairman of the department of pediatric and adolescent medicine at the Mayo Clinic. "They look terrible." And infants with pertussis typically get it from adults, he noted.
Compared to younger children, teens and adults don't usually get the classic case of whooping cough and they might not look ill, Jacobson noted. He said they're likely to have an annoying cough that lasts for weeks and weeks.
"That's why it's sometimes called 'the 100-day cough,' which is a great name for it," he said.
Jacobson believes that pertussis is greatly underdiagnosed, and he said his best estimate is that there are about 600,000 cases of it in American adults a year.
Statistics from the CDC, however, paint a very different picture. The CDC reports 10,000 total U.S. cases in 2007, 15,000 cases in 2006 and 25,000 in both 2005 and 2004.
Jacobson also explained that the pertussis bacteria can live in dried mucus for three days, so whooping cough can be a real problem in adults who are undiagnosed and untreated. Adults could potentially pass it on to infants if they are exposed to them in their first few highly contagious weeks of illness, when the respiratory droplets from a cough can propel germs into the air.
According to Jacobson, antibiotics are the typical treatment if the disease is caught early. Antibiotics are also given to family members to reduce the possibility of spreading. He said it's less clear whether antibiotics help with patient symptoms when the disease is diagnosed late.