Pertussis tends to come in waves and poses a quandary for infectious disease control experts, because it could have been eradicated.
So far this year there have been 68 cases in Utah, and last year 1,183 cases were reported. That's down from 2012, when Utah's whooping cough cases reached 1,544, rivaling the pre-vaccination-era levels of the 1940s.
The state's rate of infection that year was higher than the national average, but other states had it worse, including neighboring Colorado, which declared it an epidemic. The Utah Department of Health guidelines define an outbreak as two or more cases in one school within 20 days.
"Pertussis is something we see all year long, not just during cold and flu season," said a Weber-Morgan communicable disease nurse, Amy Carter, in a prepared statement.
The investigation started with the hospitalized infant, who is home now and recovering, said Lori Buttars, spokeswoman for the Weber-Morgan Department of Health. Whooping cough is most dangerous, and lethal, for children under the age of 1 because they're too young to be fully immunized.
In most outbreaks inadequate immunization is the primary culprit. Children entering school are required to be vaccinated against the disease, with five doses of the DTaP vaccine, though some seek waivers.
Some among those exhibiting symptoms in Weber County were fully immunized and some weren't, Buttars said.
A recent study found that the DTaP vaccine may not be as effective as previously thought. It appears to wear off after the fifth dose, which is given between the ages of 4 and 6, making older children more vulnerable, according to the New England Journal of Medicine.
For this reason, the U.S. Centers for Disease Control and Prevention (CDC) recommends booster shots for incoming seventh-graders and for adults as well. Mothers are told to get vaccinated with each pregnancy, and caregivers of infants.
For three years Weber-Morgan has given booster shots at public schools to graduating sixth-graders, who are also invited to bring their siblings.
Whooping cough is a respiratory infection characterized by severe coughing fits. Adults and adolescents may not even realize they have it, believing they have a bad cold or cough.
"We hope that people will continue to take preventive measures and contact their medical provider if they are experiencing sneezing, a runny nose and other cold-like symptoms, especially if they have been exposed to someone who has had a lingering cough," said Carter. "Pertussis symptoms can last as long as three months if left untreated."
People with symptoms should remain home from school, work and other activities until they complete a five-day course of antibiotics. More information can be found www.cdc.gov orwww.immunize.org.